The contralateral effects of large tumors on brain stem auditory evoked potentials.

Brain stem auditory evoked potential (BAEP) testing has been demonstrated to be a useful diagnostic tool in the presence of severe or complete sensorineural hearing loss. From a series of 38 patients with tumors in the vicinity of the VIIIth nerve, 13 patients with tumors larger than 2 cm had abnormal BAEP results contralateral to the involved side. The abnormalities observed on the noninvolved side included prolonged peak latencies, reduced amplitudes, poor wave shape and poor response stability. The significance of these findings is twofold: 1. Large tumors may disrupt BAEP test results on the side contralateral to the lesions, 2. Important information may be obtained on patients having complete sensorineural hearing loss on the involved side.