[A simplified method to monitor oculomotor nerve function in midbrain surgery: recordings of compound muscle action potentials by percutaneous superior orbital electrode].

We report a simple and easily-applicable method to intraoperatively monitor the oculomotor nerve and oculomotor nucleus in the brainstem. A needle electrode is inserted into the space just beneath the superior root of the orbit. With this superior orbital electrode, evoked compound muscle action potentials from the superior rectus and the levator palpebrae superioris muscles were recorded. The nuclei for these two muscles are located caudally in the midline of the midbrain. The responses from the superior orbital electrode, therefore, give the surgeons useful intraoperative guidance during surgery for pineal region tumors and midbrain gliomas.