Auditory neuropathy

Abstract

Auditory neuropathy (auditory dys-synchrony, AN/AD) is the name for a newly diagnosed independent nosological unit used in evaluating sensoric-neural defects of hearing. A common sensorineural hearing impairment classically originates as a damage of hair cells of inner ear with well-preserved function of auditory nerve. AN/AD is defined as an opposite condition. The existence of hair cells in cochlear is confirmed as well as their motor functionality in processing of auditory signal, but functionality of auditory nerve is severely damaged. The diagnosis if based on mutual comparison of two objective methods of examination - acoustic emissions (OAE) (particularly the transitory effect) and measurement of the stem evoked potentials (ABR). The stem potentials are always affected, which according present evaluation corresponds to very severe hearing defect or deafness. In contrast to that OAE are always fully equipped, therefore correspond to the finding in normal state of hearing. The paper presents present knowledge of these special types of sensorineural hearing defects. A similar type of hearing defect (normal OAE and simultaneously affected ABR) in the smallest children is most often encountered in those who suffered from perinatal damage: premature delivery, low birth weight, asphyxia etc. From the AN/AD conclusions is follows, as is presently considered as standard in the world (especially in the U.S.A.) is to examine, while determining hearing state in the smallest children, in a combination of OAE and ABR. The use of a single method only, although quite widespread, is apparently insufficient based on the AN/AD knowledge and could result in a significant distortion of results evaluating hearing state in the smallest children.