title: Localizing retrocochlear hearing loss.
abstract: OBJECTIVE
  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 localised 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.
authors.affiliation: Department of Otolaryngology, University of Pittsburgh School of Medicine, Pennsylvania, USA.
authors.forename: B E
authors.initials: BE
authors.lastname: Hirsch
authors.forename: J D
authors.initials: JD
authors.lastname: Durrant
authors.forename: S
authors.initials: S
authors.lastname: Yetiser
authors.forename: D B
authors.initials: DB
authors.lastname: Kamerer
authors.forename: W H
authors.initials: WH
authors.lastname: Martin
mesh_terms: D000328:Adult; D001300:Audiometry, Evoked Response; D003051:Cochlea / Q000503:physiopathology*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007245:Inferior Colliculi / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D013063:Speech Discrimination Tests