Cambios inducidos por el Salicilato en la corteza auditiva primaria en gatos no anestesiados.
Zhang X, Yang P, Cao Y, Qin L, Sato Y.
Department of Physiology, China Medical University, and Department of Rheuatology and Immunology, First Affiliated Hospital, Shenyang 110001, PR China.
fuente de la imagen: http://www.notigatos.es/curiosidades-de-gatos-i/
La administración sistémica de salicilatos en dosis altas puede provocar acúfenos e hiperacusia, reversibles en seres humanos y animales.
Por esta razón, una serie de estudios han investigado los cambios inducidos por el salicilato en la actividad neuronal en la corteza auditiva (CA), sin embargo, la mayoría de estudios previos de la CA se llevaron a cabo en cortes de cerebro o en animales anestesiados, que pueden no representar del todo las condiciones reales .
Pocos esfuerzos se han hecho para examinar la actividad neuronal de los animales despiertos, y sólo se registra el potencial del campo local (LFP) de la AC.
En este estudio, se registraron picos de aumemnto de la actividad neuronale en los electrodos implantados en forma permanente en la CA primaria (A1) de gatos despiertos, y se investigan los cambios de la respuesta neuronal a los estímulos de tonos puros y de trenes de clicks, después de la inyección sistémica de 200 mg / kg de salicilato.
Se encontró que el sonido provoca actividades en pico que se incrementan significativamente desde 1 h después de la administración de salicilato, y el aumento de las respuestas neuronales dura más de 3 días con un pico a las 12 h.
el Salicilato no sólo aumentó la amplitud de las respuestas transitorias en el inicio y final de los estímulos de tonos puros, sino que también induce una respuesta sostenida durante el período de estímulo y una respuesta prolongada al final , similar a los 100 ms después de estímulo offset.
El aumento significativo de las respuestas neuronales se observó en el rango de las frecuencias probadas (0,1 a 16 kHz) con un máximo relativo en la banda de 3.2 a 9.6 kHz.
La capacidad de los picos de exhibir sincronización con clics sucesivos mejora también.
Todos estos efectos fueron más evidentes cuando las neuronas fueron estimuladas por sonidos de alta intensidad.
La administración de Salicilato también redujo la tasa espontánea en las unidades de A1, y la disminución de la tasa espontánea fue mayor en las unidades con una frecuencia espontánea alta inicial.
Nuestros datos confirman que el salicilato puede modular la actividad neuronal en la corteza y proporcionan más información para entender el mecanismo de los acúfenos inducidos por salicilato
Fuente :Neuroscience 2011;Vol 172():232 245
Paraguay 2302. Piso 6° "3" Buenos Aires, Capital Federal, Argentina tel/fax +54 11 4771 6228/ +54 11 2066 1908/+54 11 4963 1491 www.acufeno.com, cvirtual@acufeno.com
domingo, 14 de agosto de 2011
Hiperacusia: Sección causas, Lupus eritematoso sistemico
La función auditiva en pacientes con lupus eritematoso sistémico
Autores: Maciaszczyk K, Durko T, Waszczykowska E, Erkiert-Polguj A, Pajor A.
Department of Otolaryngology, Medical University of Lodz, Barlicki University Hospital, Poland. k.maciaszczyk@op.pl
Objetivo: Los pacientes con lupus eritematoso sistémico (LES) pueden desarrollar trastornos de la audición y el equilibrio como resultado del daño inmune en el oído interno debido a la vasculitis o la ototoxicidad de los fármacos utilizados en el tratamiento del LES.
El objetivo del estudio fue la evaluación de los trastornos del órgano de la audición en los pacientes con LES, con especial atención a su prevalencia y su relación con la duración y la gravedad de la enfermedad.
La gravedad se evaluó a partir de la participación de los órganos que dieron lugar a peores resultados ante el LES, es decir, los riñones y el sistema nervioso central (SNC), y de la presencia de anticuerpos asociados con un pronóstico desfavorable LES.
Métodos: Treinta y cinco pacientes no seleccionados y consecutivos (33 mujeres y dos hombres, edad media 47,8 años) con diagnóstico de LES de acuerdo a los criterios internacionales de diagnóstico de la American Rheumatism Association (1982) se incluyeron en el estudio.
El grupo control consistió de 30 personas otologicamente sanos emparejados con el grupo de LES por edad y sexo.
La Historia clinica de cada caso se registró en todos los pacientes junto con los datos del cuestionario y los exámenes que se se realizaron , como audiometria de tonos puros, del habla y la impedancia y potenciales auditivos del tronco cerebral (ABR).
Resultados: En la anamnesis el 71,4% de los pacientes reportaron vértigo, dolores de cabeza 62,9%, 40% tinnitus, hiperacusia 25,7% , 17.1% de pérdida de la audición y el 2,9% sensacion de oído lleno.
Se encontró que los pacientes con LES tuvieron umbrales de audición mas pobres que el grupo control para todas las frecuencias, los umbrales y latencias del ABR estaban prolongados en los pacientes con LES.
Diez pacientes (28,6%) presentaron pérdida auditiva neurosensorial simetrica de alta frecuencias (HNS).
Hay una correlación positiva significativa entre el promedio de los umbrales de audición por vía aérea y la duracion del SLE (r = 0,46, p <0,001) . Después de tomar en consideración la edad, la agudeza auditiva en el LES se relaciona con la duración de la enfermedad en los pacientes más jóvenes. Además, no se observó relación entre el nivel de audición y la gravedad de la enfermedad. Conclusiones: La participación del sistema auditivo debe ser considerado como uno de los elementos del cuadro clínico del lupus eritematoso sistémico, mientras que la determinación de su carácter, original o secundarios, requiere mayor investigación.
Fuente: Auris Nasus Larynx 2011;Vol 38(1):26 32
Autores: Maciaszczyk K, Durko T, Waszczykowska E, Erkiert-Polguj A, Pajor A.
Department of Otolaryngology, Medical University of Lodz, Barlicki University Hospital, Poland. k.maciaszczyk@op.pl
Objetivo: Los pacientes con lupus eritematoso sistémico (LES) pueden desarrollar trastornos de la audición y el equilibrio como resultado del daño inmune en el oído interno debido a la vasculitis o la ototoxicidad de los fármacos utilizados en el tratamiento del LES.
El objetivo del estudio fue la evaluación de los trastornos del órgano de la audición en los pacientes con LES, con especial atención a su prevalencia y su relación con la duración y la gravedad de la enfermedad.
La gravedad se evaluó a partir de la participación de los órganos que dieron lugar a peores resultados ante el LES, es decir, los riñones y el sistema nervioso central (SNC), y de la presencia de anticuerpos asociados con un pronóstico desfavorable LES.
Métodos: Treinta y cinco pacientes no seleccionados y consecutivos (33 mujeres y dos hombres, edad media 47,8 años) con diagnóstico de LES de acuerdo a los criterios internacionales de diagnóstico de la American Rheumatism Association (1982) se incluyeron en el estudio.
El grupo control consistió de 30 personas otologicamente sanos emparejados con el grupo de LES por edad y sexo.
La Historia clinica de cada caso se registró en todos los pacientes junto con los datos del cuestionario y los exámenes que se se realizaron , como audiometria de tonos puros, del habla y la impedancia y potenciales auditivos del tronco cerebral (ABR).
Resultados: En la anamnesis el 71,4% de los pacientes reportaron vértigo, dolores de cabeza 62,9%, 40% tinnitus, hiperacusia 25,7% , 17.1% de pérdida de la audición y el 2,9% sensacion de oído lleno.
Se encontró que los pacientes con LES tuvieron umbrales de audición mas pobres que el grupo control para todas las frecuencias, los umbrales y latencias del ABR estaban prolongados en los pacientes con LES.
Diez pacientes (28,6%) presentaron pérdida auditiva neurosensorial simetrica de alta frecuencias (HNS).
Hay una correlación positiva significativa entre el promedio de los umbrales de audición por vía aérea y la duracion del SLE (r = 0,46, p <0,001) . Después de tomar en consideración la edad, la agudeza auditiva en el LES se relaciona con la duración de la enfermedad en los pacientes más jóvenes. Además, no se observó relación entre el nivel de audición y la gravedad de la enfermedad. Conclusiones: La participación del sistema auditivo debe ser considerado como uno de los elementos del cuadro clínico del lupus eritematoso sistémico, mientras que la determinación de su carácter, original o secundarios, requiere mayor investigación.
Fuente: Auris Nasus Larynx 2011;Vol 38(1):26 32
viernes, 12 de agosto de 2011
Open ear hearing aids in tinnitus therapy: An efficacy comparison with sound generators
Objective: This study aimed to compare the effectiveness of tinnitus retraining therapy (TRT) with sound generators or with open ear hearing aids in the rehabilitation of tinnitus for a group of subjects who, according to Jastreboff categories, can be treated with both approaches to sound therapy (borderline of Category 1 and 2).
Design: This study was a prospective data collection with a parallel-group design which entailed that each subject was randomly assigned to one of the two treatments group: half of the subjects were fitted binaurally with sound generators, and the other half with open ear hearing aids. Both groups received the same educational counselling sessions.
Study sample: Ninety-one subjects passed the screening criteria and were enrolled into the study. Structured interviews, with a variety of measures evaluated through the use of visual-analog scales and the tinnitus handicap inventory self-administered questionnaire, were performed before the therapy and at 3, 6, and 12 months during the therapy.
Results: Data showed a highly significant improvement in both tinnitus treatments starting from the first three months and up to one year of therapy, with a progressive and statistically significant decrease in the disability every three months.
Conclusions: TRT was equally effective with sound generator or open ear hearing aids: they gave basically identical, statistically indistinguishable results.
FUENTE: International Journal of Audiology 2011;Vol 50(8):548 553
Assessment of tinnitus-related impairments and disabilities using the German THI-12: Sensitivity and stability of the scale over time
Objective: To evaluate the reliability, dimensionality, predictive validity, construct validity, and sensitivity to change of the THI-12 total and sub-scales as diagnostic aids to describe and quantify tinnitus-evoked reactions and evaluate treatment efficacy.
Design: Explorative analysis of the German tinnitus handicap inventory (THI-12) to assess potential sensitivity to tinnitus therapy in placebo-controlled randomized studies.
Correlation analysis, including Cronbach's coefficient alpha alpha and explorative common factor analysis (EFA), was conducted within and between assessments to demonstrate the construct validity, dimensionality, and factorial structure of the THI-12.
Study sample: N == 618 patients suffering from subjective tinnitus who were to be screened to participate in a randomized, placebo-controlled, 16-week, longitudinal study.
Results: The THI-12 can reliably diagnose tinnitus-related impairments and disabilities and assess changes over time. The test--retest coefficient for neighboured visits was r > 0.69, the internal consistency of the THI-12 total score was alpha alpha <= 0.79 and alpha alpha <= 0.89 at subsequent visits. Predictability of THI-12 total score and overall variance increased with successive measurements. The three-factorial structure allowed for evaluation of factors that affect aspects of patients'' health-related quality of life. Conclusions: The THI-12, with its three-factorial structure, is a simple, reliable, and valid instrument for the diagnosis and assessment of tinnitus and associated impairment over time.
fuente: International Journal of Audiology 2011;Vol 50(8):523 529
Design: Explorative analysis of the German tinnitus handicap inventory (THI-12) to assess potential sensitivity to tinnitus therapy in placebo-controlled randomized studies.
Correlation analysis, including Cronbach's coefficient alpha alpha and explorative common factor analysis (EFA), was conducted within and between assessments to demonstrate the construct validity, dimensionality, and factorial structure of the THI-12.
Study sample: N == 618 patients suffering from subjective tinnitus who were to be screened to participate in a randomized, placebo-controlled, 16-week, longitudinal study.
Results: The THI-12 can reliably diagnose tinnitus-related impairments and disabilities and assess changes over time. The test--retest coefficient for neighboured visits was r > 0.69, the internal consistency of the THI-12 total score was alpha alpha <= 0.79 and alpha alpha <= 0.89 at subsequent visits. Predictability of THI-12 total score and overall variance increased with successive measurements. The three-factorial structure allowed for evaluation of factors that affect aspects of patients'' health-related quality of life. Conclusions: The THI-12, with its three-factorial structure, is a simple, reliable, and valid instrument for the diagnosis and assessment of tinnitus and associated impairment over time.
fuente: International Journal of Audiology 2011;Vol 50(8):523 529
domingo, 7 de agosto de 2011
Hiperacusia: El efecto del salicilato de sodio
GABAergic neural activity involved in salicylate-induced auditory cortex gain enhancement.
Lu J, Lobarinas E, Deng A, Goodey R, Stolzberg D, Salvi RJ, Sun W.
Source
Center for Hearing and Deafness, State University of New York at Buffalo, 3435 Main Street, NY 14214, USA.
Abstract
Although high doses of sodium salicylate impair cochlear function, it paradoxically enhances sound-evoked activity in the auditory cortex (AC) and augments acoustic startle reflex responses, neural and behavioral metrics associated with hyperexcitability and hyperacusis.
To explore the neural mechanisms underlying salicylate (SS)-induced hyperexcitability and "increased central gain," we examined the effects of GABA receptor agonists and antagonists on SS-induced hyperexcitability in the AC and startle reflex responses.
Consistent with our previous findings, local or systemic application of SS significantly increased the amplitude of sound-evoked AC neural activity, but generally reduced spontaneous activity in the AC.
Systemic injection of SS also significantly increased the acoustic startle reflex. S-baclofen or R-baclofen, GABA-B agonists, which suppressed sound-evoked AC neural firing rate and local field potentials, also suppressed the SS-induced enhancement of the AC field potential and the acoustic startle reflex.
Local application of vigabatrin, which enhances GABA concentration in the brain, suppressed the SS-induced enhancement of AC firing rate.
Systemic injection of vigabatrin also reduced the SS-induced enhancement of acoustic startle reflex.
Collectively, these results suggest that the sound-evoked behavioral and neural hyperactivity induced by SS may arise from a SS-induced suppression of GABAergic inhibition in the AC.
Fuente: Neuroscience. 2011 Aug 25;189:187-98. Epub 2011 Jun 12.
Lu J, Lobarinas E, Deng A, Goodey R, Stolzberg D, Salvi RJ, Sun W.
Source
Center for Hearing and Deafness, State University of New York at Buffalo, 3435 Main Street, NY 14214, USA.
Abstract
Although high doses of sodium salicylate impair cochlear function, it paradoxically enhances sound-evoked activity in the auditory cortex (AC) and augments acoustic startle reflex responses, neural and behavioral metrics associated with hyperexcitability and hyperacusis.
To explore the neural mechanisms underlying salicylate (SS)-induced hyperexcitability and "increased central gain," we examined the effects of GABA receptor agonists and antagonists on SS-induced hyperexcitability in the AC and startle reflex responses.
Consistent with our previous findings, local or systemic application of SS significantly increased the amplitude of sound-evoked AC neural activity, but generally reduced spontaneous activity in the AC.
Systemic injection of SS also significantly increased the acoustic startle reflex. S-baclofen or R-baclofen, GABA-B agonists, which suppressed sound-evoked AC neural firing rate and local field potentials, also suppressed the SS-induced enhancement of the AC field potential and the acoustic startle reflex.
Local application of vigabatrin, which enhances GABA concentration in the brain, suppressed the SS-induced enhancement of AC firing rate.
Systemic injection of vigabatrin also reduced the SS-induced enhancement of acoustic startle reflex.
Collectively, these results suggest that the sound-evoked behavioral and neural hyperactivity induced by SS may arise from a SS-induced suppression of GABAergic inhibition in the AC.
Fuente: Neuroscience. 2011 Aug 25;189:187-98. Epub 2011 Jun 12.
Acúfenos: Sección tratamiento, Estimulación magnetica transcranenana
Short duration repetitive transcranial magnetic stimulation for tinnitus treatment: A prospective Asian study
S.K.S. Tinga Corresponding Author Information e-mail address, Y.M. Chanb, P.W.T. Cheongc, M. Wongb, S. Fook-Chongd, Y.L. Loa
22 March 2011.
Abstract
Background
Tinnitus is a subjective auditory perception of sounds or noise not triggered by external auditory stimuli.
To date, treatment in severe cases is generally unsatisfactory.
Characteristic functional brain imaging changes associated with tinnitus include hyperactivity encompassing both the primary auditory cortex (AC) and the secondary or associative cortex.
Brief repetitive transcranial magnetic stimulation (rTMS) trains applied to the scalp overlying the hyperactive left AC is known to produce moderate tinnitus attenuation.
Objective
Although Western studies have documented the value of rTMS in tinnitus treatment, we evaluate the efficacy of a short duration rTMS protocol for the first time in the Asian setting.
Method
Consecutive patients were recruited at our tinnitus clinic.
Detailed history, examination, audiogram and baseline tinnitus scales were recorded.
RTMS consisted of 1000 pulses/day at 1Hz and 110% of the motor threshold, for five consecutive days over the left temporoparietal cortex. Tinnitus ratings were determined weekly for 4 weeks after rTMS.
Result
Fifteen patients completed the trial; none experienced significant side effects. Repeated measures ANOVA showed significant linear decrease in Tinnitus Handicap Inventory (THI) scores over the time period (F(1,14)=4.7, p=0.04).
However, none of the other parameters (severity, annoyance, effect on lifestyle and overall impression: visual analogue scale) showed beneficial outcomes.
Conclusions
Our findings point to a positive effect of short duration rTMS in tinnitus treatment using the THI.
However, no significant benefits were demonstrated for other subjective patient ratings.
Although well tolerated and convenient, short duration rTMS may prove inadequate for modulating maladaptive plastic changes at the cortical level, and our results suggest the need for delivery of more stimuli.
Future studies will utilize at least 2000 pulses/day, in line with previous experience in Western settings.
Keywords: Tinnitus, Transcranial magnetic stimulation, Asian, Treatment, Trial
a Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
b Department of Otolaryngorhinology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
c Department of Neurology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
d Department of Clinical Research, Singapore General Hospital, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
Corresponding Author Information Corresponding author. Tel.: +65 63265003; fax: +65 62203321.
fuente: Elsevier B.V.
PII: S0303-8467(11)00086-2
doi:10.1016/j.clineuro.2011.03.015
S.K.S. Tinga Corresponding Author Information e-mail address, Y.M. Chanb, P.W.T. Cheongc, M. Wongb, S. Fook-Chongd, Y.L. Loa
22 March 2011.
Abstract
Background
Tinnitus is a subjective auditory perception of sounds or noise not triggered by external auditory stimuli.
To date, treatment in severe cases is generally unsatisfactory.
Characteristic functional brain imaging changes associated with tinnitus include hyperactivity encompassing both the primary auditory cortex (AC) and the secondary or associative cortex.
Brief repetitive transcranial magnetic stimulation (rTMS) trains applied to the scalp overlying the hyperactive left AC is known to produce moderate tinnitus attenuation.
Objective
Although Western studies have documented the value of rTMS in tinnitus treatment, we evaluate the efficacy of a short duration rTMS protocol for the first time in the Asian setting.
Method
Consecutive patients were recruited at our tinnitus clinic.
Detailed history, examination, audiogram and baseline tinnitus scales were recorded.
RTMS consisted of 1000 pulses/day at 1Hz and 110% of the motor threshold, for five consecutive days over the left temporoparietal cortex. Tinnitus ratings were determined weekly for 4 weeks after rTMS.
Result
Fifteen patients completed the trial; none experienced significant side effects. Repeated measures ANOVA showed significant linear decrease in Tinnitus Handicap Inventory (THI) scores over the time period (F(1,14)=4.7, p=0.04).
However, none of the other parameters (severity, annoyance, effect on lifestyle and overall impression: visual analogue scale) showed beneficial outcomes.
Conclusions
Our findings point to a positive effect of short duration rTMS in tinnitus treatment using the THI.
However, no significant benefits were demonstrated for other subjective patient ratings.
Although well tolerated and convenient, short duration rTMS may prove inadequate for modulating maladaptive plastic changes at the cortical level, and our results suggest the need for delivery of more stimuli.
Future studies will utilize at least 2000 pulses/day, in line with previous experience in Western settings.
Keywords: Tinnitus, Transcranial magnetic stimulation, Asian, Treatment, Trial
a Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
b Department of Otolaryngorhinology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
c Department of Neurology, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
d Department of Clinical Research, Singapore General Hospital, Singapore General Hospital, Outram Road, Singapore 169608, Singapore
Corresponding Author Information Corresponding author. Tel.: +65 63265003; fax: +65 62203321.
fuente: Elsevier B.V.
PII: S0303-8467(11)00086-2
doi:10.1016/j.clineuro.2011.03.015
sábado, 6 de agosto de 2011
Acúfenos: Sección causas de acúfenos: Drogas para la hipertension arterial
Prevalence of tinnitus in patients with hypertension and the impact of different anti hypertensive drugs on the incidence of tinnitus: A prospective, single-blind, observational study
MDClaudio Borghi1, MDCristina Brandolini2, MDMaria Grazia Prandin1, MSAda Dormi1, MDGiovanni Carlo Modugno2 and MDAntonio Pirodda2, Corresponding Author Contact Information, E-mail The Corresponding Author
1Department of Internal Medicine, University of Bologna, Bologna, Italy
2Department of Surgical and Anaesthesiological Sciences, University of Bologna, Bologna, Italy
Abstract
Background:
Tinnitus is a common symptom in audiology and neurology patients. Controversial data have been reported in the literature about the prevalence of tinnitus in hypertensive patients, whereas its relationship with the extent of blood pressure (BP) control has not been substantially explored.
Objective:
The aim of this study was to determine the prevalence of tinnitus in hypertensive patients, and the impact of different antihypertensive drugs on the incidence of tinnitus in these patients.
Methods:
This prospective, single-blind, observational study was conducted at the Hypertension Clinic, St. Orsola-Malpighi Hospital, Bologna, Italy.
Patients aged 18 to 75 years with uncontrolled hypertension and receiving antihypertensive therapy were enrolled.
Patients were asked to complete a standardized questionnaire to assess the presence, frequency, and duration of tinnitus and the apparent effect of their antihypertensive treatment on it.
Patients considered by the investigator to have tinnitus, regardless of their audiologic condition, underwent a complete clinical cardiovascular examination, including supine systolic BP (SBP) and diastolic BP measurement and standard 12-lead electrocardiography.
Twelve-hour ambulatory BP monitoring was also performed, and patients were asked to record, using patient diaries, times of the onset and resolution of tinnitus that occurred during those 12 hours.
From these data, correlations between the onset of tinnitus and BP were calculated.
Results:
A total of 476 patients participated in the study (283 men, 193 women).
Of these, 84 (17.6%) patients reported occasional or prolonged spontaneous tinnitus, whereas 392 (82.4%) reported no tinnitus.
The incidence of tinnitus was significantly higher in patients receiving diuretics (72/265 [27.2%]) compared with those receiving angiotensin lI receptor blockers (5/37 [13.5%]), α-blockers (12/55 [21.8%]), or 3-hydroxy-3-methylglutaryl coenzyme
A reduc tase inhibitors (9/73 [12.3%]) (all, P < 0.05). Mean (SD) SBP was significantly higher in patients without tinnitus compared with those with it (143.2 [11.1 ] vs 140.6 [10.3] mm Hg; P < 0.005). In 10 (11.9%) patients with tinnitus, the onset was correlated with a sudden decrease in SBP (<140 mm Hg). Conclusions:
In this study of tinnitus in patients receiving antihypertensivetherapy, tinnitus was found in 17.6% of patients.
Tinnitus was associated with the use of diuretics and with low SBP. Further studies are needed.
Key words: tinnitus; hypertension; diuretics; angiotensin II receptor blockers; α-blockers; 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors
Corresponding Author Contact Information Address correspondence to: Antonio Pirodda, MD, Department of Surgical and Anaesthesiological Sciences, University of Bologna, via Massarenti 9, 40138 Bologna, Italy.
FUENTE:
Current Therapeutic Research
Volume 66, Issue 5, September-October 2005, Pages 420-432
MDClaudio Borghi1, MDCristina Brandolini2, MDMaria Grazia Prandin1, MSAda Dormi1, MDGiovanni Carlo Modugno2 and MDAntonio Pirodda2, Corresponding Author Contact Information, E-mail The Corresponding Author
1Department of Internal Medicine, University of Bologna, Bologna, Italy
2Department of Surgical and Anaesthesiological Sciences, University of Bologna, Bologna, Italy
Abstract
Background:
Tinnitus is a common symptom in audiology and neurology patients. Controversial data have been reported in the literature about the prevalence of tinnitus in hypertensive patients, whereas its relationship with the extent of blood pressure (BP) control has not been substantially explored.
Objective:
The aim of this study was to determine the prevalence of tinnitus in hypertensive patients, and the impact of different antihypertensive drugs on the incidence of tinnitus in these patients.
Methods:
This prospective, single-blind, observational study was conducted at the Hypertension Clinic, St. Orsola-Malpighi Hospital, Bologna, Italy.
Patients aged 18 to 75 years with uncontrolled hypertension and receiving antihypertensive therapy were enrolled.
Patients were asked to complete a standardized questionnaire to assess the presence, frequency, and duration of tinnitus and the apparent effect of their antihypertensive treatment on it.
Patients considered by the investigator to have tinnitus, regardless of their audiologic condition, underwent a complete clinical cardiovascular examination, including supine systolic BP (SBP) and diastolic BP measurement and standard 12-lead electrocardiography.
Twelve-hour ambulatory BP monitoring was also performed, and patients were asked to record, using patient diaries, times of the onset and resolution of tinnitus that occurred during those 12 hours.
From these data, correlations between the onset of tinnitus and BP were calculated.
Results:
A total of 476 patients participated in the study (283 men, 193 women).
Of these, 84 (17.6%) patients reported occasional or prolonged spontaneous tinnitus, whereas 392 (82.4%) reported no tinnitus.
The incidence of tinnitus was significantly higher in patients receiving diuretics (72/265 [27.2%]) compared with those receiving angiotensin lI receptor blockers (5/37 [13.5%]), α-blockers (12/55 [21.8%]), or 3-hydroxy-3-methylglutaryl coenzyme
A reduc tase inhibitors (9/73 [12.3%]) (all, P < 0.05). Mean (SD) SBP was significantly higher in patients without tinnitus compared with those with it (143.2 [11.1 ] vs 140.6 [10.3] mm Hg; P < 0.005). In 10 (11.9%) patients with tinnitus, the onset was correlated with a sudden decrease in SBP (<140 mm Hg). Conclusions:
In this study of tinnitus in patients receiving antihypertensivetherapy, tinnitus was found in 17.6% of patients.
Tinnitus was associated with the use of diuretics and with low SBP. Further studies are needed.
Key words: tinnitus; hypertension; diuretics; angiotensin II receptor blockers; α-blockers; 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors
Corresponding Author Contact Information Address correspondence to: Antonio Pirodda, MD, Department of Surgical and Anaesthesiological Sciences, University of Bologna, via Massarenti 9, 40138 Bologna, Italy.
FUENTE:
Current Therapeutic Research
Volume 66, Issue 5, September-October 2005, Pages 420-432
sábado, 25 de junio de 2011
Audición: Seccion Fisopatologia, estrategias farmacológicas para la prevención del daño coclear
Pharmacological strategies for preventing cochlear damage induced by noise trauma
Barbara Canlon1, Karin Agerman2, Rene Dauman3, Jean-Luc Puel4
1 Department of Physiology and Pharmacolog, Karolinska Institutet, 171 77 Stockholm, Sweden
2 Department of Physiology and Pharmacolog, Karolinska Institutet, 171 77 Stockholm; Department of Molecular Neurobiology, Karolinska Institutet, Stockholm, Sweden
3 Service d´Oto-Rhino-Laryngologie, Unité d´Audiologie, Hospital Pellegrin, C.H.U. de Bordeaux, Bordeau, France
4 INSERM - U. 254, Laboratoire de Neurobiologie de l'Audition, CHU Hôpital St. Charles, Montpellier, France
Abstract
Hearing loss induced by noise, as well as in combination with other environmental factors, is a significant health problem throughout the world.
Although most structures in the inner ear can be harmed by excessive sound exposure, the sensory cells are the most vulnerable.
Damage to the stereocilia bundle is often the first structural alteration noted.
Once a large number of hair cells are lost, the nerve fibres to that region also degenerate resulting in an irreversible hearing loss.
At present, the underlying mechanism for cochlear damage induced by noise is not fully understood.
The failure of the adult peripheral auditory system to regenerate after injury is a major clinical problem.
However, a number of experimental applications have recently become available and are effective in reducing the damaging effects of noise.
Current experimental designs include strategies for protecting against injury and are primarily based on the fact that the metabolic state of the cochlea can determine the overall degree of hearing loss induced by noise.
The purpose of the present article is to review the current literature dealing with strategies for protecting against noise trauma.
Keywords: auditory, cochlea, noise trauma, protection
How to cite this article:
Canlon B, Agerman K, Dauman R, Puel J. Pharmacological strategies for preventing cochlear damage induced by noise trauma. Noise Health 1998;1:13-23
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Canlon B, Agerman K, Dauman R, Puel J. Pharmacological strategies for preventing cochlear damage induced by noise trauma. Noise Health [serial online] 1998 [cited 2011 Jun 25];1:13-23. Available from: http://www.noiseandhealth.org/text.asp?1998/1/1/13/31781
Reducing the damaging effects of noise: The early studies
During the late 70s and early 80s several intriguing experiments demonstrated that the magnitude of hearing loss induced by noise could be modulated.
It was apparent from these early experiments that manipulations of cochlear metabolism directly altered the subsequent damage induced by noise.
Increasing or decreasing body temperature during noise exposure resulted in an increased or decreased cochlear damage (Drescher, 1976; Henry and Chole, 1984).
In addition, increasing the oxygen supply, or removing the thyroid gland was also shown to protect the ear from noise-induced hearing loss (Berndt and Wagner, 1979).
Furthermore, Joachims et al., (1983) studied the effect of magnesium on noise induced hearing thresholds in normotensive rats and spontaneously hypertensive rats and found that magnesium deficiency resulted in a significant increase in the threshold shift in both strains.
All in all, these early experiments demonstrated that the metabolic state of the cochlea could directly determine the overall sensitivity of this organ and provide protection against subsequent noise trauma.
However, this line of experimentation (i.e protecting against injury) was not continued until advances were made in models of brain injury showing protection against neuronal death.
When these demonstrations were successful in the brain similar applications have been made to the cochlea.
Coupling excitotoxicity to noise trauma
Beside the well described changes in stereocilia and hair cells, postsynaptic damage at the synaptic pole of the inner hair cells is also prominent after acoustic trauma.
It entails a disruption of the dendrite ending of the spiral ganglion neurons below the inner hair cells [Figure - 1], leading to synaptic uncoupling (Beagley, 1965; Spoendlin, 1971; Robertson, 1983 ; Pujol, 1990).
Recently, it has been suggested that dendrite damage might be due to excessive release of neurotransmitter from the inner hair cells, which is toxic (excitotoxic) to the structure and function of spiral ganglion neuron (Pujol, 1990).
Consistent with this hypothesis is the high degree of protection against noise trauma that is observed when the glutamate antagonist kynurenate is applied to the cochlea (Puel et al., 1998). Moreover, a synaptic repair mechanism occurring within the first few days post-exposure is partly responsible for the recovery of temporary threshold shifts after an acoustic trauma (Puel et al., 1998).
While the acute synapse disruption primarily depends on alphaa m i n o - 3 - h y d r o x y - 5 - m e t h y l - 4 - isoxazolepropionic acid (AMPA) and kainate type of receptors (Puel et al., 1994), the repair mechanism involved N-methyl-D-aspartate (NMDA) and metabotropic receptors (Puel et al., 1995; d'Aldin et al., 1997).
This regenerative process does not exclude the possibility that in the case of successive excitotoxic injuries, additive effects could irreversibly damage some neurons, and consequently lower or stop the beneficial effects of re-innervation.
In support of this line of argument, glutamate neurotoxicity has been reported in the developing rat cochlea after systemic administration of glutamate (Janssen et al., 1991).
L-glutamate administered intraperitoneally to developing rats on postnatal days 2 to 9 produced high-frequency threshold elevations.
The major site of peripheral damage was the spiral ganglion neurons in the basal region of the cochlea, where a significant reduction in neurons was noted.
Scanning electron micrographs of surface preparations revealed no significant hair cell death.
Similarly, Juiz et al. (1989) reported that 10 days or more after an intracochlear perfusion of kainate, a subpopulation of spiral ganglion neurons (34%) had degenerated with no apparent damage to cochlear hair cells and supporting cells.
In agreement with the reported selectivity of kainate for glutamaceptive neurons (Coyle, 1983), the neuronal loss induced by kainate was in vitro blocked by the broad spectrum glutamatergic antagonist kynurenate, in a dosedependent manner (Lefebvre et al., 1991). The pathological consequences of sound-induced excitotoxicity is summarised in [Figure - 1].
Coupling NMDA receptors to NO synthesis for noise trauma
The administration of N-methyl-D-aspartate (NMDA) antagonists have been shown to prevent toxic damage to hair cells in guinea pigs treated with aminoglycoside antibiotics (Basil et al., 1996).
It was suggested that the aminoglycosides bind to the polyamine site on the NMDA receptor and by excitotoxic mechanisms results in the destruction of the hair cells.
Regardless of whether hair cells express NMDA receptors, why are the spiral ganglion neurons spared, which certainly express these receptors?
One explanation that has been proposed is that aminoglycoside activation of NMDA receptors on neurons is not lethal by itself, but causes the release of other toxic substances from neurons which in turn damage the cells in the organ of Corti (Ernfors and Canlon, 1996).
Nitric oxide (NO) is a typical retrograde signal in the brain and the concentration at which it is present determines whether it has protective or toxic effects.
Furthermore, NO has been shown to be one of the underlying molecules involved in the cell death following NMDA-mediated excitotic damage in the CNS.
It is possible that NO is a mediator of hair cell damage in the cochlea because: (i) at high concentrations NO causes the death of any type of cell (thus both hair cells and supporting cells would succumb to it), (ii) it is produced by the spiral ganglion neurons (iii) it is known that excess stimulation of NMDA receptors leads to excess NO release, and (iv) by blocking NO synthesis in the cochlea with the inhibitor NG-methyl-L-arginine prevents chemically induced cytotoxicity.
The overproduction of NO would be expected to damage all cell types in the organ of Corti and the NO hypothesis could explain the loss of both hair cells and supporting cells following severe noise damage.
Any toxic effect from the neurons to the hair cells in the organ of Corti are most likely in balance with protective mechanisms also stemming from the spiral ganglion neurons.
Rapid production of oxygen free radicals in hair cells have been implicated in hearing loss induced by noise (Quirk et al., 1994; Yamane et al., 1995; Seidman et al., 1993).
An upregulation of anti-oxidant enzymes in cochlear tissues have been demonstrated after noise exposure (Jacono et al., 1998).
The upregulation of these enzymes would be expected to attenuate threshold shifts induced by noise exposure.
The susceptibility of the cochlea to noise-induced damage is increased by inhibition of glutathione synthesis (Yamasoba et al., 1998).
These increased thresholds were found after a noise exposure that was repeated for several days. However, when a short term noise exposure was investigated, whole tissue levels of glutathione were not altered suggesting that short duration noise exposure does not alter glutathione homeostasis (Lautermann et al., 1997).
It is not enough to just block the NMDA receptors but rather a combined treatment with for example, NMDA receptor blockers, and antioxidant therapy can protect against noise induced hearing loss.
Sound conditioning
A number of recent studies have shown that the susceptibility of the inner ear to noise trauma can be reduced by prior exposure to an acoustic stimulus.
At present, two distinct paradigms are employed to reduce the susceptibility of the inner ear to noise trauma.
The first uses a lowlevel, non-damaging continuous acoustic stimulus before the traumatic exposure [Figure - 2]. This phenomenon has been termed sound "conditioning" and has been demonstrated on a number of species including guinea pigs, gerbils, rabbits, and rats (Canlon et al., 1988; Ryan et al., 1994; Boettcher et al. 1995; Dagli and Canlon, 1994; 1997, Kujawa and Liberman, 1997; Canlon et al., 1992; Pukkila et al., 1997; White et al., 1998).
The second paradigm uses an interrupted schedule at sound levels that produce a temporary threshold shift during the first few days of exposure.
However, as the daily exposure continues the degree of threshold shift is reduced, in some cases to no threshold shift despite an ongoing exposure.
This reduction has been termed "toughening" or resistance to noiseinduced hearing loss.
Toughening has been demonstrated in chinchillas, guinea pigs, and gerbils (Clark et al., 1987; Sinex et al., 1987; Campo et al., 1991; Franklin et al., 1991; Boettcher, et al., 1992, 1993; Subramaniam et al 1991, Miyakita et al., 1992; Boettcher, 1993; Henselman et al., 1994; Henderson et al., 1994; McFadden et al., 1997; White et al., 1998).
While the underlying mechanism responsible for protection against noise trauma by sound conditioning is not known, neither the middle ear muscles, nor the efferent system seems to play a significant role.
Studies from three different laboratories, using three different species, have shown that the middle ear muscles do not significantly contribute to the protection from acoustic trauma by sound conditioning (Ryan et al., 1994; Henderson et al., 1994, and Dagli and Canlon, 1995).
The role the efferents play in modulating noise damage after sound conditioning is questioned after a report that compared a sham operated sound conditioned group to a deefferented sound conditioned group and showed similar responses to the traumatic stimulus.
It was suggested that stress factors play a significant role in determining the sensitivity of the ear to trauma.
Noise and other types of stress, for example, restraint, have been shown to increase glucocorticoid levels (Rarey et al., 1995; Curtis and Rarey 1995).
An interesting study by Jacono et al. (1998) has shown that a sound conditioning paradigm caused an increase in antioxidant systems.
The finding that low level acoustic stimulation increases endogenous levels of antioxidant systems in the cochlea opens many new avenues for future studies on protecting against noise trauma.
Could the sound-induced increase in endogenous antioxidant systems provide protection against other environmental toxins? Future experiments are needed to address this question.
Pharmacological Studies
Reactive oxygen species are implicated in a variety of hearing disorders.
The ultimate fate of free radicals is the induction of membrane lipid peroxidation which leads to alteration in ion homeostasis and energy metabolism and eventual destruction of the plasma membrane.
The subcellular source of oxyradicals is the mitochondria where oxygen radicals are generated during the electron-transport process.
Two oxyradicals that play predominant roles as initiators of membrane lipid peroxidation are the hydroxyl radical and peroxynitrite.
The hydroxyl radical can also interact with nitric oxide to form peroxynitrite. These processes occur in many different acute and chronic degenerative conditions and can lead to a cascade of events that culminate in apoptotic cell death.
The inhibition of free radical generation (antioxidative processes) can protect the membrane from damage and can maintain ion homeostasis and cellular energy metabolism.
Noise and ototoxic drugs affect inner ear function, possibly through free radicals, and are therefore expected to affect cellular defence mechanisms.
Glutathione, an endogenous antioxidant substance, that has been localised primarily to the stria vascularis, has been shown to protect against noise trauma.
The antioxidant system is sensitive towards environmental influences and show differences in cochlear glutathione and glutathione-related enzymes in different species. (Lautermann et al., 1997).
Gentamicin ototoxicity has been shown to depend on dietary factors and to correlate with tissue glutathione levels (Lautermann e al., 1995).
Thus, compounds that could potentially protect against gentamicin ototoxicity may be more correctly assessed in animal models of deficient nutritional states in which endogenous detoxifying mechanisms are compromised.
The inhibition of the generation of reactive oxygen species has been a successful means of protecting against noise-induced hearing loss (Seidman et al., 1993; Quirk et al., 1994; Yamane et al., 1995; Jacono et al., 1998; Yamasoba et al., 1998).
Reduced cochlear blood flow by vasoconstriction has been implicated in noiseinduced hearing loss (Hawkins, 1971).
Ohlsen et al has shown the effectiveness of topical application of vasodilating agents in increasing cochlear blood flow (Ohlsen et al., 1992).
Others have shown that oxygen (i.e. cochlearoxygenation) is a more important factor than CO2 (i.e., as a vasodilator) in protection of the cochlea from noise induced damage (Hatch et al., 1991).
Experiments where all calcium channels were blocked caused a reduction in noise-induced microvascular permeability which in turn can reduce temporary threshold shifts (Goldwyn et al., 1997).
Exposure of noise to the cochlea may result in local vasoconstriction of cochlear vessels, which leads to a decrease in cochlear blood.
This may lead to hypoxia and subsequently formation of free oxygen radicals. Seidman et al have shown that both superoxide dismutase and allopurinol can prevent noise-induced damage, indicating that this damage may be related to free oxygen radicals (Seidman et al., 1993).
Other experiments show that free oxygen radical induced lipid peroxidation is an important mechanism in noise-induced hearing loss (Quirk et al., 1994).
Acoustic trauma and tinnitus
Worthy of note is the frequent occurrence of tinnitus (i.e. auditory perception in absence of sound stimulation) and the overexpression of NMDA receptors after an acoustic trauma (Axelsson and Barrenas, 1991, Puel et al., 1996).
In contrast to AMPA/kainate receptors that simply mediate fast depolarising responses, activation of NMDA receptors can result in longlasting changes in synaptic efficacy, responsible for the induction of long-term potentiation (LTP). Briefly, LTP is a sustained increase in synaptic efficacy following tetanic stimulation of some excitatory pathways, and has attracted wide interest as a potential mechanism for information storage in the brain (i.e. learning and memory).
Although the precise mechanisms underlying this form of plasticity are unknown, NMDA receptor antagonists have been shown to prevent its induction in hippocampal pathways, even though these substances have little effect on excitatory postsynaptic potentials (EPSPs) (see Collingridge et al., 1988).
Subsequent investigations have also demonstrated that NMDA receptor antagonists can suppress epileptiform activity (paroxysmal depolarisations, burst firing) induced in vitro by convulsant drugs, and by kindling-like electrical stimulation, and can block convulsions in many animals models of epilepsy (Dingledine et al., 1990 ; Chapman, 1991).
Thus, one speculation is that, if altered, or excessively stimulated (e.g. resulting from ischaemia/acoustic trauma), NMDA receptors in the cochlea also could give rise to an increased spontaneous and repetitive or "epileptic-like" firing, which could be interpreted as tinnitus by the brain auditory centres.
At first glance, treatment with glutamate antagonists that alter neurotransmission does not seem appropriate to treat hearing loss and tinnitus.
Interestingly, NMDA and metabotropic receptors that appear to be an important component in pathological conditions (i.e, neosynaptogenesis, tinnitus, neuronal death), are those involved to a lesser degree in excitatory synaptic function, making them an attractive therapeutic target.
Another neuropharmacological approach for pathologies linked to glutamate excitotoxicity might also take into account the pharmacology of some lateral efferent agonists.
Numerous neuroactive substances have been found in these synapses: ACh, GABA, dopamine, encephalins, dynorphins, and CGRP (see Eybalin, 1993).
Once again, these molecules, which have limited effects on the normal functioning of the cochlea, are released under pathological conditions such as noise (Drescher et al., 1983 ; Eybalin et al., 1987b, Gil Loyzaga et al., 1993), and could be involved in synaptic plasticity such as the guidance of newly formed dendrites and/or the stabilisation of the IHC synapses (Puel et al., 1995).
Clinical Considerations
What is clear at this point is that there is much work to be done before the above pharmacological speculations can be put into clinical practice.
Future research that relies on molecular information, such as antisense oligonucleotide experiments, knockout strategies, and gene transfer protocols, is still necessary to better understand both physiological and pathological mechanisms underlying synaptic plasticity, control of neuronal excitability, and neuronal death.
Indeed, it is reasonable to assume that subtle molecular mechanisms involved in cochlear function and disease will be more clearly understood in the near future, there are certain restrictions that have to be taken into account for their possible clinical application.
Since the hair cells of the mammalian cochlea do not have the ability to regenerate, we are only left with the hope of finding effective intervention therapies.
A possible concern here is whether, in the therapeutic dose range, these products will cause side effect on the central functions.
Addressing these questions will require the development of a local application of drugs directly into the cochlea.
However, before intervention therapies can be implemented several issues concerning the choice of patients, the route of administration, and the choice of drugs to be applied needs to be determined.
It would be best to reserve in situ cochlear pharmacology for those patients with a normal contralateral ear or with an ear that can easily be fitted with a hearing device.
Decision for the best route of administration will be partially governed by the techniques routinely used in the clinic, and partially by economic soundness.
Two possibilities include an extra-cochlear approach (round or oval window), or, to a direct, intracochlear administration.
The extra-cochlear approach has several disadvantages compared to the intra-cochlear administration. It is most conceivable that the extra-cochlear approach, an invasive operation, will be a one-time procedure.
Taking into the consideration the rapid turnover of perilymph, the therapy drug will be quickly diluted and removed from the perilymph.
As a result of the rapid perilymph turnover, this route of administration may not offer any substantial benefit.
Repeated application would therefore be necessary, but would be unpractical.
It is most likely that cochlear implant patients will have a major role to play in the development of in situ cochlear pharmacology.
The simultaneous implantation of both the cochlear implant electrodes together with a mini-osmotic pump would be possible and the mini-osmotic pump could allow for continuous infusion for weeks.
Even if longer infusion times are required a simple procedure to refill the osmotic pump is all that would be required.
Continued animal experiments are necessary for determining the drug of choice or a combination of drugs as well as their appropriate concentrations. At present, little is known about the long-term effects of drug therapy.
Most animal experiments have ended after either two or four weeks and it is therefore important to gain more information about longer survival times (years) for the morphology and physiology of the hair cells and spiral ganglion neurons.
Conclusions
Our understanding of cochlear protective mechanisms has made significant advances in recent years.
These results have led to new concepts for the homeostasis of the cochlea.
These new concepts consider that the balance of retrograde and anterograde trophic signalling factors determines the overall susceptibility of organ of Corti and spiral ganglion neurons to damage, as schematically shown in [Figure - 3] (Ernfors and Canlon, 1996).
Compromising the organ of Corti will deplete spiral ganglion neurons of neurotrophic support and will eventually result in the death of these cells and disrupting the neurons should deprive hair cells of trophic support causing cell death.
Regardless of the mechanisms of action and whether the effects are direct or not, the fact of the matter is that a giant leap has been made for preventing neuronal and organ of Corti damage and now there are candidate drugs with protective properties for spiral ganglion neurons as well as for cochlear hair cells.
It is conceivable that clinical trials can be performed in the near future and new strategies for preventing hearing loss established.
Acknowledgements
This study was supported by grants from the Swedish Council for Work Life Research (79-0800), Medical Research Council (09476), Stiftelsen Tysta Skolan, and the Karolinska Institute. A joint publication of PAN partners (European Commission BIOMED 2 concerted action - Contract BMH 4-CT96-0110).[66]
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56. Pukkila, M., Zhai, S., Virkkala, J., Pirovola, U., and Ylikoski, J. (1997) The "toughening" phenomenon in rat´s auditory organ. Acta Otolaryngol. 529:59-62. Back to cited text no. 56
57. Quirk W.S., Shivapuja B.G., Schwimmer C.L., Seidman M..D. (1994) Lipid peroxidation inhibitor attenuates noise-induced temporary threshold shifts. Hear Res 74, 217-220. Back to cited text no. 57
58. Rarey, K.E., Gerhardt, K.J., Curtis, L.M., and ten Cate, W.J-F. (1995) Effect of stress on cochlear glucocorticoid protein: acoustic stress. Hear. Res. 82: 135-138. Back to cited text no. 58
59. Robertson, D. (1983) Functional significance of dendritic swelling after loud sounds in the guinea pig cochlea. Hear. Res. 9, 263-278. Back to cited text no. 59
60. Ryan, A.F., Bennett, T.M., Woolf, N.K., and Axelsson, A. (1994). Protection from noise-induced hearing loss by prior exposure to a nontraumatic stimulus: Role of the middle ear muscles, Hear. Res. 72, 23-28. Back to cited text no. 60
61. Seidman, M.D., Shivapuja, B.G., and Quirk, W.S. (1993) The protective effects of allopurinol and superoxide dismutase on noise-induced cochlear damage. Otolaryngol. Head Neck Surg. 109, 1052-1056. Back to cited text no. 61
62. Sinex, D.G., Clark, W.W., and Bohne, B.A. (1987). Effect of periodic rest on physiological measures of auditory sensitivity following exposure to noise, J. Acoust. Soc. Am. 82, 1265-1273. Back to cited text no. 62
63. Spoendlin, H. (1971) Primary structural changes in the organ of Corti after acoustic overstimulation. Acta Otolaryngol (Stockh). 71, 166-176. Subramaniam, M., Campo, P., and Henderson, D. (1991) The effect of exposure level on the development of progressive resistance to noise. Hear. Res. 52, 181-188. Back to cited text no. 63
64. White DR, Boettcher FA, Miles LR, Gratton MA (1998) Effectiveness of intermittent and continuous acoustic stimulation in preventing noise-induced hearing and hair cell loss. J. Acoust Soc Am 103(3):1566-1572. Back to cited text no. 64
65. Yamane, H., Nakai, Y., Takayama, M., Konishi, K., Iguchi, H., Nakagawa, T., Shibata, S., Kato, A., Sunami, K., and Kawakatsu, C. (1995) The emergence of free radicals after acoustic trauma and strial blood flow. Acta Otolaryngol 519, 87-92. Back to cited text no. 65
66. Yamasoba T., Nuttall A.L., Harris, C., Raphael, Y., Miller, J.M. (1998) Role of glutathione in protection against noise-induced hearing loss. Brain Res. 784, 82-90. Back to cited text no. 66
Fuente: http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=1998;volume=1;issue=1;spage=13;epage=23;aulast=Canlon
Barbara Canlon1, Karin Agerman2, Rene Dauman3, Jean-Luc Puel4
1 Department of Physiology and Pharmacolog, Karolinska Institutet, 171 77 Stockholm, Sweden
2 Department of Physiology and Pharmacolog, Karolinska Institutet, 171 77 Stockholm; Department of Molecular Neurobiology, Karolinska Institutet, Stockholm, Sweden
3 Service d´Oto-Rhino-Laryngologie, Unité d´Audiologie, Hospital Pellegrin, C.H.U. de Bordeaux, Bordeau, France
4 INSERM - U. 254, Laboratoire de Neurobiologie de l'Audition, CHU Hôpital St. Charles, Montpellier, France
Abstract
Hearing loss induced by noise, as well as in combination with other environmental factors, is a significant health problem throughout the world.
Although most structures in the inner ear can be harmed by excessive sound exposure, the sensory cells are the most vulnerable.
Damage to the stereocilia bundle is often the first structural alteration noted.
Once a large number of hair cells are lost, the nerve fibres to that region also degenerate resulting in an irreversible hearing loss.
At present, the underlying mechanism for cochlear damage induced by noise is not fully understood.
The failure of the adult peripheral auditory system to regenerate after injury is a major clinical problem.
However, a number of experimental applications have recently become available and are effective in reducing the damaging effects of noise.
Current experimental designs include strategies for protecting against injury and are primarily based on the fact that the metabolic state of the cochlea can determine the overall degree of hearing loss induced by noise.
The purpose of the present article is to review the current literature dealing with strategies for protecting against noise trauma.
Keywords: auditory, cochlea, noise trauma, protection
How to cite this article:
Canlon B, Agerman K, Dauman R, Puel J. Pharmacological strategies for preventing cochlear damage induced by noise trauma. Noise Health 1998;1:13-23
How to cite this URL:
Canlon B, Agerman K, Dauman R, Puel J. Pharmacological strategies for preventing cochlear damage induced by noise trauma. Noise Health [serial online] 1998 [cited 2011 Jun 25];1:13-23. Available from: http://www.noiseandhealth.org/text.asp?1998/1/1/13/31781
Reducing the damaging effects of noise: The early studies
During the late 70s and early 80s several intriguing experiments demonstrated that the magnitude of hearing loss induced by noise could be modulated.
It was apparent from these early experiments that manipulations of cochlear metabolism directly altered the subsequent damage induced by noise.
Increasing or decreasing body temperature during noise exposure resulted in an increased or decreased cochlear damage (Drescher, 1976; Henry and Chole, 1984).
In addition, increasing the oxygen supply, or removing the thyroid gland was also shown to protect the ear from noise-induced hearing loss (Berndt and Wagner, 1979).
Furthermore, Joachims et al., (1983) studied the effect of magnesium on noise induced hearing thresholds in normotensive rats and spontaneously hypertensive rats and found that magnesium deficiency resulted in a significant increase in the threshold shift in both strains.
All in all, these early experiments demonstrated that the metabolic state of the cochlea could directly determine the overall sensitivity of this organ and provide protection against subsequent noise trauma.
However, this line of experimentation (i.e protecting against injury) was not continued until advances were made in models of brain injury showing protection against neuronal death.
When these demonstrations were successful in the brain similar applications have been made to the cochlea.
Coupling excitotoxicity to noise trauma
Beside the well described changes in stereocilia and hair cells, postsynaptic damage at the synaptic pole of the inner hair cells is also prominent after acoustic trauma.
It entails a disruption of the dendrite ending of the spiral ganglion neurons below the inner hair cells [Figure - 1], leading to synaptic uncoupling (Beagley, 1965; Spoendlin, 1971; Robertson, 1983 ; Pujol, 1990).
Recently, it has been suggested that dendrite damage might be due to excessive release of neurotransmitter from the inner hair cells, which is toxic (excitotoxic) to the structure and function of spiral ganglion neuron (Pujol, 1990).
Consistent with this hypothesis is the high degree of protection against noise trauma that is observed when the glutamate antagonist kynurenate is applied to the cochlea (Puel et al., 1998). Moreover, a synaptic repair mechanism occurring within the first few days post-exposure is partly responsible for the recovery of temporary threshold shifts after an acoustic trauma (Puel et al., 1998).
While the acute synapse disruption primarily depends on alphaa m i n o - 3 - h y d r o x y - 5 - m e t h y l - 4 - isoxazolepropionic acid (AMPA) and kainate type of receptors (Puel et al., 1994), the repair mechanism involved N-methyl-D-aspartate (NMDA) and metabotropic receptors (Puel et al., 1995; d'Aldin et al., 1997).
This regenerative process does not exclude the possibility that in the case of successive excitotoxic injuries, additive effects could irreversibly damage some neurons, and consequently lower or stop the beneficial effects of re-innervation.
In support of this line of argument, glutamate neurotoxicity has been reported in the developing rat cochlea after systemic administration of glutamate (Janssen et al., 1991).
L-glutamate administered intraperitoneally to developing rats on postnatal days 2 to 9 produced high-frequency threshold elevations.
The major site of peripheral damage was the spiral ganglion neurons in the basal region of the cochlea, where a significant reduction in neurons was noted.
Scanning electron micrographs of surface preparations revealed no significant hair cell death.
Similarly, Juiz et al. (1989) reported that 10 days or more after an intracochlear perfusion of kainate, a subpopulation of spiral ganglion neurons (34%) had degenerated with no apparent damage to cochlear hair cells and supporting cells.
In agreement with the reported selectivity of kainate for glutamaceptive neurons (Coyle, 1983), the neuronal loss induced by kainate was in vitro blocked by the broad spectrum glutamatergic antagonist kynurenate, in a dosedependent manner (Lefebvre et al., 1991). The pathological consequences of sound-induced excitotoxicity is summarised in [Figure - 1].
Coupling NMDA receptors to NO synthesis for noise trauma
The administration of N-methyl-D-aspartate (NMDA) antagonists have been shown to prevent toxic damage to hair cells in guinea pigs treated with aminoglycoside antibiotics (Basil et al., 1996).
It was suggested that the aminoglycosides bind to the polyamine site on the NMDA receptor and by excitotoxic mechanisms results in the destruction of the hair cells.
Regardless of whether hair cells express NMDA receptors, why are the spiral ganglion neurons spared, which certainly express these receptors?
One explanation that has been proposed is that aminoglycoside activation of NMDA receptors on neurons is not lethal by itself, but causes the release of other toxic substances from neurons which in turn damage the cells in the organ of Corti (Ernfors and Canlon, 1996).
Nitric oxide (NO) is a typical retrograde signal in the brain and the concentration at which it is present determines whether it has protective or toxic effects.
Furthermore, NO has been shown to be one of the underlying molecules involved in the cell death following NMDA-mediated excitotic damage in the CNS.
It is possible that NO is a mediator of hair cell damage in the cochlea because: (i) at high concentrations NO causes the death of any type of cell (thus both hair cells and supporting cells would succumb to it), (ii) it is produced by the spiral ganglion neurons (iii) it is known that excess stimulation of NMDA receptors leads to excess NO release, and (iv) by blocking NO synthesis in the cochlea with the inhibitor NG-methyl-L-arginine prevents chemically induced cytotoxicity.
The overproduction of NO would be expected to damage all cell types in the organ of Corti and the NO hypothesis could explain the loss of both hair cells and supporting cells following severe noise damage.
Any toxic effect from the neurons to the hair cells in the organ of Corti are most likely in balance with protective mechanisms also stemming from the spiral ganglion neurons.
Rapid production of oxygen free radicals in hair cells have been implicated in hearing loss induced by noise (Quirk et al., 1994; Yamane et al., 1995; Seidman et al., 1993).
An upregulation of anti-oxidant enzymes in cochlear tissues have been demonstrated after noise exposure (Jacono et al., 1998).
The upregulation of these enzymes would be expected to attenuate threshold shifts induced by noise exposure.
The susceptibility of the cochlea to noise-induced damage is increased by inhibition of glutathione synthesis (Yamasoba et al., 1998).
These increased thresholds were found after a noise exposure that was repeated for several days. However, when a short term noise exposure was investigated, whole tissue levels of glutathione were not altered suggesting that short duration noise exposure does not alter glutathione homeostasis (Lautermann et al., 1997).
It is not enough to just block the NMDA receptors but rather a combined treatment with for example, NMDA receptor blockers, and antioxidant therapy can protect against noise induced hearing loss.
Sound conditioning
A number of recent studies have shown that the susceptibility of the inner ear to noise trauma can be reduced by prior exposure to an acoustic stimulus.
At present, two distinct paradigms are employed to reduce the susceptibility of the inner ear to noise trauma.
The first uses a lowlevel, non-damaging continuous acoustic stimulus before the traumatic exposure [Figure - 2]. This phenomenon has been termed sound "conditioning" and has been demonstrated on a number of species including guinea pigs, gerbils, rabbits, and rats (Canlon et al., 1988; Ryan et al., 1994; Boettcher et al. 1995; Dagli and Canlon, 1994; 1997, Kujawa and Liberman, 1997; Canlon et al., 1992; Pukkila et al., 1997; White et al., 1998).
The second paradigm uses an interrupted schedule at sound levels that produce a temporary threshold shift during the first few days of exposure.
However, as the daily exposure continues the degree of threshold shift is reduced, in some cases to no threshold shift despite an ongoing exposure.
This reduction has been termed "toughening" or resistance to noiseinduced hearing loss.
Toughening has been demonstrated in chinchillas, guinea pigs, and gerbils (Clark et al., 1987; Sinex et al., 1987; Campo et al., 1991; Franklin et al., 1991; Boettcher, et al., 1992, 1993; Subramaniam et al 1991, Miyakita et al., 1992; Boettcher, 1993; Henselman et al., 1994; Henderson et al., 1994; McFadden et al., 1997; White et al., 1998).
While the underlying mechanism responsible for protection against noise trauma by sound conditioning is not known, neither the middle ear muscles, nor the efferent system seems to play a significant role.
Studies from three different laboratories, using three different species, have shown that the middle ear muscles do not significantly contribute to the protection from acoustic trauma by sound conditioning (Ryan et al., 1994; Henderson et al., 1994, and Dagli and Canlon, 1995).
The role the efferents play in modulating noise damage after sound conditioning is questioned after a report that compared a sham operated sound conditioned group to a deefferented sound conditioned group and showed similar responses to the traumatic stimulus.
It was suggested that stress factors play a significant role in determining the sensitivity of the ear to trauma.
Noise and other types of stress, for example, restraint, have been shown to increase glucocorticoid levels (Rarey et al., 1995; Curtis and Rarey 1995).
An interesting study by Jacono et al. (1998) has shown that a sound conditioning paradigm caused an increase in antioxidant systems.
The finding that low level acoustic stimulation increases endogenous levels of antioxidant systems in the cochlea opens many new avenues for future studies on protecting against noise trauma.
Could the sound-induced increase in endogenous antioxidant systems provide protection against other environmental toxins? Future experiments are needed to address this question.
Pharmacological Studies
Reactive oxygen species are implicated in a variety of hearing disorders.
The ultimate fate of free radicals is the induction of membrane lipid peroxidation which leads to alteration in ion homeostasis and energy metabolism and eventual destruction of the plasma membrane.
The subcellular source of oxyradicals is the mitochondria where oxygen radicals are generated during the electron-transport process.
Two oxyradicals that play predominant roles as initiators of membrane lipid peroxidation are the hydroxyl radical and peroxynitrite.
The hydroxyl radical can also interact with nitric oxide to form peroxynitrite. These processes occur in many different acute and chronic degenerative conditions and can lead to a cascade of events that culminate in apoptotic cell death.
The inhibition of free radical generation (antioxidative processes) can protect the membrane from damage and can maintain ion homeostasis and cellular energy metabolism.
Noise and ototoxic drugs affect inner ear function, possibly through free radicals, and are therefore expected to affect cellular defence mechanisms.
Glutathione, an endogenous antioxidant substance, that has been localised primarily to the stria vascularis, has been shown to protect against noise trauma.
The antioxidant system is sensitive towards environmental influences and show differences in cochlear glutathione and glutathione-related enzymes in different species. (Lautermann et al., 1997).
Gentamicin ototoxicity has been shown to depend on dietary factors and to correlate with tissue glutathione levels (Lautermann e al., 1995).
Thus, compounds that could potentially protect against gentamicin ototoxicity may be more correctly assessed in animal models of deficient nutritional states in which endogenous detoxifying mechanisms are compromised.
The inhibition of the generation of reactive oxygen species has been a successful means of protecting against noise-induced hearing loss (Seidman et al., 1993; Quirk et al., 1994; Yamane et al., 1995; Jacono et al., 1998; Yamasoba et al., 1998).
Reduced cochlear blood flow by vasoconstriction has been implicated in noiseinduced hearing loss (Hawkins, 1971).
Ohlsen et al has shown the effectiveness of topical application of vasodilating agents in increasing cochlear blood flow (Ohlsen et al., 1992).
Others have shown that oxygen (i.e. cochlearoxygenation) is a more important factor than CO2 (i.e., as a vasodilator) in protection of the cochlea from noise induced damage (Hatch et al., 1991).
Experiments where all calcium channels were blocked caused a reduction in noise-induced microvascular permeability which in turn can reduce temporary threshold shifts (Goldwyn et al., 1997).
Exposure of noise to the cochlea may result in local vasoconstriction of cochlear vessels, which leads to a decrease in cochlear blood.
This may lead to hypoxia and subsequently formation of free oxygen radicals. Seidman et al have shown that both superoxide dismutase and allopurinol can prevent noise-induced damage, indicating that this damage may be related to free oxygen radicals (Seidman et al., 1993).
Other experiments show that free oxygen radical induced lipid peroxidation is an important mechanism in noise-induced hearing loss (Quirk et al., 1994).
Acoustic trauma and tinnitus
Worthy of note is the frequent occurrence of tinnitus (i.e. auditory perception in absence of sound stimulation) and the overexpression of NMDA receptors after an acoustic trauma (Axelsson and Barrenas, 1991, Puel et al., 1996).
In contrast to AMPA/kainate receptors that simply mediate fast depolarising responses, activation of NMDA receptors can result in longlasting changes in synaptic efficacy, responsible for the induction of long-term potentiation (LTP). Briefly, LTP is a sustained increase in synaptic efficacy following tetanic stimulation of some excitatory pathways, and has attracted wide interest as a potential mechanism for information storage in the brain (i.e. learning and memory).
Although the precise mechanisms underlying this form of plasticity are unknown, NMDA receptor antagonists have been shown to prevent its induction in hippocampal pathways, even though these substances have little effect on excitatory postsynaptic potentials (EPSPs) (see Collingridge et al., 1988).
Subsequent investigations have also demonstrated that NMDA receptor antagonists can suppress epileptiform activity (paroxysmal depolarisations, burst firing) induced in vitro by convulsant drugs, and by kindling-like electrical stimulation, and can block convulsions in many animals models of epilepsy (Dingledine et al., 1990 ; Chapman, 1991).
Thus, one speculation is that, if altered, or excessively stimulated (e.g. resulting from ischaemia/acoustic trauma), NMDA receptors in the cochlea also could give rise to an increased spontaneous and repetitive or "epileptic-like" firing, which could be interpreted as tinnitus by the brain auditory centres.
At first glance, treatment with glutamate antagonists that alter neurotransmission does not seem appropriate to treat hearing loss and tinnitus.
Interestingly, NMDA and metabotropic receptors that appear to be an important component in pathological conditions (i.e, neosynaptogenesis, tinnitus, neuronal death), are those involved to a lesser degree in excitatory synaptic function, making them an attractive therapeutic target.
Another neuropharmacological approach for pathologies linked to glutamate excitotoxicity might also take into account the pharmacology of some lateral efferent agonists.
Numerous neuroactive substances have been found in these synapses: ACh, GABA, dopamine, encephalins, dynorphins, and CGRP (see Eybalin, 1993).
Once again, these molecules, which have limited effects on the normal functioning of the cochlea, are released under pathological conditions such as noise (Drescher et al., 1983 ; Eybalin et al., 1987b, Gil Loyzaga et al., 1993), and could be involved in synaptic plasticity such as the guidance of newly formed dendrites and/or the stabilisation of the IHC synapses (Puel et al., 1995).
Clinical Considerations
What is clear at this point is that there is much work to be done before the above pharmacological speculations can be put into clinical practice.
Future research that relies on molecular information, such as antisense oligonucleotide experiments, knockout strategies, and gene transfer protocols, is still necessary to better understand both physiological and pathological mechanisms underlying synaptic plasticity, control of neuronal excitability, and neuronal death.
Indeed, it is reasonable to assume that subtle molecular mechanisms involved in cochlear function and disease will be more clearly understood in the near future, there are certain restrictions that have to be taken into account for their possible clinical application.
Since the hair cells of the mammalian cochlea do not have the ability to regenerate, we are only left with the hope of finding effective intervention therapies.
A possible concern here is whether, in the therapeutic dose range, these products will cause side effect on the central functions.
Addressing these questions will require the development of a local application of drugs directly into the cochlea.
However, before intervention therapies can be implemented several issues concerning the choice of patients, the route of administration, and the choice of drugs to be applied needs to be determined.
It would be best to reserve in situ cochlear pharmacology for those patients with a normal contralateral ear or with an ear that can easily be fitted with a hearing device.
Decision for the best route of administration will be partially governed by the techniques routinely used in the clinic, and partially by economic soundness.
Two possibilities include an extra-cochlear approach (round or oval window), or, to a direct, intracochlear administration.
The extra-cochlear approach has several disadvantages compared to the intra-cochlear administration. It is most conceivable that the extra-cochlear approach, an invasive operation, will be a one-time procedure.
Taking into the consideration the rapid turnover of perilymph, the therapy drug will be quickly diluted and removed from the perilymph.
As a result of the rapid perilymph turnover, this route of administration may not offer any substantial benefit.
Repeated application would therefore be necessary, but would be unpractical.
It is most likely that cochlear implant patients will have a major role to play in the development of in situ cochlear pharmacology.
The simultaneous implantation of both the cochlear implant electrodes together with a mini-osmotic pump would be possible and the mini-osmotic pump could allow for continuous infusion for weeks.
Even if longer infusion times are required a simple procedure to refill the osmotic pump is all that would be required.
Continued animal experiments are necessary for determining the drug of choice or a combination of drugs as well as their appropriate concentrations. At present, little is known about the long-term effects of drug therapy.
Most animal experiments have ended after either two or four weeks and it is therefore important to gain more information about longer survival times (years) for the morphology and physiology of the hair cells and spiral ganglion neurons.
Conclusions
Our understanding of cochlear protective mechanisms has made significant advances in recent years.
These results have led to new concepts for the homeostasis of the cochlea.
These new concepts consider that the balance of retrograde and anterograde trophic signalling factors determines the overall susceptibility of organ of Corti and spiral ganglion neurons to damage, as schematically shown in [Figure - 3] (Ernfors and Canlon, 1996).
Compromising the organ of Corti will deplete spiral ganglion neurons of neurotrophic support and will eventually result in the death of these cells and disrupting the neurons should deprive hair cells of trophic support causing cell death.
Regardless of the mechanisms of action and whether the effects are direct or not, the fact of the matter is that a giant leap has been made for preventing neuronal and organ of Corti damage and now there are candidate drugs with protective properties for spiral ganglion neurons as well as for cochlear hair cells.
It is conceivable that clinical trials can be performed in the near future and new strategies for preventing hearing loss established.
Acknowledgements
This study was supported by grants from the Swedish Council for Work Life Research (79-0800), Medical Research Council (09476), Stiftelsen Tysta Skolan, and the Karolinska Institute. A joint publication of PAN partners (European Commission BIOMED 2 concerted action - Contract BMH 4-CT96-0110).[66]
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36. Henselman, L.W., Henderson, D., Subramaniam, M., and Sallustio, V. (1994). "The effect of 'conditioning' exposures on hearing loss from impulse noise," Hear. Res. 78, 1-10. Back to cited text no. 36
37. Jacono, A.A., Hu, B., Kopke, R., Henderson, D., Van De Water, T., and Steinman, H.M. (1998) Changes in cochlear antioxidant enzyme activity after sound conditioning and noise exposure in the chinchilla. Hear Res 117, 31-38. Back to cited text no. 37
38. Janssen, R. 1992. Glutamate neurotoxicity in the developing rat cochlea is antagonised by kynurenic acid and MK-801. Brain Res 11, 201-206. Back to cited text no. 38
39. Joachims, Z., Babisch, W., Ising, H., Gunther, T., Handrock, M. (1983) Dependence of noise-induced hearing loss upon perilymph magnesium concentration. J. Acoust. Soc. Am. 74, 104-108. Back to cited text no. 39
40. Juiz J.M., Rueda J., Merchan J.A. and Sala M.L. (1989) The effects of kainic acid on the cochlear ganglion of the rat. Hear. Res. 40, 65-74. Back to cited text no. 40
41. Kujawa, S.G., and Liberman, M.C. (1997). Conditioningrelated protection from acoustic injury: Effects of chronic deefferentation and sham surgery. J. Neurophysiol. 78:3095-3106. Back to cited text no. 41
42. Lautermann, J., Crann, S.A., McLaren, J., and Schacht, J. (1997) Glutathione-dependent antioxidant systems in the mammalian inner ear:effects of aging, ototoxic drugs and noise. Hear Res 114, 75-82. Back to cited text no. 42
43. Lautermann, J., McLaren, J., and Schacht, J. (1995) Glutathione protection against gentamicin ototoxicity depends on nutritional status. Hearing Research. 86(12):15-24. Back to cited text no. 43
44. Lefebvre P.P., Weber T., Leprince P., Rigo J.-M., Delree P., Rogister B., and Moonen G. (1991) Kainate and NMDA toxicity for cultured developing and adult rat spiral ganglion neurons: Further evidence for a glutamatergic excitatory neurotransmission at the inner hair cell synapse. Brain Res. 555, 75-83. Back to cited text no. 44
45. McFadden, S.L., Henderson, D., and Shen, Y.-H. (1997). Low-frequency 'conditioning' provides long-term protection from noise-induced threshold shifts in chinchillas, Hear. Res. 103, 142-150. Back to cited text no. 45
46. Miyakita, T., Hellstrom, P.A., Frimanson, E., and Axelsson, A. (1992) Effect of low level acoustic stimulation on temporary threshold shift in young humans. Hear. Res. 60, 149-155. Back to cited text no. 46
47. Niedzielski, A. S. and Wenthold, R. J. (1995). Expression of AMPA, kainate, and NMDA receptor subunits in cochlear and vestibular ganglia. J. Neurosci. 15, 2338-2353. Back to cited text no. 47
48. Ohlsen, K. A., Didier, A., Baldwin, D., Miller, J. M., Nuttall, A. L., and Hultcrantz, E. (1992) Cochlear blood flow in response to dilating agents. Hearing Research. 58(1):19-25. Back to cited text no. 48
49. Puel J.L, Pujol R, Tribillac F, Ladrech S, Eybalin M:(1994) Excitatory amino acid antagonists protect cochlear auditory neurons from excitotoxicity. J Comp Neurol 341, 241-256. Back to cited text no. 49
50. Puel J.L., Safieddine S. , Gervais d'Aldin C., Eybalin M. and Pujol R. (1995) Synaptic regeneration and functional recovery after excitotoxic injury in the cochlea. C.R. Acad. Sci., Serie III, 318, 67-75. Back to cited text no. 50
51. Puel, J.-L, D'Aldin C., Safieddine S., Eybalin M. et Pujol R (1996). Excitotoxicity and plasticity of the IHC-auditory nerve synapse contribute to both TTS and PTS. In: Scientific Basis of Noise Induced Hearing Loss, A. Axelsson, R.P. Hamernik et R.J. Salvi (eds), Thieme Medical Publishers, INC., New York, , pp.36-42. Back to cited text no. 51
52. Puel J-L., Puel J., d'Aldin C. and Pujol R. (1998) Excitotoxicity and repair of cochlear synapses after noisetrauma induced hearing loss. NeuroReport 9, in press Back to cited text no. 52
53. Puel, J-L., Ladrech, S., Chabert, R., Pujol, R., and Eybalin, M. (1991) Electrophysiological evidence for the presence of NMDA receptors in the guinea pig cochlea. Hear Res 51, 255-264. Back to cited text no. 53
54. Pujol R., Puel J-L., Gervais d'Aldin C., Eybalin M. (1993) Pathophysiology of the glutamatergic synapses in the cochlea. Acta Otolaryngol 113, 330-334. Back to cited text no. 54
55. Pujol R., Rebillard G., Puel J.-L., Lenoir M., Eybalin M. et Recasens M. (1990) Glutamate neurotoxicity in the cochlea : a possible consequence of ischaemic or anoxic conditions occurring in aging. Acta Otolaryngol. (Stockh.), suppl. 476, 32-36. Back to cited text no. 55
56. Pukkila, M., Zhai, S., Virkkala, J., Pirovola, U., and Ylikoski, J. (1997) The "toughening" phenomenon in rat´s auditory organ. Acta Otolaryngol. 529:59-62. Back to cited text no. 56
57. Quirk W.S., Shivapuja B.G., Schwimmer C.L., Seidman M..D. (1994) Lipid peroxidation inhibitor attenuates noise-induced temporary threshold shifts. Hear Res 74, 217-220. Back to cited text no. 57
58. Rarey, K.E., Gerhardt, K.J., Curtis, L.M., and ten Cate, W.J-F. (1995) Effect of stress on cochlear glucocorticoid protein: acoustic stress. Hear. Res. 82: 135-138. Back to cited text no. 58
59. Robertson, D. (1983) Functional significance of dendritic swelling after loud sounds in the guinea pig cochlea. Hear. Res. 9, 263-278. Back to cited text no. 59
60. Ryan, A.F., Bennett, T.M., Woolf, N.K., and Axelsson, A. (1994). Protection from noise-induced hearing loss by prior exposure to a nontraumatic stimulus: Role of the middle ear muscles, Hear. Res. 72, 23-28. Back to cited text no. 60
61. Seidman, M.D., Shivapuja, B.G., and Quirk, W.S. (1993) The protective effects of allopurinol and superoxide dismutase on noise-induced cochlear damage. Otolaryngol. Head Neck Surg. 109, 1052-1056. Back to cited text no. 61
62. Sinex, D.G., Clark, W.W., and Bohne, B.A. (1987). Effect of periodic rest on physiological measures of auditory sensitivity following exposure to noise, J. Acoust. Soc. Am. 82, 1265-1273. Back to cited text no. 62
63. Spoendlin, H. (1971) Primary structural changes in the organ of Corti after acoustic overstimulation. Acta Otolaryngol (Stockh). 71, 166-176. Subramaniam, M., Campo, P., and Henderson, D. (1991) The effect of exposure level on the development of progressive resistance to noise. Hear. Res. 52, 181-188. Back to cited text no. 63
64. White DR, Boettcher FA, Miles LR, Gratton MA (1998) Effectiveness of intermittent and continuous acoustic stimulation in preventing noise-induced hearing and hair cell loss. J. Acoust Soc Am 103(3):1566-1572. Back to cited text no. 64
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Fuente: http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=1998;volume=1;issue=1;spage=13;epage=23;aulast=Canlon
Audición: seccción fisiopatología, el rol protector de los glucocorticoides
Protección del sistema auditivo con glucocorticoides
Bárbara Canlon
un Eulers von vag 8
Stockholm Suecia
Barbara Canlon, Audiophysiology, Karolinska instituet.
abstracto
Los glucocorticoides son hormonas que se liberan después de episodios relacionados con estrés y su función es la de mantener la homeostasis.
Los receptores de glucocorticoides, se localizan entre otras partes en las células ciliadas, ligamento espiral y las neuronas del ganglio espiral.
La protección del receptor de glucocorticoides contra daño inducido por trauma acústico se encuentra en: I) antes del tratamiento con agonistas de glucocorticoides, ll) la retención de la tensión aguda, y ll) en el acondicionamiento sonoro.
Por el contrario, los antagonistas del receptor de glucocorticoides exacerban la pérdida de audición.
Estos hallazgos tienen relevancia clínica importante, ya que los glucocorticoides sintéticos se utilizan comúnmente para tratar la pérdida de la audición.
Sin embargo, este tratamiento tiene un éxito limitado, ya que si bien mejoran la audición a menudo no mantienen esta mejoría una vez finalizado el tratamiento, lo que reduce el atractivo general para este tratamiento.
Debe tenerse en cuenta que a pesar del uso extendido de estos fármacos para tratar trastornos de la audición, los mecanismos moleculares que subyacen a este tratamiento no están bien caracterizados.
En esta revisión se dan una idea de algunos de los mecanismos fisiológicos y bioquímicos subyacentes a tratamiento con glucocorticoides para prevenir la pérdida de la audición
Palabras clave: Trauma acústico, la audición, pérdida de la audición, la cóclea, el eje HPA, la corticosterona, la protección
fuente: ScienceDirect.com
Bárbara Canlon
un Eulers von vag 8
Stockholm Suecia
Barbara Canlon, Audiophysiology, Karolinska instituet.
abstracto
Los glucocorticoides son hormonas que se liberan después de episodios relacionados con estrés y su función es la de mantener la homeostasis.
Los receptores de glucocorticoides, se localizan entre otras partes en las células ciliadas, ligamento espiral y las neuronas del ganglio espiral.
La protección del receptor de glucocorticoides contra daño inducido por trauma acústico se encuentra en: I) antes del tratamiento con agonistas de glucocorticoides, ll) la retención de la tensión aguda, y ll) en el acondicionamiento sonoro.
Por el contrario, los antagonistas del receptor de glucocorticoides exacerban la pérdida de audición.
Estos hallazgos tienen relevancia clínica importante, ya que los glucocorticoides sintéticos se utilizan comúnmente para tratar la pérdida de la audición.
Sin embargo, este tratamiento tiene un éxito limitado, ya que si bien mejoran la audición a menudo no mantienen esta mejoría una vez finalizado el tratamiento, lo que reduce el atractivo general para este tratamiento.
Debe tenerse en cuenta que a pesar del uso extendido de estos fármacos para tratar trastornos de la audición, los mecanismos moleculares que subyacen a este tratamiento no están bien caracterizados.
En esta revisión se dan una idea de algunos de los mecanismos fisiológicos y bioquímicos subyacentes a tratamiento con glucocorticoides para prevenir la pérdida de la audición
Palabras clave: Trauma acústico, la audición, pérdida de la audición, la cóclea, el eje HPA, la corticosterona, la protección
fuente: ScienceDirect.com
domingo, 19 de junio de 2011
Hipoacusia: Genes involucrados en la perdida de la audición: DFNA40
DFNA40 - deafness, autosomal dominant 40
Homo sapiens
fuente de la imagen: prensalibreonline.com.ar
Autores
Birkenhäger, R. et al., Schönberger, J. et al., Bespalova, I.N. et al., Yueh, B. et al., Dodge, P.R. et al., et al.
Kelsell, Dunlop, Stevens, Lench, Liang, Parry, Mueller, Leigh, Gopal, Yueh, Shapiro, MacLean, Shekelle, Chiang, Roden, Copeland, Pillsbury,
Disease relevance of DFNA40
• Transient conductive hearing impairment was found in 16 per cent of the sample, but in no case was there apparent improvement in a sensorineural deficit over time [1].
• Thiamine-responsive megaloblastic anaemia syndrome (TRMA; MIM 249270) is an autosomal recessive disorder with features that include megaloblastic anaemia, mild thrombocytopenia and leucopenia, sensorineural deafness and diabetes mellitus [2].
• Thus, our results suggest that mutations in MYH9 result in three megakaryocyte/platelet/leukocyte syndromes and are important in the pathogenesis of sensorineural deafness, cataracts and nephritis [3].
• Usher syndrome type 1 (USH1) is an autosomal recessive sensory defect involving congenital profound sensorineural deafness, vestibular dysfunction and blindness (due to progressive retinitis pigmentosa)1 [4].
• Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure [5].
Psychiatry related information on DFNA40
• Only 14 children (14 percent) had persisting neurologic sequelae: sensorineural hearing loss in 11 (unilateral in 6 and bilateral in 5), seizure disorder in 2, and hemiplegia and mental retardation in 1 [6].
• MELAS is a mitochondrial encephalomyopathy characterized clinically by recurrent stroke-like episodes, seizures, sensorineural deafness, dementia, hypertrophic cardiomyopathy, and short stature [7].
• Progressive optic atrophy and sensorineural hearing loss due to chronic glue sniffing [8].
• Mercury is known to cause sensorineural hearing loss and impaired speech perception [9].
• Auditory stimulus intensity and reaction time in listeners with longstanding sensorineural hearing loss [10].
High impact information on DFNA40
• Unlike previously described sensorineural deafness genes, all of which underlie cochlear cell pathologies, DFNB59 is the first human gene implicated in nonsyndromic deafness due to a neuronal defect [11].
• Mutation in the transcriptional coactivator EYA4 causes dilated cardiomyopathy and sensorineural hearing loss [12].
• We find that the affected individuals of two families also presented with progressive sensorineural high-frequency hearing loss (gene DFNA39) [13].
• Additional aspects of the phenotype include sensorineural deafness, reduced lifespan and decreased reproductive fitness [14].
• We have identified two frameshift mutations and a large deletion in the copy containing 29 coding exons in two families affected by autosomal recessive non-syndromal sensorineural deafness linked to the DFNB16 locus [15].
Chemical compound and disease context of DFNA40
• Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270) [16].
• Patients with a nonsense mutation in CD151 display end-stage kidney failure associated with regional skin blistering and sensorineural deafness, and mice lacking the integrin alpha3 subunit die neonatally because of severe abnormalities in the lung and kidney epithelia [17].
• The objective of this study was to determine whether a mitochondrial DNA mutation and defective oxidative phosphorylation are present in a pedigree with maternally inherited sensorineural deafness, levodopa-responsive parkinsonism, and neuropathy [18].
• Pendred's syndrome is an autosomal recessive disorder characterized by sensorineural deafness, goiter, and impaired iodide organification [19].
• The affected subject was a 22-yr-old man with a history of myoclonic epilepsy and mild sensorineural hearing loss, a 1-yr duration of diabetes mellitus, and a low level C peptide response to oral glucose [20].
Biological context of DFNA40
• Using positional information from a patient with a 21-kb deletion in chromosome Xq22 and sensorineural deafness along with dystonia, we characterized a novel transcript lying within the deletion as a candidate for this complex syndrome [21].
• Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2 [22].
• DFNB3, a locus for nonsyndromic sensorineural recessive deafness, maps to a 3-centimorgan interval on human chromosome 17p11.2, a region that shows conserved synteny with mouse shaker-2 [23].
• Blood viscosity as a factor in sensorineural hearing impairment [24].
• Ablation or missense mutations of the pump cause deafness, as described for the G283S mutation in the deafwaddler (dfw) mouse [25].
Anatomical context of DFNA40
• Our findings revealed a unique ultrastructural malformation of inner-ear architecture associated with non-syndromic hearing loss, and suggest that tectorial membrane abnormalities may be one aetiology of sensorineural hearing loss primarily affecting the mid-frequencies [26].
• Patients with ATP6B1 mutations also have sensorineural hearing loss; consistent with this finding, we demonstrate expression of ATP6B1 in cochlea and endolymphatic sac [27].
• Pendred syndrome is an autosomal recessive disorder associated with developmental abnormalities of the cochlea, sensorineural hearing loss and diffuse thyroid enlargement (goitre) [28].
• To our knowledge, this is the first non-syndromic sensorineural autosomal deafness susceptibility gene to be identified, which implicates Cx26 as an important component of the human cochlea [29].
• Screening is endorsed by most professional organizations, including the US Preventive Services Task Force. While most hearing loss in older adults is sensorineural and due to presbycusis, cerumen impaction and chronic otitis media may be present in up to 30% of elderly patients with hearing loss and can be treated by the primary care clinician [30].
Associations of DFNA40 with chemical compounds
• As compared with those who received placebo, the patients who received dexamethasone became afebrile earlier (1.6 vs. 5.0 days; P less than 0.001) and were less likely to acquire moderate or more severe bilateral sensorineural hearing loss (15.5 vs. 3.3 percent; P less than 0.01) [31].
• Pharmacological doses of thiamine correct the anaemia, and in some cases improve the diabetes, although progressive sensorineural deafness is irreversible [32].
• Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit [33].
• Mutations in the Wolfram syndrome 1 gene (WFS1) are a common cause of low frequency sensorineural hearing loss [34].
• Steroid-responsive postinfectious sensorineural hearing loss [35].
Physical interactions of DFNA40
• Otosclerosis is a disease of complex unknown etiology causing progressive conductive and/or sensorineural hearing loss (HL) [36].
Other interactions of DFNA40
• We report here a dominant mutation in the GJB3 gene (D66del) in a family affected with peripheral neuropathy and sensorineural hearing impairment [37].
• Mutations in SOX10, a transcription modulator crucial in the development of the enteric nervous system (ENS), melanocytes and glial cells, are found in Shah-Waardenburg syndrome (WS4), a neurocristopathy that associates intestinal aganglionosis, pigmentation defects and sensorineural deafness [38].
• The much rarer Jervell-Lange-Nielsen syndrome (with marked QT prolongation and sensorineural deafness) arises when a child inherits mutant KVLQT1 or minK alleles from both parents [39].
• A gene for an autosomal dominant form of progressive sensorineural hearing loss (DFNA5) was previously assigned by us to a 15-cM region on chromosome 7p15 [40].
• Defects in the human gene encoding DSPP cause inherited dentin defects, and these defects can be associated with bilateral progressive high-frequency sensorineural hearing loss [41].
Analytical, diagnostic and therapeutic context of DFNA40
• The hearing loss was characterized by a high-frequency sensorineural deficit, which necessitated hearing aids in six patients [42].
• The number of days of illness (symptoms) before hospitalization and institution of antibacterial treatment was not correlated with the development of sensorineural deafness [1].
• Correlation between antibodies to type II collagen and treatment outcome in bilateral progressive sensorineural hearing loss [43].
• On pure-tone audiometry, 19 patients were shown to have sensorineural hearing loss, 3 of whom had evidence of an added conductive element [44].
• Cochlear implants have dramatically changed the treatment and prognosis for patients with profound sensorineural hearing loss [45].
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25. A functional study of plasma-membrane calcium-pump isoform 2 mutants causing digenic deafness. Ficarella, R., Di Leva, F., Bortolozzi, M., Ortolano, S., Donaudy, F., Petrillo, M., Melchionda, S., Lelli, A., Domi, T., Fedrizzi, L., Lim, D., Shull, G.E., Gasparini, P., Brini, M., Mammano, F., Carafoli, E. Proc. Natl. Acad. Sci. U.S.A. (2007)
26. Mutations in COL11A2 cause non-syndromic hearing loss (DFNA13). McGuirt, W.T., Prasad, S.D., Griffith, A.J., Kunst, H.P., Green, G.E., Shpargel, K.B., Runge, C., Huybrechts, C., Mueller, R.F., Lynch, E., King, M.C., Brunner, H.G., Cremers, C.W., Takanosu, M., Li, S.W., Arita, M., Mayne, R., Prockop, D.J., Van Camp, G., Smith, R.J. Nat. Genet. (1999)
27. Mutations in the gene encoding B1 subunit of H+-ATPase cause renal tubular acidosis with sensorineural deafness. Karet, F.E., Finberg, K.E., Nelson, R.D., Nayir, A., Mocan, H., Sanjad, S.A., Rodriguez-Soriano, J., Santos, F., Cremers, C.W., Di Pietro, A., Hoffbrand, B.I., Winiarski, J., Bakkaloglu, A., Ozen, S., Dusunsel, R., Goodyer, P., Hulton, S.A., Wu, D.K., Skvorak, A.B., Morton, C.C., Cunningham, M.J., Jha, V., Lifton, R.P. Nat. Genet. (1999)
28. Pendred syndrome (goitre and sensorineural hearing loss) maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4. Coyle, B., Coffey, R., Armour, J.A., Gausden, E., Hochberg, Z., Grossman, A., Britton, K., Pembrey, M., Reardon, W., Trembath, R. Nat. Genet. (1996)
29. Connexin 26 mutations in hereditary non-syndromic sensorineural deafness. Kelsell, D.P., Dunlop, J., Stevens, H.P., Lench, N.J., Liang, J.N., Parry, G., Mueller, R.F., Leigh, I.M. Nature (1997)
30. Screening and management of adult hearing loss in primary care: scientific review. Yueh, B., Shapiro, N., MacLean, C.H., Shekelle, P.G. JAMA (2003)
31. Dexamethasone therapy for bacterial meningitis. Results of two double-blind, placebo-controlled trials. Lebel, M.H., Freij, B.J., Syrogiannopoulos, G.A., Chrane, D.F., Hoyt, M.J., Stewart, S.M., Kennard, B.D., Olsen, K.D., McCracken, G.H. N. Engl. J. Med. (1988)
32. The gene mutated in thiamine-responsive anaemia with diabetes and deafness (TRMA) encodes a functional thiamine transporter. Fleming, J.C., Tartaglini, E., Steinkamp, M.P., Schorderet, D.F., Cohen, N., Neufeld, E.J. Nat. Genet. (1999)
33. Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes. Annunen, S., Körkkö, J., Czarny, M., Warman, M.L., Brunner, H.G., Kääriäinen, H., Mulliken, J.B., Tranebjaerg, L., Brooks, D.G., Cox, G.F., Cruysberg, J.R., Curtis, M.A., Davenport, S.L., Friedrich, C.A., Kaitila, I., Krawczynski, M.R., Latos-Bielenska, A., Mukai, S., Olsen, B.R., Shinno, N., Somer, M., Vikkula, M., Zlotogora, J., Prockop, D.J., Ala-Kokko, L. Am. J. Hum. Genet. (1999)
34. Mutations in the Wolfram syndrome 1 gene (WFS1) are a common cause of low frequency sensorineural hearing loss. Bespalova, I.N., Van Camp, G., Bom, S.J., Brown, D.J., Cryns, K., DeWan, A.T., Erson, A.E., Flothmann, K., Kunst, H.P., Kurnool, P., Sivakumaran, T.A., Cremers, C.W., Leal, S.M., Burmeister, M., Lesperance, M.M. Hum. Mol. Genet. (2001)
35. Steroid-responsive postinfectious sensorineural hearing loss. Amir, N., Shalev, R.S., Berman, M., Gilai, A., Mor, J. Ann. Neurol. (1984)
36. Antimeasles immunoglobulin g for serologic diagnosis of otosclerotic hearing loss. Karosi, T., Kónya, J., Petkó, M., Szabó, L.Z., Pytel, J., Jóri, J., Sziklai, I. Laryngoscope (2006)
37. Connexin 31 (GJB3) is expressed in the peripheral and auditory nerves and causes neuropathy and hearing impairment. López-Bigas, N., Olivé, M., Rabionet, R., Ben-David, O., Martínez-Matos, J.A., Bravo, O., Banchs, I., Volpini, V., Gasparini, P., Avraham, K.B., Ferrer, I., Arbonés, M.L., Estivill, X. Hum. Mol. Genet. (2001)
38. Human Connexin 32, a gap junction protein altered in the X-linked form of Charcot-Marie-Tooth disease, is directly regulated by the transcription factor SOX10. Bondurand, N., Girard, M., Pingault, V., Lemort, N., Dubourg, O., Goossens, M. Hum. Mol. Genet. (2001)
39. The long QT syndromes: genetic basis and clinical implications. Chiang, C.E., Roden, D.M. J. Am. Coll. Cardiol. (2000)
40. Refined mapping of a gene for autosomal dominant progressive sensorineural hearing loss (DFNA5) to a 2-cM region, and exclusion of a candidate gene that is expressed in the cochlea. Van Laer, L., Van Camp, G., van Zuijlen, D., Green, E.D., Verstreken, M., Schatteman, I., Van de Heyning, P., Balemans, W., Coucke, P., Greinwald, J.H., Smith, R.J., Huizing, E., Willems, P. Eur. J. Hum. Genet. (1997)
41. A novel splice acceptor mutation in the DSPP gene causing dentinogenesis imperfecta type II. Kim, J.W., Nam, S.H., Jang, K.T., Lee, S.H., Kim, C.C., Hahn, S.H., Hu, J.C., Simmer, J.P. Hum. Genet. (2004)
42. Visual and auditory neurotoxicity in patients receiving subcutaneous deferoxamine infusions. Olivieri, N.F., Buncic, J.R., Chew, E., Gallant, T., Harrison, R.V., Keenan, N., Logan, W., Mitchell, D., Ricci, G., Skarf, B. N. Engl. J. Med. (1986)
43. Correlation between antibodies to type II collagen and treatment outcome in bilateral progressive sensorineural hearing loss. Helfgott, S.M., Mosciscki, R.A., San Martin, J., Lorenzo, C., Kieval, R., McKenna, M., Nadol, J., Trentham, D.E. Lancet (1991)
44. Impaired hearing in X-linked hypophosphataemic (vitamin-D-resistant) osteomalacia. Davies, M., Kane, R., Valentine, J. Ann. Intern. Med. (1984)
45. Cochlear implantation for the treatment of deafness. Copeland, B.J., Pillsbury, H.C. Annu. Rev. Med. (2004)
fuente: http://www.wikigenes.org/e/gene/e/63945.html
Homo sapiens
fuente de la imagen: prensalibreonline.com.ar
Autores
Birkenhäger, R. et al., Schönberger, J. et al., Bespalova, I.N. et al., Yueh, B. et al., Dodge, P.R. et al., et al.
Kelsell, Dunlop, Stevens, Lench, Liang, Parry, Mueller, Leigh, Gopal, Yueh, Shapiro, MacLean, Shekelle, Chiang, Roden, Copeland, Pillsbury,
Disease relevance of DFNA40
• Transient conductive hearing impairment was found in 16 per cent of the sample, but in no case was there apparent improvement in a sensorineural deficit over time [1].
• Thiamine-responsive megaloblastic anaemia syndrome (TRMA; MIM 249270) is an autosomal recessive disorder with features that include megaloblastic anaemia, mild thrombocytopenia and leucopenia, sensorineural deafness and diabetes mellitus [2].
• Thus, our results suggest that mutations in MYH9 result in three megakaryocyte/platelet/leukocyte syndromes and are important in the pathogenesis of sensorineural deafness, cataracts and nephritis [3].
• Usher syndrome type 1 (USH1) is an autosomal recessive sensory defect involving congenital profound sensorineural deafness, vestibular dysfunction and blindness (due to progressive retinitis pigmentosa)1 [4].
• Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure [5].
Psychiatry related information on DFNA40
• Only 14 children (14 percent) had persisting neurologic sequelae: sensorineural hearing loss in 11 (unilateral in 6 and bilateral in 5), seizure disorder in 2, and hemiplegia and mental retardation in 1 [6].
• MELAS is a mitochondrial encephalomyopathy characterized clinically by recurrent stroke-like episodes, seizures, sensorineural deafness, dementia, hypertrophic cardiomyopathy, and short stature [7].
• Progressive optic atrophy and sensorineural hearing loss due to chronic glue sniffing [8].
• Mercury is known to cause sensorineural hearing loss and impaired speech perception [9].
• Auditory stimulus intensity and reaction time in listeners with longstanding sensorineural hearing loss [10].
High impact information on DFNA40
• Unlike previously described sensorineural deafness genes, all of which underlie cochlear cell pathologies, DFNB59 is the first human gene implicated in nonsyndromic deafness due to a neuronal defect [11].
• Mutation in the transcriptional coactivator EYA4 causes dilated cardiomyopathy and sensorineural hearing loss [12].
• We find that the affected individuals of two families also presented with progressive sensorineural high-frequency hearing loss (gene DFNA39) [13].
• Additional aspects of the phenotype include sensorineural deafness, reduced lifespan and decreased reproductive fitness [14].
• We have identified two frameshift mutations and a large deletion in the copy containing 29 coding exons in two families affected by autosomal recessive non-syndromal sensorineural deafness linked to the DFNB16 locus [15].
Chemical compound and disease context of DFNA40
• Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270) [16].
• Patients with a nonsense mutation in CD151 display end-stage kidney failure associated with regional skin blistering and sensorineural deafness, and mice lacking the integrin alpha3 subunit die neonatally because of severe abnormalities in the lung and kidney epithelia [17].
• The objective of this study was to determine whether a mitochondrial DNA mutation and defective oxidative phosphorylation are present in a pedigree with maternally inherited sensorineural deafness, levodopa-responsive parkinsonism, and neuropathy [18].
• Pendred's syndrome is an autosomal recessive disorder characterized by sensorineural deafness, goiter, and impaired iodide organification [19].
• The affected subject was a 22-yr-old man with a history of myoclonic epilepsy and mild sensorineural hearing loss, a 1-yr duration of diabetes mellitus, and a low level C peptide response to oral glucose [20].
Biological context of DFNA40
• Using positional information from a patient with a 21-kb deletion in chromosome Xq22 and sensorineural deafness along with dystonia, we characterized a novel transcript lying within the deletion as a candidate for this complex syndrome [21].
• Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2 [22].
• DFNB3, a locus for nonsyndromic sensorineural recessive deafness, maps to a 3-centimorgan interval on human chromosome 17p11.2, a region that shows conserved synteny with mouse shaker-2 [23].
• Blood viscosity as a factor in sensorineural hearing impairment [24].
• Ablation or missense mutations of the pump cause deafness, as described for the G283S mutation in the deafwaddler (dfw) mouse [25].
Anatomical context of DFNA40
• Our findings revealed a unique ultrastructural malformation of inner-ear architecture associated with non-syndromic hearing loss, and suggest that tectorial membrane abnormalities may be one aetiology of sensorineural hearing loss primarily affecting the mid-frequencies [26].
• Patients with ATP6B1 mutations also have sensorineural hearing loss; consistent with this finding, we demonstrate expression of ATP6B1 in cochlea and endolymphatic sac [27].
• Pendred syndrome is an autosomal recessive disorder associated with developmental abnormalities of the cochlea, sensorineural hearing loss and diffuse thyroid enlargement (goitre) [28].
• To our knowledge, this is the first non-syndromic sensorineural autosomal deafness susceptibility gene to be identified, which implicates Cx26 as an important component of the human cochlea [29].
• Screening is endorsed by most professional organizations, including the US Preventive Services Task Force. While most hearing loss in older adults is sensorineural and due to presbycusis, cerumen impaction and chronic otitis media may be present in up to 30% of elderly patients with hearing loss and can be treated by the primary care clinician [30].
Associations of DFNA40 with chemical compounds
• As compared with those who received placebo, the patients who received dexamethasone became afebrile earlier (1.6 vs. 5.0 days; P less than 0.001) and were less likely to acquire moderate or more severe bilateral sensorineural hearing loss (15.5 vs. 3.3 percent; P less than 0.01) [31].
• Pharmacological doses of thiamine correct the anaemia, and in some cases improve the diabetes, although progressive sensorineural deafness is irreversible [32].
• Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit [33].
• Mutations in the Wolfram syndrome 1 gene (WFS1) are a common cause of low frequency sensorineural hearing loss [34].
• Steroid-responsive postinfectious sensorineural hearing loss [35].
Physical interactions of DFNA40
• Otosclerosis is a disease of complex unknown etiology causing progressive conductive and/or sensorineural hearing loss (HL) [36].
Other interactions of DFNA40
• We report here a dominant mutation in the GJB3 gene (D66del) in a family affected with peripheral neuropathy and sensorineural hearing impairment [37].
• Mutations in SOX10, a transcription modulator crucial in the development of the enteric nervous system (ENS), melanocytes and glial cells, are found in Shah-Waardenburg syndrome (WS4), a neurocristopathy that associates intestinal aganglionosis, pigmentation defects and sensorineural deafness [38].
• The much rarer Jervell-Lange-Nielsen syndrome (with marked QT prolongation and sensorineural deafness) arises when a child inherits mutant KVLQT1 or minK alleles from both parents [39].
• A gene for an autosomal dominant form of progressive sensorineural hearing loss (DFNA5) was previously assigned by us to a 15-cM region on chromosome 7p15 [40].
• Defects in the human gene encoding DSPP cause inherited dentin defects, and these defects can be associated with bilateral progressive high-frequency sensorineural hearing loss [41].
Analytical, diagnostic and therapeutic context of DFNA40
• The hearing loss was characterized by a high-frequency sensorineural deficit, which necessitated hearing aids in six patients [42].
• The number of days of illness (symptoms) before hospitalization and institution of antibacterial treatment was not correlated with the development of sensorineural deafness [1].
• Correlation between antibodies to type II collagen and treatment outcome in bilateral progressive sensorineural hearing loss [43].
• On pure-tone audiometry, 19 patients were shown to have sensorineural hearing loss, 3 of whom had evidence of an added conductive element [44].
• Cochlear implants have dramatically changed the treatment and prognosis for patients with profound sensorineural hearing loss [45].
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11. Mutations in the gene encoding pejvakin, a newly identified protein of the afferent auditory pathway, cause DFNB59 auditory neuropathy. Delmaghani, S., del Castillo, F.J., Michel, V., Leibovici, M., Aghaie, A., Ron, U., Van Laer, L., Ben-Tal, N., Van Camp, G., Weil, D., Langa, F., Lathrop, M., Avan, P., Petit, C. Nat. Genet. (2006)
12. Mutation in the transcriptional coactivator EYA4 causes dilated cardiomyopathy and sensorineural hearing loss. Schönberger, J., Wang, L., Shin, J.T., Kim, S.D., Depreux, F.F., Zhu, H., Zon, L., Pizard, A., Kim, J.B., Macrae, C.A., Mungall, A.J., Seidman, J.G., Seidman, C.E. Nat. Genet. (2005)
13. Dentinogenesis imperfecta 1 with or without progressive hearing loss is associated with distinct mutations in DSPP. Xiao, S., Yu, C., Chou, X., Yuan, W., Wang, Y., Bu, L., Fu, G., Qian, M., Yang, J., Shi, Y., Hu, L., Han, B., Wang, Z., Huang, W., Liu, J., Chen, Z., Zhao, G., Kong, X. Nat. Genet. (2001)
14. Mutant glycosyltransferase and altered glycosylation of alpha-dystroglycan in the myodystrophy mouse. Grewal, P.K., Holzfeind, P.J., Bittner, R.E., Hewitt, J.E. Nat. Genet. (2001)
15. Mutations in a new gene encoding a protein of the hair bundle cause non-syndromic deafness at the DFNB16 locus. Verpy, E., Masmoudi, S., Zwaenepoel, I., Leibovici, M., Hutchin, T.P., Del Castillo, I., Nouaille, S., Blanchard, S., Lainé, S., Popot, J.L., Moreno, F., Mueller, R.F., Petit, C. Nat. Genet. (2001)
16. Mutations in SLC19A2 cause thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and deafness. Labay, V., Raz, T., Baron, D., Mandel, H., Williams, H., Barrett, T., Szargel, R., McDonald, L., Shalata, A., Nosaka, K., Gregory, S., Cohen, N. Nat. Genet. (1999)
17. Kidney failure in mice lacking the tetraspanin CD151. Sachs, N., Kreft, M., van den Bergh Weerman, M.A., Beynon, A.J., Peters, T.A., Weening, J.J., Sonnenberg, A. J. Cell Biol. (2006)
18. A novel mitochondrial 12SrRNA point mutation in parkinsonism, deafness, and neuropathy. Thyagarajan, D., Bressman, S., Bruno, C., Przedborski, S., Shanske, S., Lynch, T., Fahn, S., DiMauro, S. Ann. Neurol. (2000)
19. Functional characterization of pendrin in a polarized cell system. Evidence for pendrin-mediated apical iodide efflux. Gillam, M.P., Sidhaye, A.R., Lee, E.J., Rutishauser, J., Stephan, C.W., Kopp, P. J. Biol. Chem. (2004)
20. Mitochondrial gene transfer ribonucleic acid (tRNA)Leu(UUR) 3243 and tRNA(Lys) 8344 mutations and diabetes mellitus in Korea. Lee, H.C., Song, Y.D., Li, H.R., Park, J.O., Suh, H.C., Lee, E., Lim, S., Kim, K., Huh, K. J. Clin. Endocrinol. Metab. (1997)
21. A novel X-linked gene, DDP, shows mutations in families with deafness (DFN-1), dystonia, mental deficiency and blindness. Jin, H., May, M., Tranebjaerg, L., Kendall, E., Fontán, G., Jackson, J., Subramony, S.H., Arena, F., Lubs, H., Smith, S., Stevenson, R., Schwartz, C., Vetrie, D. Nat. Genet. (1996)
22. Mutation of a gene encoding a protein with extracellular matrix motifs in Usher syndrome type IIa. Eudy, J.D., Weston, M.D., Yao, S., Hoover, D.M., Rehm, H.L., Ma-Edmonds, M., Yan, D., Ahmad, I., Cheng, J.J., Ayuso, C., Cremers, C., Davenport, S., Moller, C., Talmadge, C.B., Beisel, K.W., Tamayo, M., Morton, C.C., Swaroop, A., Kimberling, W.J., Sumegi, J. Science (1998)
23. Association of unconventional myosin MYO15 mutations with human nonsyndromic deafness DFNB3. Wang, A., Liang, Y., Fridell, R.A., Probst, F.J., Wilcox, E.R., Touchman, J.W., Morton, C.C., Morell, R.J., Noben-Trauth, K., Camper, S.A., Friedman, T.B. Science (1998)
24. Blood viscosity as a factor in sensorineural hearing impairment. Browning, G.G., Gatehouse, S., Lowe, G.D. Lancet (1986)
25. A functional study of plasma-membrane calcium-pump isoform 2 mutants causing digenic deafness. Ficarella, R., Di Leva, F., Bortolozzi, M., Ortolano, S., Donaudy, F., Petrillo, M., Melchionda, S., Lelli, A., Domi, T., Fedrizzi, L., Lim, D., Shull, G.E., Gasparini, P., Brini, M., Mammano, F., Carafoli, E. Proc. Natl. Acad. Sci. U.S.A. (2007)
26. Mutations in COL11A2 cause non-syndromic hearing loss (DFNA13). McGuirt, W.T., Prasad, S.D., Griffith, A.J., Kunst, H.P., Green, G.E., Shpargel, K.B., Runge, C., Huybrechts, C., Mueller, R.F., Lynch, E., King, M.C., Brunner, H.G., Cremers, C.W., Takanosu, M., Li, S.W., Arita, M., Mayne, R., Prockop, D.J., Van Camp, G., Smith, R.J. Nat. Genet. (1999)
27. Mutations in the gene encoding B1 subunit of H+-ATPase cause renal tubular acidosis with sensorineural deafness. Karet, F.E., Finberg, K.E., Nelson, R.D., Nayir, A., Mocan, H., Sanjad, S.A., Rodriguez-Soriano, J., Santos, F., Cremers, C.W., Di Pietro, A., Hoffbrand, B.I., Winiarski, J., Bakkaloglu, A., Ozen, S., Dusunsel, R., Goodyer, P., Hulton, S.A., Wu, D.K., Skvorak, A.B., Morton, C.C., Cunningham, M.J., Jha, V., Lifton, R.P. Nat. Genet. (1999)
28. Pendred syndrome (goitre and sensorineural hearing loss) maps to chromosome 7 in the region containing the nonsyndromic deafness gene DFNB4. Coyle, B., Coffey, R., Armour, J.A., Gausden, E., Hochberg, Z., Grossman, A., Britton, K., Pembrey, M., Reardon, W., Trembath, R. Nat. Genet. (1996)
29. Connexin 26 mutations in hereditary non-syndromic sensorineural deafness. Kelsell, D.P., Dunlop, J., Stevens, H.P., Lench, N.J., Liang, J.N., Parry, G., Mueller, R.F., Leigh, I.M. Nature (1997)
30. Screening and management of adult hearing loss in primary care: scientific review. Yueh, B., Shapiro, N., MacLean, C.H., Shekelle, P.G. JAMA (2003)
31. Dexamethasone therapy for bacterial meningitis. Results of two double-blind, placebo-controlled trials. Lebel, M.H., Freij, B.J., Syrogiannopoulos, G.A., Chrane, D.F., Hoyt, M.J., Stewart, S.M., Kennard, B.D., Olsen, K.D., McCracken, G.H. N. Engl. J. Med. (1988)
32. The gene mutated in thiamine-responsive anaemia with diabetes and deafness (TRMA) encodes a functional thiamine transporter. Fleming, J.C., Tartaglini, E., Steinkamp, M.P., Schorderet, D.F., Cohen, N., Neufeld, E.J. Nat. Genet. (1999)
33. Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes. Annunen, S., Körkkö, J., Czarny, M., Warman, M.L., Brunner, H.G., Kääriäinen, H., Mulliken, J.B., Tranebjaerg, L., Brooks, D.G., Cox, G.F., Cruysberg, J.R., Curtis, M.A., Davenport, S.L., Friedrich, C.A., Kaitila, I., Krawczynski, M.R., Latos-Bielenska, A., Mukai, S., Olsen, B.R., Shinno, N., Somer, M., Vikkula, M., Zlotogora, J., Prockop, D.J., Ala-Kokko, L. Am. J. Hum. Genet. (1999)
34. Mutations in the Wolfram syndrome 1 gene (WFS1) are a common cause of low frequency sensorineural hearing loss. Bespalova, I.N., Van Camp, G., Bom, S.J., Brown, D.J., Cryns, K., DeWan, A.T., Erson, A.E., Flothmann, K., Kunst, H.P., Kurnool, P., Sivakumaran, T.A., Cremers, C.W., Leal, S.M., Burmeister, M., Lesperance, M.M. Hum. Mol. Genet. (2001)
35. Steroid-responsive postinfectious sensorineural hearing loss. Amir, N., Shalev, R.S., Berman, M., Gilai, A., Mor, J. Ann. Neurol. (1984)
36. Antimeasles immunoglobulin g for serologic diagnosis of otosclerotic hearing loss. Karosi, T., Kónya, J., Petkó, M., Szabó, L.Z., Pytel, J., Jóri, J., Sziklai, I. Laryngoscope (2006)
37. Connexin 31 (GJB3) is expressed in the peripheral and auditory nerves and causes neuropathy and hearing impairment. López-Bigas, N., Olivé, M., Rabionet, R., Ben-David, O., Martínez-Matos, J.A., Bravo, O., Banchs, I., Volpini, V., Gasparini, P., Avraham, K.B., Ferrer, I., Arbonés, M.L., Estivill, X. Hum. Mol. Genet. (2001)
38. Human Connexin 32, a gap junction protein altered in the X-linked form of Charcot-Marie-Tooth disease, is directly regulated by the transcription factor SOX10. Bondurand, N., Girard, M., Pingault, V., Lemort, N., Dubourg, O., Goossens, M. Hum. Mol. Genet. (2001)
39. The long QT syndromes: genetic basis and clinical implications. Chiang, C.E., Roden, D.M. J. Am. Coll. Cardiol. (2000)
40. Refined mapping of a gene for autosomal dominant progressive sensorineural hearing loss (DFNA5) to a 2-cM region, and exclusion of a candidate gene that is expressed in the cochlea. Van Laer, L., Van Camp, G., van Zuijlen, D., Green, E.D., Verstreken, M., Schatteman, I., Van de Heyning, P., Balemans, W., Coucke, P., Greinwald, J.H., Smith, R.J., Huizing, E., Willems, P. Eur. J. Hum. Genet. (1997)
41. A novel splice acceptor mutation in the DSPP gene causing dentinogenesis imperfecta type II. Kim, J.W., Nam, S.H., Jang, K.T., Lee, S.H., Kim, C.C., Hahn, S.H., Hu, J.C., Simmer, J.P. Hum. Genet. (2004)
42. Visual and auditory neurotoxicity in patients receiving subcutaneous deferoxamine infusions. Olivieri, N.F., Buncic, J.R., Chew, E., Gallant, T., Harrison, R.V., Keenan, N., Logan, W., Mitchell, D., Ricci, G., Skarf, B. N. Engl. J. Med. (1986)
43. Correlation between antibodies to type II collagen and treatment outcome in bilateral progressive sensorineural hearing loss. Helfgott, S.M., Mosciscki, R.A., San Martin, J., Lorenzo, C., Kieval, R., McKenna, M., Nadol, J., Trentham, D.E. Lancet (1991)
44. Impaired hearing in X-linked hypophosphataemic (vitamin-D-resistant) osteomalacia. Davies, M., Kane, R., Valentine, J. Ann. Intern. Med. (1984)
45. Cochlear implantation for the treatment of deafness. Copeland, B.J., Pillsbury, H.C. Annu. Rev. Med. (2004)
fuente: http://www.wikigenes.org/e/gene/e/63945.html
Acúfenos: Sección tratamiento, La acción antidepresiva de la natación
Aspectos moleculares involucrados en el entrenamiento con ejercicios de natación para reducir la anhedonia en un modelo de ratas con depresión.
Autores:
Andre Roberto Sigwalt1, 2, Henning Budde3, 7, Ingo Helmich4, Viviane Glaser1, Karina Ghisoni1, Silvia Lanza1, Eduardo Lusa Cadore5, Francisco Luiz Rodrigues Lhullier5, Andreza Fabro de Bem1, Alexandre Hohl6, Filipe José de Matos1, Paulo Alexandre de Oliveira8, Rui Daniel Schröder Prediger8, Luiz Guilherme Antonacci Guglielmo2 and Alexandra Latini1, Corresponding Author Contact Information, E-mail The Corresponding Author
1 Laboratório de Bioenergética e Estresse Oxidativo, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
2 Laboratório de Esforço Físico, Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
3 Department of Training and Movement Sciences, Institute of Sport Science, Humboldt Universität zu Berlin, Berlin, Germany
4 Department for Neurology, Psychosomatic and Psychiatry, Institute of health promotion and clinical movement science, German Sport University Cologne, Germany
5 Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
6 Departamento de Clínica Médica, Serviço de Endocrinologia e Metabologia, Hospital Universitário da Universidade Federal de Santa Catarina, Florianópolis, Brazil
7 Department of physical education, University of Suwon, Seoul, South Korea
8 Departamento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
Los pacientes que sufren de depresión con frecuencia muestran una hiperactividad del eje hipotálamo-hipofisario-adrenal (HPA) que resulta en niveles elevados del cortisol.
Uno de los síntomas principales de esta condición es la anhedonia. Existe evidencia de que el ejercicio puede ser utilizado como una intervención de rehabilitación en el tratamiento de los trastornos depresivos. En este escenario, el objetivo del presente estudio fue evaluar el efecto de un protocolo de ejercicio aeróbico en el comportamiento de tipo depresivo, anhedonia, inducida por la administración de dexametasona en dosis repetidas.
Anhedonia/fuente de la imagen: shockmd.com
El estudio se llevó a cabo en ratas Wistar machos adultos divididos al azar en cuatro grupos:
El "grupo de control" (C),
"grupo de ejercicio" (E),
"grupo de dexametasona" (D)
Y el "grupo de dexametasona más ejercicio" (DE).
El entrenamiento consistió en practicar natación (1 h / día, 5 días / semana) durante tres semanas, con una sobrecarga del 5% del peso corporal de la rata. Cada día las ratas fueron inyectadas con dexametasona (D / DE) o solución salina (C / E).
Se utilizaron en paralelo controles apropiadamente positivos usando fluoxetina,
. los animales tratados con dexametasona mostraban: Disminución de los niveles sanguíneos de corticosterona, reducción de la síntesis del colesterol y del peso suprarrenal adrenal (HPA interrupción), preferencia por reducir el consumo de sacarosa y mayor tiempo de inmovilidad (comportamiento símil depresivo), oxidación aumentada del ADN del hipocampo, el aumento de IL-10 y del total de factor neurotrófico derivado del cerebro (BDNF, Pro-hacia las formas maduras) y una grave pérdida de masa corporal.
fuente de la imagen: stockphotos.mx
Además de un aumento de las concentraciones de testosterona en sangre, el entrenamiento de natación protegía a las ratas depresivas del estado anhedónico, siguiendo el mismo perfil que la fluoxetina, y también de la neuroquímica alterada inducida por dexametasona. Los datos indican que el ejercicio físico puede ser una herramienta útil en la prevención y el tratamiento de los trastornos depresivos.
Fuente: http://www.sciencedirect.com/science/article/pii/S0306452211006725
Nota: (de acuerdo al articulo de http://es.wikipedia.org/wiki/Anhedonia ,La anhedonia es la incapacidad para experimentar placer, la pérdida de interés o satisfacción en casi todas las actividades. Se considera una falta de reactividad a los estímulos habitualmente placenteros. Constituye uno de los síntomas o indicadores más claros de depresión, aunque puede estar presente en otros trastornos, como por ejemplo, en algunos casos de demencias (Alzheimer).
La cultura tiene una gran influencia: una conducta puede ser aceptada por un grupo cultural y no ser bien vista por otro. Los factores biológicos son la causa principal donde se encuentran las influencias perinatales y la salud física. Es el médico psiquiatra el que determinará si es normal o anormal.
Los criterios generales para diagnosticarla como un trastorno son ver el grado de insatisfacción con las capacidades y logros del paciente, evaluar sus relaciones interpersonales y la forma en que afronta los acontecimientos de su vida. Lo importante es que el paciente aprenda a aceptar los hechos como se presentan; si su comportamiento le causa un daño a él y/o a los demás, entonces se transforma en una patología que debe ser tratada.
Autores:
Andre Roberto Sigwalt1, 2, Henning Budde3, 7, Ingo Helmich4, Viviane Glaser1, Karina Ghisoni1, Silvia Lanza1, Eduardo Lusa Cadore5, Francisco Luiz Rodrigues Lhullier5, Andreza Fabro de Bem1, Alexandre Hohl6, Filipe José de Matos1, Paulo Alexandre de Oliveira8, Rui Daniel Schröder Prediger8, Luiz Guilherme Antonacci Guglielmo2 and Alexandra Latini1, Corresponding Author Contact Information, E-mail The Corresponding Author
1 Laboratório de Bioenergética e Estresse Oxidativo, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
2 Laboratório de Esforço Físico, Centro de Desportos, Universidade Federal de Santa Catarina, Florianópolis, Brazil
3 Department of Training and Movement Sciences, Institute of Sport Science, Humboldt Universität zu Berlin, Berlin, Germany
4 Department for Neurology, Psychosomatic and Psychiatry, Institute of health promotion and clinical movement science, German Sport University Cologne, Germany
5 Exercise Research Laboratory, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
6 Departamento de Clínica Médica, Serviço de Endocrinologia e Metabologia, Hospital Universitário da Universidade Federal de Santa Catarina, Florianópolis, Brazil
7 Department of physical education, University of Suwon, Seoul, South Korea
8 Departamento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
Los pacientes que sufren de depresión con frecuencia muestran una hiperactividad del eje hipotálamo-hipofisario-adrenal (HPA) que resulta en niveles elevados del cortisol.
Uno de los síntomas principales de esta condición es la anhedonia. Existe evidencia de que el ejercicio puede ser utilizado como una intervención de rehabilitación en el tratamiento de los trastornos depresivos. En este escenario, el objetivo del presente estudio fue evaluar el efecto de un protocolo de ejercicio aeróbico en el comportamiento de tipo depresivo, anhedonia, inducida por la administración de dexametasona en dosis repetidas.
Anhedonia/fuente de la imagen: shockmd.com
El estudio se llevó a cabo en ratas Wistar machos adultos divididos al azar en cuatro grupos:
El "grupo de control" (C),
"grupo de ejercicio" (E),
"grupo de dexametasona" (D)
Y el "grupo de dexametasona más ejercicio" (DE).
El entrenamiento consistió en practicar natación (1 h / día, 5 días / semana) durante tres semanas, con una sobrecarga del 5% del peso corporal de la rata. Cada día las ratas fueron inyectadas con dexametasona (D / DE) o solución salina (C / E).
Se utilizaron en paralelo controles apropiadamente positivos usando fluoxetina,
. los animales tratados con dexametasona mostraban: Disminución de los niveles sanguíneos de corticosterona, reducción de la síntesis del colesterol y del peso suprarrenal adrenal (HPA interrupción), preferencia por reducir el consumo de sacarosa y mayor tiempo de inmovilidad (comportamiento símil depresivo), oxidación aumentada del ADN del hipocampo, el aumento de IL-10 y del total de factor neurotrófico derivado del cerebro (BDNF, Pro-hacia las formas maduras) y una grave pérdida de masa corporal.
fuente de la imagen: stockphotos.mx
Además de un aumento de las concentraciones de testosterona en sangre, el entrenamiento de natación protegía a las ratas depresivas del estado anhedónico, siguiendo el mismo perfil que la fluoxetina, y también de la neuroquímica alterada inducida por dexametasona. Los datos indican que el ejercicio físico puede ser una herramienta útil en la prevención y el tratamiento de los trastornos depresivos.
Fuente: http://www.sciencedirect.com/science/article/pii/S0306452211006725
Nota: (de acuerdo al articulo de http://es.wikipedia.org/wiki/Anhedonia ,La anhedonia es la incapacidad para experimentar placer, la pérdida de interés o satisfacción en casi todas las actividades. Se considera una falta de reactividad a los estímulos habitualmente placenteros. Constituye uno de los síntomas o indicadores más claros de depresión, aunque puede estar presente en otros trastornos, como por ejemplo, en algunos casos de demencias (Alzheimer).
La cultura tiene una gran influencia: una conducta puede ser aceptada por un grupo cultural y no ser bien vista por otro. Los factores biológicos son la causa principal donde se encuentran las influencias perinatales y la salud física. Es el médico psiquiatra el que determinará si es normal o anormal.
Los criterios generales para diagnosticarla como un trastorno son ver el grado de insatisfacción con las capacidades y logros del paciente, evaluar sus relaciones interpersonales y la forma en que afronta los acontecimientos de su vida. Lo importante es que el paciente aprenda a aceptar los hechos como se presentan; si su comportamiento le causa un daño a él y/o a los demás, entonces se transforma en una patología que debe ser tratada.
sábado, 18 de junio de 2011
Audición: Sección fisopatologia: Efectos del agotamiento brusco de Tiroxina sobre la audición humana
Effects of acute thyroxin depletion on hearing in humans†
1. Zan Mra MD1,
2. Mark K. Wax MD2,*
Author Information
1. 1
Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences Center, Portland, Oregon
2. 2
State University of New York at Buffalo, Buffalo, New York, and the Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences Center, Portland, Oregon
*Correspondence: Mark K. Wax MD, Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences University, 3181 Sam Jackson Park Road, Portland, Oregon 97201–3011, U.S.A.
1. †
Presented at the Meeting of the Southern Section of the American Laryngological, Rhinological and Otological Society, Inc., New Orleans, Louisiana, January 16, 1999.
Tiroides,
Fuente de la imagen: http://www.umm.edu/graphics/images/es/14058.jpg
Abstract
Objective: To study the physiologic effect of acute thyroid hormone depletion on hearing and the function of outer hair cells.
Design: Audiologic and otoacoustic emission testing of subjects undergoing total thyroidectomy before surgery and up to 6 weeks after surgery. Magnitude of thyroxin depletion monitored by serum thyroid-stimulating hormone levels.
Setting: Hearing research laboratory at a state university. Subjects: Ten patients undergoing total thyroidectomy.
Main Outcome Measures: Detection of hearing loss on audiogram and decrease or disappearance of otoacoustic emissions as a result of acute thyroxin depletion.
Results: No significant changes in the audiogram and otoacoustic emission configurations were detected, although thyroid-stimulating hormone levels became elevated after total thyroidectomy.
Conclusion: Although thyroid hormone is thought to play a role in the physiology of hearing in humans, no deleterious effects on hearing can be identified up to 6 weeks after thyroxin depletion
Fuente: The Laryngoscope, Volume 109, Issue 3, pages 343–350, March 1999
Mra, Z. and Wax, M. K. (1999), Effects of acute thyroxin depletion on hearing in humans. The Laryngoscope, 109: 343–350. doi: 10.1097/00005537-199903000-00001
1. Zan Mra MD1,
2. Mark K. Wax MD2,*
Author Information
1. 1
Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences Center, Portland, Oregon
2. 2
State University of New York at Buffalo, Buffalo, New York, and the Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences Center, Portland, Oregon
*Correspondence: Mark K. Wax MD, Department of Otolaryngology—Head and Neck Surgery, Oregon Health Sciences University, 3181 Sam Jackson Park Road, Portland, Oregon 97201–3011, U.S.A.
1. †
Presented at the Meeting of the Southern Section of the American Laryngological, Rhinological and Otological Society, Inc., New Orleans, Louisiana, January 16, 1999.
Tiroides,
Fuente de la imagen: http://www.umm.edu/graphics/images/es/14058.jpg
Abstract
Objective: To study the physiologic effect of acute thyroid hormone depletion on hearing and the function of outer hair cells.
Design: Audiologic and otoacoustic emission testing of subjects undergoing total thyroidectomy before surgery and up to 6 weeks after surgery. Magnitude of thyroxin depletion monitored by serum thyroid-stimulating hormone levels.
Setting: Hearing research laboratory at a state university. Subjects: Ten patients undergoing total thyroidectomy.
Main Outcome Measures: Detection of hearing loss on audiogram and decrease or disappearance of otoacoustic emissions as a result of acute thyroxin depletion.
Results: No significant changes in the audiogram and otoacoustic emission configurations were detected, although thyroid-stimulating hormone levels became elevated after total thyroidectomy.
Conclusion: Although thyroid hormone is thought to play a role in the physiology of hearing in humans, no deleterious effects on hearing can be identified up to 6 weeks after thyroxin depletion
Fuente: The Laryngoscope, Volume 109, Issue 3, pages 343–350, March 1999
Mra, Z. and Wax, M. K. (1999), Effects of acute thyroxin depletion on hearing in humans. The Laryngoscope, 109: 343–350. doi: 10.1097/00005537-199903000-00001
Sindrome de Meniere: Etiopatologia: relacion con disfunción tiroidea
Prevalencia de la disfunción tiroidea en pacientes con enfermedad de Meniere
Autores: Michael Brenner, MD, Dick Hoistad L., MD, Timothy C. Hain, MD
Departamento de Otorrinolaringología de la Universidad de Washington, St. Louis, Mo (Dr. Brenner), y los Departamentos de Otorrinolaringología (Dres. Hoistad y Hain), Neurología (Dr. Hain), y Terapia Física y Ciencias del Movimiento Humano (Dr. Hain), la Universidad de Northwestern, Chicago, Illinois,
los autores no tienen ningún interés económico correspondiente en este artículo.
Resumen
Objetivo: Determinar la prevalencia de hipotiroidismo en una población de pacientes con la enfermedad de Meniere (MD).
Diseño: Estudio retrospectivo de casos y controles, estudio que comparó el uso de suplementos de hormona tiroidea entre los pacientes con DM y los controles.
Marco: Clínica de consultas externas de neurología especializada en el manejo de pacientes que sufren mareos.
Pacientes: Cincuenta pacientes que cumplían los criterios 1995 de la Academia Americana de Otorrinolaringología para los controles de MD y 50 de la misma edad y el sexo que experimentan mareos.
Resultados: Los 50 pacientes que cumplían los criterios de MD fueron identificados a partir de una base de datos de más de 2000 pacientes con mareo visto a lo largo de un período de 5 años.
De estos, 16 (32%) tomaban suplementos de la hormona tiroidea en contraste con los 2 (4%) de los 50 controles (P 0.001).
La media de edad de los pacientes con DM fue de 60 años, y cinco (19%) de los 26 pacientes menores de 60 años tomaban suplementos de hormona tiroidea, en comparación con 11 (46%) de 24 pacientes mayores de 60 años (P 0,05).
No hubo diferencias estadísticamente significativas en la severidad de la pérdida de la audición, el patrón de pérdida de audición, o la prevalencia de pérdida auditiva bilateral entre los pacientes con MD que tomaban suplementos de hormona tiroidea y los pacientes con DM que no.
Conclusión: La enfermedad de Meniere se asocia con hipotiroidismo corregido.
La enfermedad de Ménière (MD), fue descripta por primera vez por Ménière, en 1861, es un trastorno caracterizado por episodios de vértigo, pérdida auditiva, tinnitus, y plenitud auditiva.
la asociación de MD con hidrops endolinfático es bien conocida, pero la etiología precisa de la MD se desconoce y puede ser multifactorial.
Estudios previos que intentaron determinar la prevalencia de hipotiroidismo en pacientes con MD antes que las pruebas de sensibilidad de la función tiroidea estuvieran disponibles mostraban un resultado de las estimaciones de prevalencia que varía del 3% al 17%.
Nosotros tratamos de determinar si los pacientes con DM eran más propensos a padecer de hipotiroidismo tratado, que un grupo de control de los pacientes con mareos solamente (sin MD)
MÉTODOS
Para este estudio retrospectivo (de casos y controles), se realizaron búsquedas en una base de datos informatizada de texto que consta de todas las historias de la clínica de más de 2000 pacientes atendidos durante un período de cinco años por el mismo médico (TCH) e identificó a varios cientos de registros con la mención de MD.
Los pacientes con enfermedades potencialmente confusas fueron excluidos.
Los criterios de exclusión fueron :
antecedentes de accidente cerebrovascular,
esclerosis múltiple,
la malformación de Arnold-Chiari,
trastornos psiquiátricos importantes,
convulsiones, o
alguna otra enfermedad otológica como tumor glómico, pérdida de la audición congénita, otitis media, colesteatoma, otosclerosis, fístula perilinfática, neuritis vestibular, laberintitis, vértigo postraumático, otosifilis, o cirugía de oídos anterior por una razón que no sea MD.
De este grupo de pacientes, 50 cumplían los criterios establecidos en el 1995 por la Academia Americana de ORL para MD.
De la misma base de datos de 2000-pacientes, tomamos un grupo control generado al azar, de la misma edad y sexo, de 50 pacientes con vértigo, pero sin antecedentes de pérdida de audición, tinnitus, o sensación de plenitud aural.
Todos los pacientes diagnosticados con DM fueron clasificados con:
afectación unilateral o bilateral sobre la base de los criterios diagnósticos descritos por Kitahara, , con la excepción de que, de acuerdo con la Academia Americana de 1995 los criterios de Otorrinolaringología de MD unilateral, una pérdida de audición documentada por el audiograma, no es necesario que fluctúe para ser considerada significativa.
Los pacientes con MD que habían recibido suplementos de hormona tiroidea entre sus medicamentos fueron contactados por teléfono, Se les preguntó:
sobre la causa de su enfermedad de la tiroides,
la posibilidad de una asociación de esta enfermedad con síntomas MD,
y si tenían antecedentes de enfermedades autoinmunes sistémicas.
De los 50 pacientes con mareo y pérdida significativa de la audición documentada, 16 (32%) habían tomado suplementos de tiroides en comparación con 2 (4%) en el grupo control.
La comparación de dos de las pruebas del uso de suplementos de tiroides por los pacientes con DM y un grupo control de pacientes con vértigo sin MD fue muy significativa (p 0,001).
Hubo una interacción significativa entre el uso de la tiroides y la edad entre los 50 pacientes del estudio.
Su edad media era de 60 años, y cinco (19%) de los 26 pacientes menores de 60 años tomaban suplementos de hormona tiroidea, en comparación con 11 (46%) de los 24 pacientes mayores de 60 años (P 0,05).
No hubo diferencias estadísticamente significativas en la severidad de la pérdida de la audición o la prevalencia de pérdida auditiva bilateral en los pacientes con MD que tomaban suplementos de hormona tiroidea en comparación con aquellos que no lo hacían.
Todos los 16 pacientes que tomaban suplementos de tiroides fueron contactados.
Se señaló que no hay relación temporal consistente entre la aparición de la enfermedad de la tiroides y el inicio de la MD.
Tres de los pacientes creen que los niveles elevados o deprimidos de la hormona tiroidea circulante han influido en sus síntomas MD.
Ninguno de los pacientes que toman suplementos de hormona tiroidea informó de un historial de cáncer de tiroides o una cirugía.
Además de tener hipotiroidismo corregido, 4 pacientes tenían también una de las siguientes enfermedades autoinmunes sistémicas:
1. artritis reumatoide,
2. síndrome CREST (calcinosis cutánea, fenómeno de Reynaud, dismotilidad esofágica, esclerodactilia y telangiectasias),
3. síndrome de Sjögren
4. lupus eritematoso sistémico.
COMENTARIO
1. Se encontró una tasa significativamente más alta de uso de suplementos de hormona tiroidea en los pacientes con DM (32%) que entre los controles igualados por edad y sexo (4%).
2- Más del 50% de los pacientes con MD mayores de 60 años tomaban suplementos de hormona tiroidea, lo que supera con creces la tasa de los suplementos de la hormona tiroidea en la población general.
3-No se han realizado estudios recientes de la prevalencia de la enfermedad de la tiroides en pacientes con MD. En la literatura más antigua, Pulec y House informó que el 3% de 120 pacientes con DM tenía antecedentes de hipotiroidismo y Powers encontró hipotiroidismo en el 17% de sus pacientes con MD.
Por lo tanto, nuestra encuesta más reciente muestra una mayor incidencia de hipotiroidismo.
Este hallazgo puede ser causado por la reciente disponibilidad pruebas hormonales para el hipotiroidismo de alta sensibilidad, lo que ha hecho posible que las personas con disfunción de la tiroides menos grave sean diagnosticadas y se traten.
4-Es poco probable que la asociación de la disfunción de la tiroides con la edad sea sólo un reflejo de la mayor prevalencia general de disfunción tiroidea en la población de edad avanzada, dado que la prevalencia de la enfermedad de la tiroides en las personas mayores de 55 años es inferior al 10% 0,8-11 Por lo tanto , nuestros datos apoyan la posibilidad de una prevalencia mucho mayor del uso de medicación de la tiroides en pacientes con DM en general, y una prevalencia especialmente elevada en los pacientes mayores.
5-La enfermedad tiroidea autoinmune es la enfermedad autoinmune más común en la población de los Estados Unidos, y los suplementos de tiroides tienen una alta correlación con la enfermedad.
En un estudio reciente realizado por Diez de 13655 pacientes con
• El hipotiroidismo por enfermedad de Hashimoto representaron el 47% de los casos,
• seguido de hipotiroidismo postoperatorio (26,7%),
• de causa desconocida (13,1%),
• y la terapia para un hipertiroidismo anterior (9,6%).
6- Ninguno de los pacientes que tomaban suplementos de hormona tiroidea en nuestro estudio tenía antecedentes de cirugía de la tiroides o ablación de tiroides.
Por lo tanto, la tiroiditis autoinmune es el diagnóstico más probable en nuestros pacientes que los suplementos.
Hay varias explicaciones posibles para nuestros hallazgos:
• Históricamente, un número de investigadores sugirió inicialmente que los cambios metabólicos que ocurren en el hipotiroidismo eran capaces de producir los síntomas observados en MD. sin embargo otros, más tarde rechazaron esta explicación.
• Otra posibilidad sería que la enfermedad tiroidea autoinmune directamente puede causar algunos casos de MD, sin embargo, esto también parece poco probable dado que una clara asociación entre la MD y la enfermedad autoinmune de tiroides clínicamente significativa (es decir, que requiera tratamiento) ha sido reportada en sólo un puñado de pacientes.
• Una conexión menos directa podría ser un factor de susceptibilidad compartida entre la enfermedad tiroidea autoinmune y MD.
• La Autoinmunidad sigue siendo un mecanismo potencial para algunos casos de MD. Esta idea es apoyada por nuestra observación de que cuatro de los pacientes que tomaban suplementos de hormona tiroidea había co morbilidad enfermedades autoinmunes sistémicas.
• Tanto la enfermedad tiroidea autoinmune y MD autoinmunes podrían derivar de una susceptibilidad subyacente común a las alteraciones autoinmunes.
7- Nuestros resultados demuestran una asociación entre la MD y una hipofunción tiroidea activa.
8- Los médicos deberían considerar la posibilidad de detección de la disfunción tiroidea en pacientes con DM que no están tomando suplementos.
9- La probabilidad de encontrar el hipotiroidismo es mayor en los pacientes MD mayores de 60 años.
Fuente: ARCH Otolaryngol of head and neck Surg / Vol 130, feb 2004 WWW.ARCHOTO.COM 226
Autores: Michael Brenner, MD, Dick Hoistad L., MD, Timothy C. Hain, MD
Departamento de Otorrinolaringología de la Universidad de Washington, St. Louis, Mo (Dr. Brenner), y los Departamentos de Otorrinolaringología (Dres. Hoistad y Hain), Neurología (Dr. Hain), y Terapia Física y Ciencias del Movimiento Humano (Dr. Hain), la Universidad de Northwestern, Chicago, Illinois,
los autores no tienen ningún interés económico correspondiente en este artículo.
Resumen
Objetivo: Determinar la prevalencia de hipotiroidismo en una población de pacientes con la enfermedad de Meniere (MD).
Diseño: Estudio retrospectivo de casos y controles, estudio que comparó el uso de suplementos de hormona tiroidea entre los pacientes con DM y los controles.
Marco: Clínica de consultas externas de neurología especializada en el manejo de pacientes que sufren mareos.
Pacientes: Cincuenta pacientes que cumplían los criterios 1995 de la Academia Americana de Otorrinolaringología para los controles de MD y 50 de la misma edad y el sexo que experimentan mareos.
Resultados: Los 50 pacientes que cumplían los criterios de MD fueron identificados a partir de una base de datos de más de 2000 pacientes con mareo visto a lo largo de un período de 5 años.
De estos, 16 (32%) tomaban suplementos de la hormona tiroidea en contraste con los 2 (4%) de los 50 controles (P 0.001).
La media de edad de los pacientes con DM fue de 60 años, y cinco (19%) de los 26 pacientes menores de 60 años tomaban suplementos de hormona tiroidea, en comparación con 11 (46%) de 24 pacientes mayores de 60 años (P 0,05).
No hubo diferencias estadísticamente significativas en la severidad de la pérdida de la audición, el patrón de pérdida de audición, o la prevalencia de pérdida auditiva bilateral entre los pacientes con MD que tomaban suplementos de hormona tiroidea y los pacientes con DM que no.
Conclusión: La enfermedad de Meniere se asocia con hipotiroidismo corregido.
La enfermedad de Ménière (MD), fue descripta por primera vez por Ménière, en 1861, es un trastorno caracterizado por episodios de vértigo, pérdida auditiva, tinnitus, y plenitud auditiva.
la asociación de MD con hidrops endolinfático es bien conocida, pero la etiología precisa de la MD se desconoce y puede ser multifactorial.
Estudios previos que intentaron determinar la prevalencia de hipotiroidismo en pacientes con MD antes que las pruebas de sensibilidad de la función tiroidea estuvieran disponibles mostraban un resultado de las estimaciones de prevalencia que varía del 3% al 17%.
Nosotros tratamos de determinar si los pacientes con DM eran más propensos a padecer de hipotiroidismo tratado, que un grupo de control de los pacientes con mareos solamente (sin MD)
MÉTODOS
Para este estudio retrospectivo (de casos y controles), se realizaron búsquedas en una base de datos informatizada de texto que consta de todas las historias de la clínica de más de 2000 pacientes atendidos durante un período de cinco años por el mismo médico (TCH) e identificó a varios cientos de registros con la mención de MD.
Los pacientes con enfermedades potencialmente confusas fueron excluidos.
Los criterios de exclusión fueron :
antecedentes de accidente cerebrovascular,
esclerosis múltiple,
la malformación de Arnold-Chiari,
trastornos psiquiátricos importantes,
convulsiones, o
alguna otra enfermedad otológica como tumor glómico, pérdida de la audición congénita, otitis media, colesteatoma, otosclerosis, fístula perilinfática, neuritis vestibular, laberintitis, vértigo postraumático, otosifilis, o cirugía de oídos anterior por una razón que no sea MD.
De este grupo de pacientes, 50 cumplían los criterios establecidos en el 1995 por la Academia Americana de ORL para MD.
De la misma base de datos de 2000-pacientes, tomamos un grupo control generado al azar, de la misma edad y sexo, de 50 pacientes con vértigo, pero sin antecedentes de pérdida de audición, tinnitus, o sensación de plenitud aural.
Todos los pacientes diagnosticados con DM fueron clasificados con:
afectación unilateral o bilateral sobre la base de los criterios diagnósticos descritos por Kitahara, , con la excepción de que, de acuerdo con la Academia Americana de 1995 los criterios de Otorrinolaringología de MD unilateral, una pérdida de audición documentada por el audiograma, no es necesario que fluctúe para ser considerada significativa.
Los pacientes con MD que habían recibido suplementos de hormona tiroidea entre sus medicamentos fueron contactados por teléfono, Se les preguntó:
sobre la causa de su enfermedad de la tiroides,
la posibilidad de una asociación de esta enfermedad con síntomas MD,
y si tenían antecedentes de enfermedades autoinmunes sistémicas.
De los 50 pacientes con mareo y pérdida significativa de la audición documentada, 16 (32%) habían tomado suplementos de tiroides en comparación con 2 (4%) en el grupo control.
La comparación de dos de las pruebas del uso de suplementos de tiroides por los pacientes con DM y un grupo control de pacientes con vértigo sin MD fue muy significativa (p 0,001).
Hubo una interacción significativa entre el uso de la tiroides y la edad entre los 50 pacientes del estudio.
Su edad media era de 60 años, y cinco (19%) de los 26 pacientes menores de 60 años tomaban suplementos de hormona tiroidea, en comparación con 11 (46%) de los 24 pacientes mayores de 60 años (P 0,05).
No hubo diferencias estadísticamente significativas en la severidad de la pérdida de la audición o la prevalencia de pérdida auditiva bilateral en los pacientes con MD que tomaban suplementos de hormona tiroidea en comparación con aquellos que no lo hacían.
Todos los 16 pacientes que tomaban suplementos de tiroides fueron contactados.
Se señaló que no hay relación temporal consistente entre la aparición de la enfermedad de la tiroides y el inicio de la MD.
Tres de los pacientes creen que los niveles elevados o deprimidos de la hormona tiroidea circulante han influido en sus síntomas MD.
Ninguno de los pacientes que toman suplementos de hormona tiroidea informó de un historial de cáncer de tiroides o una cirugía.
Además de tener hipotiroidismo corregido, 4 pacientes tenían también una de las siguientes enfermedades autoinmunes sistémicas:
1. artritis reumatoide,
2. síndrome CREST (calcinosis cutánea, fenómeno de Reynaud, dismotilidad esofágica, esclerodactilia y telangiectasias),
3. síndrome de Sjögren
4. lupus eritematoso sistémico.
COMENTARIO
1. Se encontró una tasa significativamente más alta de uso de suplementos de hormona tiroidea en los pacientes con DM (32%) que entre los controles igualados por edad y sexo (4%).
2- Más del 50% de los pacientes con MD mayores de 60 años tomaban suplementos de hormona tiroidea, lo que supera con creces la tasa de los suplementos de la hormona tiroidea en la población general.
3-No se han realizado estudios recientes de la prevalencia de la enfermedad de la tiroides en pacientes con MD. En la literatura más antigua, Pulec y House informó que el 3% de 120 pacientes con DM tenía antecedentes de hipotiroidismo y Powers encontró hipotiroidismo en el 17% de sus pacientes con MD.
Por lo tanto, nuestra encuesta más reciente muestra una mayor incidencia de hipotiroidismo.
Este hallazgo puede ser causado por la reciente disponibilidad pruebas hormonales para el hipotiroidismo de alta sensibilidad, lo que ha hecho posible que las personas con disfunción de la tiroides menos grave sean diagnosticadas y se traten.
4-Es poco probable que la asociación de la disfunción de la tiroides con la edad sea sólo un reflejo de la mayor prevalencia general de disfunción tiroidea en la población de edad avanzada, dado que la prevalencia de la enfermedad de la tiroides en las personas mayores de 55 años es inferior al 10% 0,8-11 Por lo tanto , nuestros datos apoyan la posibilidad de una prevalencia mucho mayor del uso de medicación de la tiroides en pacientes con DM en general, y una prevalencia especialmente elevada en los pacientes mayores.
5-La enfermedad tiroidea autoinmune es la enfermedad autoinmune más común en la población de los Estados Unidos, y los suplementos de tiroides tienen una alta correlación con la enfermedad.
En un estudio reciente realizado por Diez de 13655 pacientes con
• El hipotiroidismo por enfermedad de Hashimoto representaron el 47% de los casos,
• seguido de hipotiroidismo postoperatorio (26,7%),
• de causa desconocida (13,1%),
• y la terapia para un hipertiroidismo anterior (9,6%).
6- Ninguno de los pacientes que tomaban suplementos de hormona tiroidea en nuestro estudio tenía antecedentes de cirugía de la tiroides o ablación de tiroides.
Por lo tanto, la tiroiditis autoinmune es el diagnóstico más probable en nuestros pacientes que los suplementos.
Hay varias explicaciones posibles para nuestros hallazgos:
• Históricamente, un número de investigadores sugirió inicialmente que los cambios metabólicos que ocurren en el hipotiroidismo eran capaces de producir los síntomas observados en MD. sin embargo otros, más tarde rechazaron esta explicación.
• Otra posibilidad sería que la enfermedad tiroidea autoinmune directamente puede causar algunos casos de MD, sin embargo, esto también parece poco probable dado que una clara asociación entre la MD y la enfermedad autoinmune de tiroides clínicamente significativa (es decir, que requiera tratamiento) ha sido reportada en sólo un puñado de pacientes.
• Una conexión menos directa podría ser un factor de susceptibilidad compartida entre la enfermedad tiroidea autoinmune y MD.
• La Autoinmunidad sigue siendo un mecanismo potencial para algunos casos de MD. Esta idea es apoyada por nuestra observación de que cuatro de los pacientes que tomaban suplementos de hormona tiroidea había co morbilidad enfermedades autoinmunes sistémicas.
• Tanto la enfermedad tiroidea autoinmune y MD autoinmunes podrían derivar de una susceptibilidad subyacente común a las alteraciones autoinmunes.
7- Nuestros resultados demuestran una asociación entre la MD y una hipofunción tiroidea activa.
8- Los médicos deberían considerar la posibilidad de detección de la disfunción tiroidea en pacientes con DM que no están tomando suplementos.
9- La probabilidad de encontrar el hipotiroidismo es mayor en los pacientes MD mayores de 60 años.
Fuente: ARCH Otolaryngol of head and neck Surg / Vol 130, feb 2004 WWW.ARCHOTO.COM 226
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