Intraoperative neurophysiological monitoring and mapping during brain stem surgery: a modern approach

Although magnetic resonance imaging technology has contributed significantly to the surgical treatment of a variety of brain stem pathologies, it remains an inadequate tool in the prevention of intraoperatively induced brain stem neurological injury. We introduce a new approach to brain stem intraoperative neurophysiological monitoring that promises to diminish intraoperative morbidity to the motor system by the proper identification of exposed brain stem structures, before initial incision or during tumor removal. The approach comprises three intraoperative neurophysiological techniques: The first technique localizes the motor cranial nerve nuclei on the surgically exposed floor of the fourth ventricle. The second technique localizes the corticospinal tract within the cerebral peduncle. The third technique tests the functional integrity of the corticospinal tract through continuous monitoring and eliciting of the D waves (descending activity) from the electrically activated corticospinal tracts. Copyright (C) 2000 by W.B. Saunders Company.