The Abducens Nerve

Abstract

To the Editor: We read the article of Iaconetta et al.(1) describing the microscopic and endoscopic anatomy of the abducens nerve. The authors performed excellent work. They divided the abducens nerve into five segments, of which three are intracranial (cisternal, gulfar, cavernous) and two are orbital (fissural, intraconal). They stressed that the nerve courses in the cavernous sinus medially to the ophthalmic nerve and superiorly parallel to the petrolingual ligament (PLL). They added that the PLL is closely related to the medial surface of the dura and it covers both Meckel's cave and the ophthalmic branch of the trigeminal nerve with its sympathetic fibers. The PLL was meticulously inspected by us in a former study (2). The PLL is bow shaped and extends between the lingula of the sphenoid bone and the petrous apex. It has three parts: anterior tail, body, and posterior tail. The ligament is the posterior border of the cavernous sinus and lies under the junction of the maxillary and mandibular branches of the trigeminal nerve and the proximal part of the trigeminal root. The abducens nerve leaves the cavernous sinus at Dorello's canal through a triangle that was first described by our group (2,3). This triangle is constituted by the PLL, the petrosphenoidal ligament (Gruber's ligament), and the cavernous carotid artery. This means that the abducens nerve should not be superior to the PLL but inferior to it. On the other hand, the ophthalmic branch is anterior to the PLL. The abducens nerve may be stretched in this triangle as a result of various pathologies or increased intracranial pressure. Ibrahim M. Ziyal Tunçalp Özgen Ankara, Turkey