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Electrophysiology of Extraocular Cranial Nerves: Oculomotor, Trochlear, and Abducens Nerve

Hariharan, Praveen*; Balzer, Jeffery, R.*; Anetakis, Katherine*; Crammond, Donald, J.*; Thirumala, Parthasarathy, D.*,†

Journal of Clinical Neurophysiology: January 2018 - Volume 35 - Issue 1 - p 11–15
doi: 10.1097/WNP.0000000000000417
Invited Review

Summary: The utility of extraocular cranial nerve electrophysiologic recordings lies primarily in the operating room during skull base surgeries. Surgical manipulation during skull base surgeries poses a risk of injury to multiple cranial nerves, including those innervating extraocular muscles. Because tumors distort normal anatomic relationships, it becomes particularly challenging to identify cranial nerve structures. Studies have reported the benefits of using intraoperative spontaneous electromyographic recordings and compound muscle action potentials evoked by electrical stimulation in preventing postoperative neurologic deficits. Apart from surgical applications, electromyography of extraocular muscles has also been used to guide botulinum toxin injections in patients with strabismus and as an adjuvant diagnostic test in myasthenia gravis. In this article, we briefly review the rationale, current available techniques to monitor extraocular cranial nerves, technical difficulties, clinical and surgical applications, as well as future directions for research.

Departments of *Neurological Surgery and

Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, U.S.A.

Address correspondence and reprint requests to Parthasarathy D. Thirumala, MD, MS, Department of Neurological Surgery, Center for Clinical Neurophysiology, UPMC Presbyterian-Suite B-400, 200 Lothrop St, Pittsburgh, PA 15213, U.S.A.; e-mail: thirumalapd@upmc.edu.

The authors have no funding or conflicts of interest to disclose.

© 2018 by the American Clinical Neurophysiology Society