Hearing neuropathy9/28/2023 In subjects with normal hearing, repeatable auditory brainstem response waveforms can be reliably obtained to acoustic click and tone-burst stimuli presented at levels around 10–20 dBnHL ( Hyde et al., 1990 Durieux-Smith et al., 1991 Stapells et al., 1994). In recent times, however, the combination of preneural physiologic measures such as the cochlear microphonic and the otoacoustic emission, with neural responses such as the compound action potential and auditory brainstem response has made it possible to identify neural transmission disorders in subjects with cochlear (outer hair cell) function.Īuditory Brainstem Responses in Ears with Normal Hearing and Sensorineural Hearing LossĪuditory brainstem response testing has been in widespread use as both a hearing screening and diagnostic measure for over 25 years. Such losses, which can produce the auditory neuropathy/dys-synchrony result profile, have (until the advent of preneural assessment techniques) been indistinguishable from those centered at the cochlea. Hearing deficit can also be the result of abnormal transmission of neural signals through the auditory pathway or disordered processing of those signals in the auditory brainstem. The last term has been used in recognition that some cochlear losses may also involve damage to neural elements that occur, for example, as a result sensory deprivation. Cochlear level hearing deficit is variously referred to as sensory, inner ear, hair cell, cochlear, and sensorineural hearing loss. The most common form of permanent hearing loss is the result of an abnormality at the level of the cochlea and can be related to a loss or malfunction of the inner hair cells, loss or malfunction of the cochlear amplifier (which is thought to reside in the outer hair cells and provide an increase in hearing sensitivity of up to 30–40 dB) or a disruption of the driving force for the inner hair cell, known as the endocochlear potential ( Ryan and Dallos, 1975). The final tracings, in which only the stimulus artefact is evident, were obtained to rarefacting clicks presented with the tubephone clamped.ĭecreased hearing sensitivity can result from dysfunction occurring at various sites in the peripheral and central auditory pathways. The asterisks indicate the positive peaks in the cochlear microphonic waveform. The middle tracing pairs show repeatable cochlear microphonic responses but absent brain stem response waveforms to unipolar stimuli at 80 dBnHL. The top tracings show no repeatable potentials to alternating clicks presented at 100 dBnHL. The dotted line represents the point at which the stimulus reached the cochlea. ABR recordings for a 3-year-old child with AN/AD type hearing loss.
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