Auditory neuropathy spectrum disorder: Evaluation and management

Auditory Neuropathy Spectrum Disorder Progressing with Motor and Sensory Neuropathy Caused by an ATP1A1 Variant

We encountered a 27-year-old Japanese woman with sensorineural deafness progressing to motor and sensory neuropathy. At 16 years old, she had developed weakness in her lower extremities and hearing impairment, which gradually deteriorated. At 22 years old, combined audiological, electrophysiological, and radiological examination results were consistent with auditory neuropathy spectrum disorder (ANSD). Genetic analyses identified a previously reported missense variant in the ATP1A1 gene (NM_000701.8:c.1799C>G, p.Pro600Arg). Although sensorineural deafness has been reported as a clinical manifestation of ATP1A1-related disorders, our case suggested that ANSD may underlie the pathogenesis of deafness in ATP1A1-related disorders. This case report broadens the genotype-phenotype spectrum of ATP1A1-related disorders.

Modelling cochlear mechanics

The cochlea plays a crucial role in mammal hearing. The basic function of the cochlea is to map sounds of different frequencies onto corresponding characteristic positions on the basilar membrane (BM). Sounds enter the fluid-filled cochlea and cause deflection of the BM due to pressure differences between the cochlear fluid chambers. These deflections travel along the cochlea, increasing in amplitude, until a frequency-dependent characteristic position and then decay away rapidly. The hair cells can detect these deflections and encode them as neural signals. Modelling the mechanics of the cochlea is of help in interpreting experimental observations and also can provide predictions of the results of experiments that cannot currently be performed due to technical limitations. This paper focuses on reviewing the numerical modelling of the mechanical and electrical processes in the cochlea, which include fluid coupling, micromechanics, the cochlear amplifier, nonlinearity, and electrical coupling.

Neuropatia auditiva: alerta aos pediatras

OBJETIVO: Alertar os pediatras sobre a neuropatia auditiva, doença descrita recentemente e ainda desconhecida por muitos médicos. Descrever seus fatores de risco, características clínicas e diagnósticas, com a finalidade de possibilitar uma intervenção terapêutica precoce e eficaz. FONTES DE DADOS: Realizada pesquisa nas bases de dados PubMed, Lilacs e SciELO utilizando os descritores "neuropatia auditiva" e "auditory neuropathy", entre os anos de 1996 e 2010. SÍNTESE DOS DADOS: A neuropatia auditiva, também conhecida como dessincronia auditiva, descrita em 1996, caracteriza-se clinicamente pela dificuldade na compreensão das palavras, mesmo em casos de perdas auditivas leves ou moderadas. Foi relacionada a diversas neuropatias generalizadas e fatores de risco neonatais, como internação em terapia intensiva, hiperbilirrubinemia, sepse e hipóxia. Após suspeita clínica, o diagnóstico é confirmado pela presença das emissões otoacústicas associada a um potencial evocado auditivo de tronco encefálico ausente ou alterado. Sua terapêutica permanece controversa, tendo como opções a protetização auditiva, o acompanhamento fonoterápico para habilitação ou reabilitação da linguagem e, em casos de insucesso, há relatos de resultados satisfatórios com o implante coclear. CONCLUSÕES: Enfatiza-se a importância do reconhecimento pelo pediatra da neuropatia auditiva, entidade ainda pouco citada na literatura latino-americana da especialidade.

The genetic basis of auditory neuropathy spectrum disorder (ANSD)

OBJECTIVE

Auditory neuropathy is a hearing disorder where outer hair cell function within the cochlea is normal, but inner hair cell and/or the auditory nerve function is disrupted. It is a heterogeneous disorder which can have either congenital or acquired causes. Furthermore, the aetiology of auditory neuropathy is vast, which may include prematurity, hyperbilirubinaemia, anoxia, hypoxia, congenital brain anomalies, ototoxic drug exposure, and genetic factors. It is estimated that approximately 40% of cases have an underlying genetic basis, which can be inherited in both syndromic and non syndromic conditions. This review paper provides an overview of the genetic conditions associated with auditory neuropathy spectrum disorders (ANSDs) and highlights some of the defective genes that have been found to be linked to the pathological auditory changes.

METHOD

Literature search was conducted using a number of resources including textbooks, professional journals and the relevant websites.

RESULTS

The largest proportion of auditory neuropathy spectrum disorders (ANSDs) is due to genetic factors which can be syndromic, non-syndromic or mitochondrial related. The inheritance pattern can include all the four main types of inheritances such as autosomal dominant, autosomal recessive, X-linked and mitochondrial.

CONCLUSION

This paper has provided an overview of mutation with some of the genes and/or loci discovered to be the cause for auditory neuropathy spectrum disorders (ANSDs). It has been noted that different gene mutations may trigger different pathological changes in patients with this disorder. These discoveries have provided us with vital information as to the sites of pathology in auditory neuropathy spectrum disorders (ANSDs), and the results highlight the heterogeneity of the disorder.

Presença de microfonismo coclear no peate-clique: diagnóstico diferencial entre espectro da neuropatia auditiva e perdas auditivas cocleares descendentes em crianças

TEMA: diagnóstico diferencial entre espectro da neuropatia auditiva e perdas auditivas cocleares descendentes em crianças com presença de microfonismo coclear no PEATE-clique. PROCEDIMENTOS: este relato de caso descreve os resultados da avaliação audiológica de duas crianças atendidas no Centro "Audição na Criança" da Divisão de Educação e Reabilitação dos Distúrbios da Comunicação da Pontifícia Universidade Católica de São Paulo (CeAC/DERDIC/PUCSP) que apresentaram microfonismo coclear no registro do PEATE-clique. As crianças foram submetidas às avaliações utilizando-se o PEATE-clique, o registro das emissões otoacústicas e a avaliação audiológica tonal, com a técnica da Audiometria de Reforço Visual. RESULTADOS: as avaliações comportamental, eletroacústica e eletrofisiológica revelaram que as crianças apresentam perda auditiva sensorioneural (coclear) com configuração descendente, de modo que a presença do microfonismo coclear no registro do PEATE-clique era provavelmente gerada pela preservação da cóclea nas frequências baixas. CONCLUSÃO: os casos apresentados mostram que na ausência das emissões otoacústicas e presença do microfonismo coclear, não se deve interpretar isoladamente cada exame, para que não ocorram equívocos no diagnóstico, que pode ser confundido com o Espectro da Neuropatia Auditiva. O microfonismo coclear pode aparecer em outras condições, tais como em perdas auditivas cocleares descendentes.

Auditory Evoked Potentials and Cochlear Implants: Research Findings and Clinical Applications in Children

Auditory evoked potentials can be used to objectively assess hearing sensitivity, central auditory processing, and neural encoding of speech sounds up to the level of the auditory cortex. Evoked potentials have been of interest to clinicians and researchers in the cochlear implant field for a long time because of their potential for objectively predicting cochlear implant outcomes, as well as improving candidacy determination, and implant programming. Neural response telemetry and intra-operative electrical auditory brainstem recording have been routinely performed by implant programs for many years. Recently, there has been great interest in potential clinical applications of cortical auditory evoked potentials in the implant field. Research and clinical applications are reviewed and case studies are presented that illustrate clinical applications of cortical evoked potentials in children before and after implantation.