Abstract
Intraoperative monitoring of cranial nerves is performed to minimize postoperative
cranial nerve dysfunction. We performed electrophysiologic monitoring of motor cranial
nerves with a NIM 2 unit from Xomed Treace and a patient multiplexer developed in
our clinic. This multiplexer allows simultaneous monitoring of four cranial nerves
and is additionally equipped with a bipolar stimulation mode. This intraoperative
monitoring was used during 102 skull base operations. Of these, 44 operations were
acoustic neuroma removals by translabyrinthine approach and 36 by a middle fossa approach.
Various operations, including removal of tumors of the jugular foramen and the infratemporal
fossa, were performed in the remaining 22 patients. The facial nerve, being the most
frequently monitored nerve, was evaluated both preoperatively and intraoperatively.
Electrophysiologic data were evaluated with respect to their predictive value for
postoperative facial nerve function. The relative percent decrease in amplitude of
the electromyogram after resection compared to that observed before resection seems
to be of some predictive value for the postoperative facial nerve function. A 50 to
60% decrease or more is associated with an increase in the House classification. Intraoperative
monitoring is a useful tool in skull base surgery, allowing for safer and faster identification
of motor nerves in pathologic-anatomic 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.
