The purpose of this study was to determine whether monitoring of pharyngeal motor evoked potentials (PhMEPs) elicited by transcranial electrical stimulation during skull base tumor surgery might be useful for predicting postoperative swallowing deterioration.
The authors analyzed PhMEPs in 21 patients during 22 surgical procedures for the treatment of skull base tumors. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supramaximal stimuli (220–550 V). Pharyngeal MEPs were recorded from the posterior wall of the pharynx through a modified endotracheal tube. The correlation between the final/baseline PhMEP ratio and postoperative swallowing function was examined.
Postoperative swallowing function was significantly (p < 0.05), although not strongly (r = −0.47), correlated with the final/baseline PhMEP ratio. A PhMEP ratio < 50% was recorded during 4 of 22 procedures; in all 4 of these cases, the patients experienced postoperative deterioration of swallowing function. After 18 procedures, the PhMEP ratios remained > 50%; nevertheless, after 4 (22.2%) of these 18 procedures, patients showed deterioration of swallowing function.
Intraoperative PhMEP monitoring can be useful for predicting swallowing deterioration following skull base surgery, especially in patients with swallowing disturbances that are mainly due to reduction in the motor functions of the pharyngeal muscles.
Abbreviations used in this paper: CMAP = compound muscle action potential; MEP = motor evoked potential; PhMEP = pharyngeal MEP.
Address correspondence to: Masafumi Fukuda, M.D., Department of Neurosurgery, Brain Research Institute, University of Niigata, 1-757 Asahimachi-dori, Chuo-ku, Niigata City 951-8585, Japan. email: firstname.lastname@example.org.
Please include this information when citing this paper: published online December 9, 2011; DOI: 10.3171/2011.10.JNS111343.
DeMonteFWarfPAl-MeftyOIntraoperative monitoring of the lower cranial nerves during surgery of the jugular foramen and lower clivus. LoftusCMTraynelisVC: Intraoperative Monitoring Techniques in NeurosurgeryNew YorkMcGraw-Hill1994. 205–212
DongCCMacdonaldDBAkagamiRWesterbergBAlkhaniAKanaanI: Intraoperative facial motor evoked potential monitoring with transcranial electrical stimulation during skull base surgery. Clin Neurophysiol116:588–5962005
GrayeliABGuindiSKalamaridesMEl GaremHSmailMReyA: Four-channel electromyography of the facial nerve in vestibular schwannoma surgery: sensitivity and prognostic value for short-term facial function outcome. Otol Neurotol26:114–1202005
HermannMHellebartCFreissmuthM: Neuromonitoring in thyroid surgery: prospective evaluation of intraoperative electrophysiological responses for the prediction of recurrent laryngeal nerve injury. Ann Surg240:9–172004