Evaluation of contralateral acoustic brain stem reaction in patients with pontocerebellar angle tumors.

Contralateral acoustic brain stem response (ABR) waveforms were analyzed in 63 subjects with tumors of the pontocerebellar angle. The tumors were diagnosed by CT and the diagnoses were surgically confirmed. According to the latency changes and amplitude sizes, the ABR waveforms were classified into four types (O, A, B and C). All tumors were separated into groups (depending on size), and into subgroups (depending on type). Contralateral ABR was found to be affected by tumors greater than 20 mm, and significantly more often by neuroma than by other tumors (significance level 5%).