Involvement of peripheral vestibular nerve in individuals with auditory neuropathy.

The vestibulocochlear nerve is a sensory nerve that serves the organs of hearing and equilibrium. Neuropathies of the nerve, particularly auditory neuropathy may be caused by primary demyelination or by axonal diseases. In disorders affecting the cochlear nerve, it is probable that the vestibular nerve is involved as well. There are isolated reports of the involvement of the inferior vestibular nerve (using vestibular-evoked myogenic potentials) in individuals with AN. However, there is a dearth of information on the involvement of the superior vestibular nerve and other functions such as optokinetic, saccade and vestibulo-occular reflex. A total of three subjects diagnosed as having auditory neuropathy, underwent an extensive vestibular assessment consisting of clinical tests of stability (Romberg, Fukuda stepping test), administration of dizziness questionnaire developed by Maryland hearing and balance centre, cervical vestibular-evoked myogenic potentials and a standard electronystagmography test battery. In the present study, the entire subject population assessed showed hypofunctional caloric responses and absent VEMPs. Two out of the three subjects were asymptomatic of vestibular dysfunction. On the clinical tests of stability, two subjects showed deviations to the right, while one subject performed normally. Thus, the present study indicates a possible involvement of peripheral vestibular nerve involvement in individuals with auditory neuropathy.