[Auditory neuropathy (auditory neuropathy spectrum disorders): the approaches to diagnostics and rehabilitation]

Auditory neuropathies (auditory neuropathy spectrum disorders, ANSD) may be a consequence of dysfunction of inner hair cells and/or of synapses between these cells and auditory nerve fibers. Another cause of these disorders is supposed to be pathological changes in the auditory nerve itself. The outcome of the rehabilitative treatment of the patients presenting with this disorder depends on the quality of diagnosis and precise location of the pathological process. The present study involved 82 patients with auditory neuropathies. The audiological data obtained in the course of this work were compared with the results of other authors published during the recent years. The objective audiological examination included electrocochleography, registration of auditory brainstem response (ABR) and otoacoustic emission of short-latency and long-latency evoked auditory nerve action potentials. High-amplitude cochlear microphonic and transient evoked otoacoustic emission (TEOAE) potentials were recorded in 82 patients. In 17 (20.7%) patients, otoacoustic emission disappeared in the course of time even though the microphonic potential remained stable. It was shown that the results of electrical acoustic correction in the patients exhibiting long-latency evoked auditory action potentials and positive ABR to electrical stimulation (positive promontory test) were better than in the remaining cases. The outcome of cochlear implantation to a large extent depended on the localization of the pathological process. Specifically, the results of the treatment of the patients with high-amplitude summation potentials, prolonged latency, and positive auditory action potentials in response to electrical stimulation (typical of pre-synaptic localization of the pathological process) were better than in the patients with normal summation potentials, pathological auditory nerve action potentials, TEOAE, and negative ABR to electrical stimulation (indicative of post-synaptic localization of the pathological process). In the latter group of patients, the results of cochlear implantation were far from being satisfactory. It is concluded that additional information facilitating categorization of the pathological process can be obtained by the identification of the genetic mutations responsible for the development of auditory neuropathies.