Auditory neuropathy or endocochlear hearing loss?

Aims: The purpose of the study was to define boundaries between endocochlear hearing loss and auditory neuropathy in children with congenital profound hearing loss and positive otoacoustic emissions.

Patient: A child presented with bilateral profound hearing loss, which was confirmed by the absence of evoked auditory potentials at 110 dB and with conserved otoacoustic emissions. The lack of any relevant medical history, a normal neurologic pediatric examination, and the improvement obtained with powerful hearing aids suggested an endocochlear cause. Genetic testing identified mutations in OTOF, responsible for the DFNB9 recessive form of hearing loss.

Results: In recent years, cases of children with hearing loss associated with positive otoacoustic emissions have been labeled as "auditory neuropathy." Classically, this form of hearing loss is refractory to the use of hearing aids and cochlear implants. Mutations in OTOF lead to inner hair cells dysfunction, whereas the outer hair cells are initially functionally preserved. As this form of endocochlear hearing loss can be detected at a molecular level, genetic testing can be proposed for cases of nonsyndromic auditory neuropathy, as those children could benefit from cochlear implantation.

Conclusion: It is advisable to reserve the term "auditory neuropathy" for patients who present hearing loss and conserved otoacoustic emissions in the context of a neurologic syndrome or for children with suggestive perinatal history. In other cases, genetic testing for mutations in OTOF should be carried out.