Unilateral duplicated abducens nerve coursing through both the sphenopetroclival venous gulf and cavernous sinus: a case report.

In this anatomy report, we describe the first case of abducens nerve duplication limited to the sphenopetroclival venous gulf and the cavernous sinus. The objective point of division of the two duplicated roots was localized at the gulfar face of the dural porus, just distal to the unique cisternal trunk of the abducens nerve, as it pierced the petroclival dural mater. In the gulfar segment, both roots traveled through a variant of Dorello's canal called the "petrosphenoidal canal" and remained separated through the posterior half of the cavernous sinus. Both roots finally fused in the anterior half of the cavernous sinus to innervate the lateral rectus muscle as a single trunk. Although many variants of the abducens nerve have been reported over the recent decades, this anatomic variation has never been previously described and enriches the continuum of abducens nerve variations reported in the literature data. Awareness of this variation is crucial for neurosurgeons, especially during clival or petrosal surgical approaches used for resection of skull base chordomas.