Intraoperative Monitoring (IOM) O-IM001. Intraoperative hypoglossal nerve mapping during carotid endarterectomy

Abstract

Introduction . Hypoglossal nerve deficit is a possible complication caused by carotid endarterectomy (CEA). The accidental injury of the hypoglossal nerve during surgery is one of the major reasons for permanent hypoglossal nerve palsy. In this study, we investigated the usefulness of intraoperative mapping of the hypoglossal nerve to identify this nerve during CEA. Methods . A total of consecutive patients who underwent CEA for the treatment of symptomatic or asymptomatic carotid artery stenosis were studied. A hand-held probe was used to detect the hypoglossal nerve in the operative field, and the tongue motor evoked potentials (MEPs) were recorded. Results . The tongue MEPs were obtained in all the patients. The invisible hypoglossal nerve was successfully identified without any difficulty when the internal carotid artery was exposed. Intraoperative mapping was particularly useful for identifying the hypoglossal nerve when the hypoglossal nerve passed beneath the posterior belly of the digastric muscle. MEPs were also elicited when the ansa cervicalis was stimulated, although the resulting amplitudes were much smaller than those obtained by direct stimulation of the hypoglossal nerve. Postoperatively, none of the patients presented with permanent hypoglossal nerve palsy, although one patient exhibited transient minor hypoglossal nerve paresis. Conclusion . Intraoperative hypoglossal nerve mapping enabled us to locate the invisible hypoglossal nerve during the exposure of the internal carotid artery accurately without retracting the posterior belly of the digastric muscle and other tissues in the vicinity of the internal carotid artery.