Microsurgical anatomy of the oculomotor triangle and clinical application

Objective To describe anatomic details and landmarks of the oculomotor nerve triangle, and to investigate its clinical application for providing anatomical basis on protection in operation. Methods Ten consecutive vaso-perfused cadaveric heads (20 sides) were examined. Information was obtained about the size of the oculomotor triangle and its structural relationship. The results applied to 5 trigeminal neurinomas of the petroclival region, 5 meningiomas, 5 medial sphenoid ridge meningioma and 25 aneurysm of the posterior communicating artery. Results The oculomotor triangle is formed by the anterior petroclinoid ligament, posterior petroclinoid ligament and the interclinoid ligament. The oculomotor nerve penetrates cavernous by the center of the triangle. The distance between the entrance to the supraclinoid ICA (internal carotid artery) is 2-7 mm, averaged 5 mm. Outside the top adjacent to the anterior choroidal artery and at the top adjacent to the posterior communicating artery. The trochlear nerve enters the cavernous sinus from lateral-inferior to the oculomotor nerve. Among the 40 patients, there were 5 patients suffered from oculomotor nerve injury. 2 patients recovered during 3 months after operation. While other 3 patients did not recover. 2 in 35 patients suffered from oculomotor nerve injury after the operation and recovered in 3 months. Conclusions The anatomy of the oculomotor triangle is complex. The anterior petroclinoid ligament, posterior petroclinoid ligament and the interclinoid ligament are the good anatomy markers during the operation to identify the oculomotor nerve. It is important to observe and protect the oculomotor nerve in the part of saddle area, parasella and petrous apex.