Acoustic neuroma: results of brain stem evoked response audiometry.

Brain stem evoked response (BER) audiometry presents abnormal findings in patients with acoustic neuromas. The test involves averaging of recordings at the vertex as sound-triggered nerve impulses travel from the cochlea to the brain stem. From the time the sound stimulus arrives at the cochlea until it reaches the first major brain stem synapse (within 10 milliseconds), five major waves have been identified as typical of normal averaged responses. Abnormality in the cochlea or eighth nerve causes specific changes in pattern, primarily in wave latency. These latency shifts can be used to predict the site of the lesion. In evaluating 17 lesions of the cerebellopontine angle, BER audiometry was accurate in the diagnosis of all of the tumors. This diagnostic tool should play a prominent role when acoustic tumor is suspected.