gms | German Medical Science

A hearing impairment in which otoacoustic emissions can be registered, but acoustic evoked electrical potentials are absent or only recordable with elevated thresholds, is denoted as auditory neuropathy or perisynaptic audiopathy. Patients typically show insufficient speech understanding relative to the measured pure-tone thresholds which is often extremely variable. Although this disease is quite rare, it is topical for discussion currently because babies with a perisynaptic audiopathy will not be identified via the conventional newborn hearing-screening based on otoacoustic emissions alone and because of the possibility of cochlear implantation (CI), with various outcomes being reported by different authors.

We compared eight patients with a perisynaptic audiopathy after cochlear implantation to a matched pair control group of implanted patients without the disease with respect to: age at evaluation; age at onset of the hearing loss; duration of the hearing impairment; hearing aid use and the success of the hearing aid use. We compared the results of subjective and objective audiometry results for both groups. The success of the cochlear implantation was assessed and compared using speech understanding tests.

Independent from the age of patients a complete audiometry – incl. invasive audiometry – is possible. The use of electrocochleography allows the clinician to differentiate between the affected patients in greater detail. Registrating a low threshold with Cochlear Micrphonics and Compound Action Potentials but no Auditory Electrical Potentials is suspicious for a neuropathy. In all patients with perisynaptic audiopathy the outcome with CI is positive and not in all cases inferior than in the control patients.

A perisynaptic audiopathy can be due to an isolated defect of the inner hair cells, defective postsynaptic transfer and/or spiral ganglion cells. For this reason, a variety of diagnostic tools should be used. Whether the different reasons for perisynaptic audiopathy have an effect on the success of a cochlear implantation is a topic for further research involving larger groups of affected patients.