The importance of the auditory evoked potential in acoustic neuromas.

Hearing loss, frequently with tinnitus, is the main symptom of acoustic neuromas (ANs), which compress the cochlear nerve and affect the cochlear blood supply. This vascular mechanism explains why atypical, fluctuating deafness, with audiometric features of retrocochlear involvement, may occur in this condition. An early diagnosis of ANs is essential for a good prognosis. Physicians should recognize the clinical signs of neurinomas, particularly in individuals aged just over 40 years; this is true even in cases of symmetrical sensorineural hearing loss. The brainstem auditory evoked potential (BAEP) is an objective, non-invasive method for a neurophysiological analysis of auditory pathways from the inner ear to the high brainstem. It is a short latency potential that generates a wave series (from I to VII) that appears within the first 10 ms after a sound stimulus is presented. These waves are generated due to the sequential activation of auditory pathway structures, and are picked up by electrodes placed on the skin.