Localizing retrocochlear hearing loss

Purpose: The origin of acute/sudden hearing loss is multifactorial. The association of vestibular symptoms does not necessarily isolate the pathologic condition to the inner ear. The audiogram provides a screen for differentiating conductive from sensorineural loss but often fails to provide more localizing information. Methods: Three unusual patients with a variety of retrocochlear presentations of hearing loss are presented. Along with conventional auditory brainstem response (ABR) testing, newer auditory tests, including otoacoustic emissions and three-dimensional ABR analysis, can facilitate site-of-lesion testing. Magnetic resonance imaging (MRI) also provides graphic documentation for sources of retrocochlear hearing loss. Results: One patient had gamma-knife treatment of an arteriovenous malformation, incurring a localized lesion to the inferior colliculus contralateral to the side of hearing loss. This effectively eliminated wave V as confirmed by three-dimensional ABR analysis. A second patient with human immunodeficiency virus developed sudden complete hearing loss with retained otoacoustic emissions, confirming a retrocochlear lesion. A third patient with acute otitis media with sudden hearing loss and vertigo had an abnormal ABR and 'mass lesion' on MRI. Hearing subsequently returned to normal, as did a repeated scan. Conclusions: The unique aspects of each case of retrocochlear hearing loss and the applied auditory electrophysiologic tests are reviewed.