Neurophysiological Identification of Cranial Nerves During Endoscopic Endonasal Surgery of Skull Base Tumors: Pilot Study Technical Report

INTRODUCTION: Intraoperative identification of cranial nerves is crucial for safe surgery of skull base tumors. Currently, only a small number of published papers describe the technique of trigger electromyography (t-EMG) in endoscopic endonasal removal of such tumors. OBJECTIVE: To assess the effectiveness of t-EMG in preventing intraoperative cranial nerve damage in endoscopic endonasal surgery of skull base tumors. MATERIALS AND METHODS: Nine patients were operated on using the endoscopic endonasal approach within a 1-year period. The tumors included large skull base chordomas and trigeminal neurinomas localized in the cavernous sinus. During the surgical process, cranial nerve identification was carried out using monopolar and bipolar t-EMG methods. Assessment of cranial nerve functional activity was conducted both before and after tumor removal. RESULTS: We mapped 17 nerves in 9 patients. Third, fifth, and sixth cranial nerves were identified intraoperatively. There were no cases of postoperative functional impairment of the mapped cranial nerves. In one case we were unable to get an intraoperative response from the fourth cranial nerve and observed its postoperative transient plegia (the function was normal before surgery). CONCLUSION: t-EMG allows surgeons to control the safety of cranial nerves both during and after skull base tumor removal.