Intraoperative monitoring of cranial nerves

Intraoperative monitoring of cranial nerves is performed to minimize postoperative cranial nerve dysfunction. The authors performed electrophysiological monitoring of motor cranial nerves with an NIM 2 unit from Xomed Treace and a patient multiplexer developed in their department. This multiplexer allows the simultaneous monitoring of four cranial nerves and is additionally equipped with a bipolar stimulation mode. This intraoperative monitoring was employed during 102 skul: base operations. Of these 102 operations, 44 were acoustic neuroma removals using a translabyrinthine approach and 36 using a middle fossa approach. Various operations including removal of jugular foramen tumors and infratemporal fossa tumors were performed in the remaining 22 patients. The facial nerve, being the most frequently monitored nerve, was evaluated both pre-and intraoperatively. Electrophysiological data were evaluated with respect to their predictive value for postoperative facial nerve function. The relative percentage decrease in amplitude of the EMG after resection compared to that observed before surgery seems to be of some predictive value for postoperative facial nerve function. A 50-60% decrease or more is associated with an increase in the House classification. Intraoperative monitoring is a useful tool in skul: base surgery, allowing for safer and faster identification of motor nerves in pathological anatomical conditions. It allows the surgeon a degree of comfort by providing immediate information regarding the status of the nerve. It may also improve postoperative nerve function and shorten operating time. Additionally, neuromonitoring provides some information about expected postoperative facial nerve function.