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Alternative Sites for Intraoperative Monitoring of Cranial Nerves X and XII During Intracranial Surgeries

Holdefer, Robert N.; Kinney, Gregory A.; Robinson, Larry R.; Slimp, Jefferson C.

Journal of Clinical Neurophysiology: June 2013 - Volume 30 - Issue 3 - p 275–279
doi: 10.1097/WNP.0b013e3182933c2a
Original Research

Summary: During intracranial surgeries, cranial nerve (CN) X is most commonly monitored with electromyographic endotracheal tubes. Electrodes on these endotracheal tubes may be displaced from the vocal folds during positioning, and there is a learning curve for their correct placement. Cranial nerve XII is most commonly monitored with electrodes in the dorsum of the tongue, which are also prone to displacement because of their proximity to the endotracheal tube. A retrospective review was conducted of a consecutive series of 83 skull base surgeries using alternative sites for monitoring CN X and XII. On-going (spontaneous) and evoked electromyography (EMG) were obtained from the cricothyroid muscle for CN X and submental genioglossus for CN XII. Stimulation of CN X or XII evoked specific compound motor action potentials from these muscles, and well-defined on-going EMG was observed during tumor resection in the vicinity of CN X and XII. Volume-conducted responses from the adjacent platysma muscle during CN VII stimulation were identified by concomitant responses from the orbicularis oris and oculi. In conclusion, during skull base surgeries, CN X may be monitored with electrodes in the cricothyroid muscle and CN XII with electrodes in the submental genioglossus. These alternative sites are less prone to displacement of electrodes compared with the more commonly used EMG endotracheal tube and electrodes in the dorsum of the tongue. The cricothyroid muscle should not be used when the recurrent laryngeal nerve is at risk.

Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, Washington, U.S.A.

Address correspondence and reprint requests to Robert N. Holdefer, PhD, Department of Rehabilitation Medicine, University of Washington, Harborview Medical Center, 325 9th Avenue, Box 359740, Seattle, WA 98104-2499, U.S.A.; e-mail: holdefer@uw.edu.

© 2013 by the American Clinical Neurophysiology Society