• Ryojo Akagami, Charles C J Dong, and Brian D Westerberg.
• Division of Neurosurgery, Department of Surgery, Vancouver General Hospital, Vancouver Coastal Health Research Institute, University of British Columbia, Vancouver, British Columbia, Canada. rakagami@vanhosp.bc.ca
• Neurosurgery. 2005 Jul 1; 57 (1 Suppl): 78-85; discussion 78-85.

ObjectiveTo describe a novel monitoring technique that allows "functional" assessment of cranial nerve continuity during cranial base surgery.MethodsFacial motor evoked potentials (MEP) in 71 consecutive patients were obtained by localized transcranial electrical stimulation in all patients requiring facial nerve monitoring during the period from November 2002 to August 2004. With transcranial electrical stimulation localized to the contralateral cortex, facial nerve MEPs are obtained through stimulation of more proximal intracranial structures.ResultsLogistic regression revealed that the final-to-baseline facial MEP ratio predicted satisfactory (House-Brackmann Grade 1 and 2 function) immediate postoperative facial function (0.005 > P > 0.0005). Contingency table analysis showed high correlation (chi2, P < or = 2 x 10(8)) and acceptable test characteristics using a 50% final-to-baseline MEP ratio.ConclusionFacial nerve MEPs recorded intraoperatively during cranial base surgery using the proposed technique predicts immediate postoperative facial nerve outcome. This technique can also be used to monitor other motor cranial nerves in cranial base surgery.

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