ABSTRACT
Abstract Introduction: Auditory Neuropathy/Dyssynchrony is a disorder characterized by the presence of Otoacoustic Emissions and Cochlear Microphonic Potentials, an absence or severe alteration of Brainstem Evoked Auditory Potential, auditory thresholds incompatible with speech thresholds and altered acoustic reflexes. The study of the Cochlear Microphonic Potential appears to be the most important tool for an accurate diagnosis of this pathology. Objective: Determine the characteristics of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony using an integrative review. Methods: Bibliographic survey of Pubmed and Bireme platforms and MedLine, LILACS and SciELO data banks, with standardized searches up to July 2014, using keywords. Criteria were established for the selection and assessment of the scientific studies surveyed, considering the following aspects: author, year/place, degree of recommendation/level of scientific evidence, objective, sample, age range, mean age, tests, results and conclusion. Results: Of the 1959 articles found, 1914 were excluded for the title, 20 for the abstract, 9 for the text of the article, 2 for being repeated and 14 were selected for the study. Conclusion: The presence of the Cochlear Microphonic is a determining finding in the differential diagnosis of Auditory Neuropathy/Dyssynchrony. The protocol for the determination of Cochlear Microphonic must include the use of insert earphones, reverse polarity and blocking the stimulus tube to eliminate electrical artifact interference. The amplitude of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony shows no significant difference from that of normal individuals. The duration of the Cochlear Microphonic is longer in individuals with Auditory Neuropathy/Dyssynchrony.
Resumo Introdução: A Neuropatia/Dessincronia Auditiva é uma doença caracterizada pela presença das Emissões Otoacústicas e do Microfonismo Coclear, com ausência ou grave alteração do Potencial Evocado Auditivo de Tronco Encefálico, limiares auditivos incompatíveis com limiares vocais e reflexos acústicos alterados. O estudo do Microfonismo Coclear parece ser a ferramenta mais importante para um diagnóstico preciso desta patologia. Objetivo: Verificar por meio de uma revisão integrativa as características do Microfonismo Coclear na Neuropatia/Dessincronia Auditiva. Método: Levantamento bibliográfico nas plataformas Pubmed e Bireme e nas bases de dados MedLine, LILACS e SciELO, com buscas padronizadas até julho de 2014, utilizando-se palavraschave. Para a seleção e avaliação dos estudos científicos levantados, foram estabelecidos critérios, contemplando os aspectos: autor, ano/local, grau de recomendação/nível de evidência científica, objetivo, amostra, faixa etária, média de idade em anos, testes, resultados e conclusão. Resultados: Dos 1959 artigos encontrados, 1914 foram excluídos pelo título, 20 pelo resumo, nove pela leitura do artigo, dois eram repetidos e 14 foram selecionados para o estudo. Conclusão: A presença do Microfonismo Coclear é um achado determinante no diagnóstico diferencial da Neuropatia/Dessincronia auditiva. O protocolo de registro do Microfonismo Coclear deve contar com o uso de fones de inserção, a inversão da polaridade e o bloqueio do tubo do estímulo para impedir a interferência de artefato elétrico. A amplitude do Microfonismo Coclear na Neuropatia/Dessincronia auditiva não apresenta diferença significante entre a amplitude do Microfonismo Coclear em ouvintes normais. A duração do Microfonismo Coclear é maior em indivíduos com Neuropatia/Dessincronia auditiva.
Subject(s)
Humans , Auditory Threshold/physiology , Evoked Potentials, Auditory, Brain Stem/physiology , Otoacoustic Emissions, Spontaneous/physiology , Cochlear Microphonic Potentials/physiology , Hearing Loss, Central/physiopathologyABSTRACT
INTRODUCTION: Auditory Neuropathy/Dyssynchrony is a disorder characterized by the presence of Otoacoustic Emissions and Cochlear Microphonic Potentials, an absence or severe alteration of Brainstem Evoked Auditory Potential, auditory thresholds incompatible with speech thresholds and altered acoustic reflexes. The study of the Cochlear Microphonic Potential appears to be the most important tool for an accurate diagnosis of this pathology. OBJECTIVE: Determine the characteristics of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony using an integrative review. METHODS: Bibliographic survey of Pubmed and Bireme platforms and MedLine, LILACS and SciELO data banks, with standardized searches up to July 2014, using keywords. Criteria were established for the selection and assessment of the scientific studies surveyed, considering the following aspects: author, year/place, degree of recommendation/level of scientific evidence, objective, sample, age range, mean age, tests, results and conclusion. RESULTS: Of the 1959 articles found, 1914 were excluded for the title, 20 for the abstract, 9 for the text of the article, 2 for being repeated and 14 were selected for the study. CONCLUSION: The presence of the Cochlear Microphonic is a determining finding in the differential diagnosis of Auditory Neuropathy/Dyssynchrony. The protocol for the determination of Cochlear Microphonic must include the use of insert earphones, reverse polarity and blocking the stimulus tube to eliminate electrical artifact interference. The amplitude of the Cochlear Microphonic in Auditory Neuropathy/Dyssynchrony shows no significant difference from that of normal individuals. The duration of the Cochlear Microphonic is longer in individuals with Auditory Neuropathy/Dyssynchrony.
Subject(s)
Auditory Threshold/physiology , Cochlear Microphonic Potentials/physiology , Evoked Potentials, Auditory, Brain Stem/physiology , Hearing Loss, Central/physiopathology , Otoacoustic Emissions, Spontaneous/physiology , HumansABSTRACT
El desorden del espectro de neuropatía auditiva (DENA) describe una condición en la cual se observa o se ha observado emisiones otoacústicas (EOA) junto con potenciales evocados auditivos de tronco (PEAT) anormales o ausentes. Su identificación se basa en la presencia de potencial microfónico coclear (PMIC) junto con un PEAT anormal o ausente y EOA presentes o antecedentes de su presencia. Los umbrales tonales pueden encontrarse entre los rangos de normalidad hasta pérdidas auditivas profundas. El reconocimiento del habla generalmente se encuentra afectado particularmente en presencia de ruido de fondo, sin embargo en algunos individuos se mantiene conservado (sin ruido). Se presenta caso clínico de un recién nacido de sexo femenino de pretérmino de 29 semanas y 810 grs (GIII), apgar 7/8, presenta displasia broncopulmonar, sospecha de infección connatal tratada, hiperbilirrubinemia (max 11 mg/dl) tratada con fototerapia. Es derivada al Servicio de Otorrinolaringología para su evaluación auditiva. La evaluación auditiva realizada corresponde a potenciales evocados auditivos de tronco (PEAT), impedanciometria, audiometría de campo de respuesta reflejas y emisiones oto-acústicas. Los resultados obtenidos concuerdan con lo descrito en la literatura para un DENA.
Auditory neuropathy spectrum disorder (ANSD) describes a condition in which it is possible to find otoacoustic emissions (OAE) in presence of abnormal or absent auditory brainstem evoked potentials (ABR). The pure tone thresholds may show a spectrum from normal to profound hearing loss. Speech recognition is often affected in presence of background noise, but in some individuals remains intact. We report a case of a pre term newborn (female) of 29 weeks and 810 grams, Apgar 7/8, bronchopulmonary dysplasia, suspected connatal infection, and hyperbilirubinemia (max 11 mg / dl). She was referred to Hospital Padre Hurtado for hearing assessment. The hearing test performed were an ABR, tympanometry & acoustic reflex, visual reinforcement audiometry and otoacoustic emissions. The results are consistent with those described in the literature for ANSD.
Subject(s)
Humans , Female , Infant, Newborn , Evoked Potentials, Auditory, Brain Stem/physiology , Hearing Tests/methods , Hearing Loss, Central/diagnosis , Hearing Loss, Central/physiopathology , Electrophysiology , Cochlear Microphonic Potentials/physiology , Infant, PrematureABSTRACT
The mammalian cochlea has two types of sensory cells; inner hair cells, which receive auditory-nerve afferent innervation, and outer hair cells, innervated by efferent axons of the medial olivocochlear (MOC) system. The role of the MOC system in hearing is still controversial. Recently, by recording cochlear potentials in behaving chinchillas, we suggested that one of the possible functions of the efferent system is to reduce cochlear sensitivity during attention to other sensory modalities (Delano et al. in J Neurosci 27:4146-4153, 2007). However, in spite of these compelling results, the physiological effects of electrical MOC activation on cochlear potentials have not been described in detail in chinchillas. The main objective of the present work was to describe these efferent effects in the chinchilla, comparing them with those in other species and in behavioral experiments. We activated the MOC efferent axons in chinchillas with sectioned middle-ear muscles by applying current pulses at the fourth-ventricle floor. Auditory-nerve compound action potentials (CAP) and cochlear microphonics (CM) were acquired in response to clicks and tones of several frequencies, using a round-window electrode. Electrical efferent stimulation produced CAP amplitude suppressions reaching up to 11 dB. They were higher for low to moderate sound levels. Additionally, CM amplitude increments were found, the largest (≤ 2.5 dB) for low intensity tones. CAP suppression was present at all stimulus frequencies, but was greatest for 2 kHz. CM increments were highest for low-frequency tones, and almost absent at high frequencies. We conclude that the effect obtained in chinchilla is similar to but smaller than that observed in cats, and that the effects seen in awake chinchillas, albeit different in magnitude, are consistent with the activation of efferent fibers.
Subject(s)
Action Potentials , Auditory Cortex/physiology , Cochlea/physiology , Cochlear Microphonic Potentials , Animals , Cats , Chinchilla , Efferent Pathways , Guinea PigsABSTRACT
UNLABELLED: The brainstem auditory evoked potential (BAEP) is being extensively used as a method for the evaluation of cochlear function in individuals with diagnosis of auditory neuropathy/auditory dyssynchrony (AN/AD). In the absence of otoacoustic emissions, many cases of AN/AD have been diagnosed by the presence of CM identified in the BAEP. AIM: to demonstrate the clinical applicability of extratympanic electrocochleography (ET-Ecochg) in the differential diagnosis of AN/AD compared to the BAEP. METHOD: a 4-year-old child with a diagnosis of AN/AD seen at the Audiological Research Center was submitted to ET-Ecochg with a 2000 Hz tone burst in rarefaction and condensation polarities. RESULTS: the ET-Ecochg exam was illustrated. Using an appropriate protocol, it was possible to demonstrate CM and to confirm it in the Ecochg, with a recording quality superior to that obtained in the BAEP. CONCLUSION: ET-Ecochg permitted a more detailed analysis of CM compared to the BAEP, thus showing clinical applicability for the investigation of cochlear function in AN/AD.
Subject(s)
Auditory Perceptual Disorders/diagnosis , Cochlear Microphonic Potentials/physiology , Electrophysiology/methods , Evoked Potentials, Auditory, Brain Stem/physiology , Hearing Loss/diagnosis , Vestibulocochlear Nerve Diseases/diagnosis , Auditory Perceptual Disorders/physiopathology , Child, Preschool , Diagnosis, Differential , Female , Humans , Reproducibility of Results , Vestibulocochlear Nerve Diseases/physiopathologyABSTRACT
O potencial evocado auditivo de tronco encefálico (PEATE) vem sendo amplamente utilizado como método para avaliação da função coclear em indivíduos com diagnóstico de neuropatia/dessincronia auditiva (NA/DA). Na ausência das emissões otoacústicas, muitos casos de NA/DA foram diagnosticados pela presença do microfonismo coclear (MC) identificado no PEATE. OBJETIVO: Demonstrar a aplicabilidade clínica da eletrococleografia extratimpânica (Ecog-ET) no diagnóstico diferencial da NA/DA quando comparada ao PEATE. MATERIAL E MÉTODO: Uma criança com 4 anos de idade, com diagnóstico de NA/DA atendida no Centro de Pesquisas Audiológicas realizou a Ecog-ET com tone burst de 2000Hz nas polaridades de rarefação e condensação. RESULTADOS: Ilustrou-se o registro da Ecog-ET. Com a utilização de protocolo apropriado, o MC pode ser evidenciado e confirmado na Ecog, com qualidade de registro superior ao obtido no PEATE. CONCLUSÃO: A Ecog-ET permitiu uma análise mais detalhada do MC quando comparada ao PEATE tendo, portanto aplicabilidade clínica na investigação da função coclear na NA/DA.
The brainstem auditory evoked potential (BAEP) is being extensively used as a method for the evaluation of cochlear function in individuals with diagnosis of auditory neuropathy/auditory dyssynchrony (AN/AD). In the absence of otoacoustic emissions, many cases of AN/AD have been diagnosed by the presence of CM identified in the BAEP. AIM: to demonstrate the clinical applicability of extratympanic electrocochleography (ET-Ecochg) in the differential diagnosis of AN/AD compared to the BAEP. METHOD: a 4-year-old child with a diagnosis of AN/AD seen at the Audiological Research Center was submitted to ET-Ecochg with a 2000 Hz tone burst in rarefaction and condensation polarities. RESULTS: the ET-Ecochg exam was illustrated. Using an appropriate protocol, it was possible to demonstrate CM and to confirm it in the Ecochg, with a recording quality superior to that obtained in the BAEP. CONCLUSION: ET-Ecochg permitted a more detailed analysis of CM compared to the BAEP, thus showing clinical applicability for the investigation of cochlear function in AN/AD.
Subject(s)
Child, Preschool , Female , Humans , Auditory Perceptual Disorders/diagnosis , Cochlear Microphonic Potentials/physiology , Electrophysiology/methods , Evoked Potentials, Auditory, Brain Stem/physiology , Hearing Loss/diagnosis , Vestibulocochlear Nerve Diseases/diagnosis , Auditory Perceptual Disorders/physiopathology , Diagnosis, Differential , Reproducibility of Results , Vestibulocochlear Nerve Diseases/physiopathologyABSTRACT
Este estudo avaliou a função coclear e neural em indivíduos com neuropatia/dessincronia auditiva. Vinte e seis orelhas foram analisadas: grupo controle (n=10) e grupo estudo (n=16). Os grupos apresentaram resultados semelhantes em relação à amplitude do microfonismo coclear. No grupo estudo, o microfonismo coclear teve início atrasado, mas sem diferença estatisticamente significante. Houve diferenças estatísticas em relação aos parâmetros de término e duração do microfonismo coclear...
This study evaluated the cochlear and neural functions in individuals with auditory neuropathy/dyssynchrony.. Twenty-six ears were analyzed: the control group (n=10) and the study group (n=16). The groups present similar results in relation to the amplitude of the cochlear microphonic. In the study group, the cochlear microphonic had a late beginning but with no statistical significance. There were statistical differences in relation to the ending and duration parameters of the cochlear microphonic...
Subject(s)
Male , Female , Infant , Child, Preschool , Child , Humans , Audiometry, Evoked Response , Cochlear Microphonic Potentials , Hearing Loss , ChildABSTRACT
These experiments were designed to investigate the effect of noise, sleep, and gentamicin on the cochlear microphonic (CM) of the guinea pigs. Are the changes observed due to intrinsic cochlear phenomena or to efferent system actions? To answer this question, noise exposure together with efferent system blockade by gentamicin administration was performed. In the normal (non-treated) animal, noise exposure decreased both variability and amplitude of the tone evoked CM in about the first 10 min while the physiological modulation of slow wave sleep increasing the CM is not present. Following administration of gentamicin, noise no longer affect the CM in about the first 10 min, although it produces amplitude and variability increments. The influence of slow wave sleep on the CM is not altered. Thus, gentamicin does not block the CM sleep/wakefulness related shifts. The data were discussed in terms of the influence of gentamicin on the olivo-cochlear bundle. It was hypothesized that the effects of noise on the CM is a result of both peripheral and central influences.
Subject(s)
Anti-Bacterial Agents/adverse effects , Cochlear Microphonic Potentials/physiology , Gentamicins/adverse effects , Noise/adverse effects , Sleep/physiology , Wakefulness/physiology , Animals , Anti-Bacterial Agents/administration & dosage , Cochlear Microphonic Potentials/drug effects , Efferent Pathways/drug effects , Efferent Pathways/physiology , Gentamicins/administration & dosage , Guinea PigsABSTRACT
Através das emissões otoacústicas pré e pós operatória foi avaliada a inativação da contração das células ciliadas externas pela ação da toxina botulínica A. No grupo de estudo aplicou-se uma unidade de toxina botulínica sobre a janela redonda de oito chinchilas. O grupo controle usou soro fisiológico. As emissões otoacústicas estiveram ausentes nos exames pós operatórios de todas as orelhas do grupo de estudo e estiveram presentes em todos os exames pós-operatórios do grupo controle. Esses resultados sugerem que a toxina botulínica pode ser uma eficiente ferramenta para o estudo das vias eferentes cocleares, pois a cirurgia é de fácil realização e não requer a intervenção intracerebral.The action of botulinum toxin A inactivating the contraction of the outer hair cells was evaluated by pre and postoperative otoacoustic emissions exams. In the study group, one unit of toxin was applied onto the round window of eight chinchillas. The control group was submitted to saline solution. Otoacoustic emissions were absent in all postoperative exams of the study group, in contrast to the control group. Those results suggest that botulinum toxin can be an efficient tool for the study of efferent auditory pathways. The surgery can be easily done without an intracranial intervention...
Subject(s)
Animals , Cochlea/surgery , Neurons, Efferent/physiology , Receptors, Cholinergic/metabolism , Botulinum Toxins, Type A/administration & dosage , Chinchilla , Auditory Threshold , Cochlear Microphonic PotentialsSubject(s)
Humans , Male , Female , Ear, Inner/anatomy & histology , Ear, Inner/physiology , Cochlear Microphonic Potentials , Sound Localization , Efferent Pathways/anatomy & histology , Hearing/physiology , Cochlea/pathology , Endolymphatic Hydrops , Endolymphatic Hydrops/diagnosis , Metabolism , Hearing Loss, Sensorineural , Hearing Loss, Sensorineural/classification , Hearing Loss, Sensorineural/diagnosis , Hearing Loss, Sensorineural/therapy , Cochlear Diseases/classification , Cochlear Diseases/diagnosis , Infection Control , Tinnitus , Tinnitus/classification , Tinnitus/diagnosis , Hearing Loss, Noise-Induced , Cochlear Implants , Correction of Hearing ImpairmentABSTRACT
Introduçäo: As emissöes otoacústicas refletem, preferencialmente, o status funcional da cóclea. Como a passagem da informaçäo sonora, tanto em sua direçäo aferente quanto na eferente, depende também das condiçöes da orelha média, säo vários os fatores que podem regular o registro final das emissöes otoacústicas. Objetivos: Este estudo teve o objetivo de verificar o comportamento das respostas cocleares captadas através de EOAT e de EOAPD em adultos jovens e em idosos com funçäo normal de orelha média, observando-se a amplitude das respostas nas duas condiçöes. Resultados: Foram analisados os resultados obtidos em 40 orelhas de 20 adultos jovens entre 20 e 25 anos de idade, e de 30 orelhas de 15 idosos entre 60 e 75 anos de idade, ambos os grupos sem queixa auditiva e com nível de audiçäo dentro dos limites da normalidade. Conclusäo: Comparando-se as emissöes otoacústicas transientes (EOATs) com as emissöes otoacústicas por produto de distorçäo (EOAPD), as primeiras sofreram maiores impedimentos em sua captaçäo, tanto em adultos jovens quanto em idosos
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Otoacoustic Emissions, Spontaneous/physiology , Cochlear Microphonic Potentials/physiology , Hearing/physiology , Auditory Perception , Acoustic Stimulation/methodsSubject(s)
Humans , Child , Evoked Potentials, Auditory , Cochlear Microphonic Potentials , Hearing Tests , Mass ScreeningABSTRACT
Introducción. Este estudio fue realizado con el fin de conocer la prevalencia de las emisiones otoacústicas espontáneas y provocadas por sonidos transitorios en la población pediátrica de alto riesgo. Material y métodos. Se examinaron 44 niños con edad promedio de 3.7 años, en quienes se comprobó que tenían audición normal y que estaban libres de infecciones y disfunciones del oído medio. Resultados. Se encontró una prevalencia de 56.8 por ciento de emisiones otoacústicas espontáneas y un 73.8 por ciento de emisiones otoacústicas provocadas. Estos resultados son comparables con los encontrados por otros autores en poblaciones similares. Conclusiones. Este método diagnóstico, además de ser un procedimiento rápido comparado con los potenciales provocados auditivos de tallo cerebral y la electrococleografía, nos informa sobre la función coclear con el fin de obtener una detección temprana de alteraciones auditivas, aún las que no son permanentes, como sucede en los cambios temporales que resultan de la ototoxicidad. Además separa las lesiones colcleares de las neurológicas, o madurativas, de la vía auditiva por ser una señal preneural
Subject(s)
Child , Humans , Male , Female , Cochlea/physiology , Otoacoustic Emissions, Spontaneous/physiology , Cochlear Microphonic Potentials/physiologyABSTRACT
Al estimular el oído con dos tonos puros simultáneos (primarios), se obtienen respuestas cocleares no sólo a los tonos primarios sino también a productos de distorsión (PDs) con frecuencia que son combinaciones de las frecuencias de los estímulos. Estos PDs han sido estudiados en experimentos psicofísicos, en registros de fibras aisladas del nervio coclear y mas recientemente en emisiones otoacústicas medidas en el meato externo. Hemos montado la técnica de medición de PDs en emisiones otoacústicas en la chinchilla usando una sonda acústica construida en nuestro laboratorio. Se presentaron simultáneamente dos tonos primarios en el conducto auditivo externo por medio de fonos miniatura ubicados en la sonda. Esta presión se amplificó, se muestreó y se analizó para obtener sus componentes espectorales. Resultados obtenidos en 8 chinchillas muestran que, para tonos primarios (1 y 2) con frecuencias entre 2 kHz y 8 kHz, se registran PDs a frecuencias tanto menores (p.ej., 21-2), como mayores (p.ej., 22-1), que las de los tonos primarios. Los PDs a 21-2 alcanzan niveles de hasta 24 dB bajo el nivel de los tonos primarios, mientras que los de frecuencia 22-1 son de menor intensidad. Se discuten algunas aplicaciones clínicas de las emisiones de PDs en humanos
Subject(s)
Animals , Cochlea/physiology , Otoacoustic Emissions, Spontaneous/physiology , Chinchilla/physiology , Acoustic Stimulation/methods , Cochlear Microphonic Potentials/physiologyABSTRACT
Gross cochlear potentials in response to alternating clicks and pure tone bursts were recorded in guinea-pigs with chronically implanted electrodes in the round window during sleep and the awake state. A significant increase in both averaged potentials, the compound auditory nerve action potential (cAP) and cochlear microphonics (CM) occurred in slow wave sleep (SWS) with a subsequent diminution in paradoxical sleep (PS) periods. The cAP, CM, amplitude and area averages were similar during quiet wakefulness and in PS. Moreover, as an episode of PS progressed, the recorded potentials continued to decrease. On the other hand, increased averaged values were again observed during a subsequent episode of SWS. An involvement of the efferent olivo-cochlear bundle is postulated, first, because it is the only known pathway connecting the CNS and the auditory periphery and, second, because several key pre-receptor variables (middle ear muscles and ossicles and sound-source ear relation) were either abolished or altered dramatically.
Subject(s)
Cochlear Microphonic Potentials , Evoked Potentials, Auditory , Sleep Stages/physiology , Vestibulocochlear Nerve/physiology , Acoustic Stimulation , Action Potentials , Animals , Guinea Pigs , Neurons, Efferent/physiology , Round Window, Ear/physiology , Theta Rhythm , Wakefulness/physiologyABSTRACT
The effects of furosemide and xipamide on guinea pig cochlear potentials were studied under acute conditions. Auditory nerve action potentials (AP) and cochlear microphonics (CM) were depressed by both diuretics in a dose-related manner. Furosemide was more effective on AP than on CM. In contrast, the xipamide-induced reductions of AP and CM were similar. Our results suggest that the depressive effects of furosemide or xipamide may be related to a direct action on cochlear mechanisms.
Subject(s)
Cochlear Microphonic Potentials/drug effects , Diuretics/toxicity , Evoked Potentials, Auditory/drug effects , Furosemide/toxicity , Xipamide/toxicity , Action Potentials/drug effects , Animals , Cochlea/drug effects , Cochlea/physiopathology , Guinea Pigs , Vestibulocochlear Nerve/drug effects , Vestibulocochlear Nerve/physiopathologySubject(s)
Evoked Potentials , Nervous System Diseases/diagnosis , Brain Stem/physiopathology , Child, Preschool , Cochlear Microphonic Potentials , Electroretinography , Evoked Potentials, Auditory , Evoked Potentials, Somatosensory , Evoked Potentials, Visual , Forensic Medicine , Humans , Infant , Infant, Newborn , Meniere Disease/diagnosis , Neuroma, Acoustic/diagnosis , Reaction Time , Visual Pathways/physiopathologyABSTRACT
A head holder for guinea-pigs to be used in posterior fossa or cochlear surgery and electrophysiological recordings is described. Cochlear microphonic and auditory nerve potentials are shown.