Surgical management of nonvascular lesions around the oculomotor nerve

Objective: Schwannomas originating from the oculomotor nerve are extremely rare. We report our experience in the management of oculomotor schwannomas and other lesions mimicking them, and discuss operative strategy for these rare tumors emphasizing oculomotor nerve preservation. Methods: The clinical records of our patients and all those reported in the literature focusing on oculomotor schwannomas were reviewed and analyzed. The clinical presentations, operative approaches, complications, and results were studied. Results: Between 1983 and 2010, six patients with primary oculomotor nerve lesions were treated. Three of them had schwannomas. Two others had pathologies that mimicked an oculomotor schwannoma and one was suspected as schwannoma. In the literature there were 55 previous cases of oculomotor schwannomas reported (surgical treated, 41 cases; observed, 9; gamma knife surgery treated, 2; autopsy, 3). Patients presented most commonly with diplopia, followed by headache and ptosis as initial symptoms. Out of 55 patients including the present 3 cases (3 autopsy cases were excluded), 30 patients (54.5%) finally developed oculomotor nerve palsy. Fifteen of 44 patients (34.1%) who underwent surgery developed persistent postoperative oculomotor palsy. Among them, 6 patients developed total palsy after surgery. Five of 12 patients (41.7%) who did not undergo surgery also developed oculomotor palsy. Oculomotor schwannomas most often grow its cisternal segment (48.3%) followed by intracavernous (39.6%) and cisternocavernous segments (12.1%). Conclusion: The microsurgical resection of oculomotor schwannomas carries a risk of worsening preoperative oculomotor nerve function; however, this is often transient. Considerable technical training and microanatomical knowledge of the region is required to optimize outcome.