Abstract
The feasibility and usefulness of intraoperative electromyographic monitoring of the
oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN IV) were
evaluated under conditions of partial neuromuscular blockade in 21 patients undergoing
skill base surgery. Intracranial electrical stimulation of each nerve was performed,
and compound muscle action potentials (CMAPs) were reconded from the inferior or superior
rectus muscle, the superior oblique muscle, and the lateral rectus muscle for monitoring
of CN III, IV, and VI, respectively. Partial neuromuscular blockade was achieved by
controlled infusion of vecuronium titrated to eliminate about 90% of the twitch response
of the abductor pollicis brevis to electrical stimulation of the median nerve. A total
of 30 cranial nerves were stimulated intraoperatively. Of these, 29 were successfully
monitored (19 CN III, 6 CN IV, 4 CN VI). A relationship was found between intraoperative
findings of cranial nerve monitoring, such as disappearance of response and increase
in latency and stimulus threshold during manipulation of a lesion, and the presence
of postoperative nerve deficits. We conclude that intraoperative electromyographic
monitoring of ocular motor nerves is feasible during partial neuromuscular blockade,
and that partial neuromuscular blockade does not affect the relationship between findings
of intraoperative monitoring and postoperative nerve function.
