TECHNICAL ASPECTS OF INTRAOPERATIVE MONITORING OF LOWER CRANIAL NERVEFUNCTION

The efficacy of monitoring facial nerve activity in decreasing long-te rm morbidity has promoted an interest in monitoring other at-risk cran ial nerves during procedures that involve manipulation of the basal cr anial nerves. This presentation details practical techniques for monit oring the lower cranial nerves, which have been experientially develop ed over the past 9 years. Emphasis is placed on the selection of elect rodes and procedural changes required for reliable and safe stimulatio n of the basal cranial nerves. Either paired hook-wire or tethered nee dle electrodes can be used for monitoring glossopharyngeal, accessory, and hypoglossal nerve function. Several options for monitoring vagus nerve function are discussed. Of these, the transoral placement of pai red hook-wire electrodes remains the most reliable, cost-effective, an d least morbid technique. Electrical stimulation of the glossopharynge al and vagus nerves carries the risk of unanticipated, potentially irr eversible disturbances in cardiovascular function. Guidelines for type and optimal placement of stimulating electrodes and recommended inten sity levels to prevent unfavorable reactions are presented.