CONTRALATERAL EVOKED BRAIN-STEM AUDITORY POTENTIALS AS AN INDICATOR OF INTRAOPERATIVE BRAIN-STEM MANIPULATION IN CEREBELLOPONTINE ANGLE TUMORS

Brainstem auditory evoked potentials (BAEP) were studied during operat ions to remove acoustic tumors using the retromastoid approach. BAEP w ere elicited from the side contralateral to the tumor, and changes in the latencies of peaks III and V of the BAEP were compared with change s in cardiovascular parameters throughout the operation. When the chan ges in the determined cardiovascular parameters were related to surgic al manipulations, the related changes in the latencies of peaks III an d V of the BAEP were more consistent than the changes in the cardiovas cular parameters and they tended to occur earlier than the changes not ed in the cardiovascular parameters.