Abstract
An alternative technique for the continuous monitoring of the facial nerve, monopolar
recording of facial nerve antidromic potentials (FNAPs), on 10 subjects undergoing
retrosigmoid vestibular neurectomy for Meniere's disease is described. To elicit FNAPs
bipolar electrical stimulation of the marginalis mandibulae was performed. Stimulus
intensity ranged from 0 to 10 mA with a delivery rate of 7/second. Antidromic potentials
were recorded with a silver wire monopolar electrode positioned intracranially on
the proximal portion (root entry zone) of the acoustic-facial bundle. Bipolar recordings
with two silver electrodes were also performed from different nerves in the cerebellopontine
angle to define the specific origin of the action potentials. FNAP. amplitude increased
as a function of stimulus intensity. The average latency was 3.35 milliseconds (range
3.0 to 3.7 ms). Action potentials recorded intracranially during electrical stimulation
of the marginal nerve originated specifically from the facial nerve. FNAP recording
is therefore a promising technique for the continuous intraoperative monitoring of
the facial nerve during cerebellopontine angle surgery.
