Neurophysiologic monitoring during cranial base surgery.

The last decade has seen a rapid growth in surgical techniques directed at resection of skull base tumors. Lesions that were previously inoperable can now be resected either partially or in some cases completely. The morbidity in these procedures has diminished with increased surgical experience. Additional aids to successful surgical resection include intraoperative neurophysiologic monitoring techniques. The following text outlines methods of monitoring cranial nerve and brain function in a manner that is directly relevant to cranial base surgery in which so many structures are potentially at risk. These techniques permit the identification of nerves obscured by tumor before they may be inadvertently damaged, the repeated confirmation during tumor resection that a nerve is still functional, and infer the state of brain and brainstem function during the course of long surgical procedures to help signal vascular compromise, or the effects of brain retraction. These techniques can only help to enhance the safety of the long and complex procedures required for successful resection of tumors of the cranial base.