“Extra-Dural Anterior Clinoidectomy through the Lateral Supraorbital Approach: Surgical Anatomy and Initial Clinical Experience”

Background: Reduced invasiveness is a continuous trend in skull base surgery while standard skull base approaches still offer substantial advantages in selected cases. The lateral supraorbital approach is an increasingly used and less invasive alternative to pterional craniotomy, while the extradural anterior clinoidectomy (EAC) remains a standardized extension of the pterional craniotomy for the surgery of vascular and tumor lesions involving or in the vicinity of the anterior clinoid process (APC).

Objective: To describe a less invasive approach for EAC, through a modification of the lateral supraorbital craniotomy (LSO).

Method: A standard LSO craniotomy is done through an eybrow incision or a short fronto-temporal incision behind the hairline. The sphenoid wing is then drilled from the frontal inner side of the craniotomy exposing the superior and sylvian aspect of the temporal lobe without resection of the temporal bone and without a lateral temporal exposure. After the supero-lateral bony edge of the SOF is exposed and opened, the meningo-orbital dural fold is sectioned allowing stripping of the temporal dura from the lateral wall of the cavernous sinus and the inferior aspect of the APC. After unroofing of the optic canal, the APC is drilled and resected with standard technique. The optic strut is further removed, fully exposing the clinoidal segment of the ICA. Intradural steps are then taken according to the specific pathology. Our preliminary clinical experience with this technique includes 5 cases: 2 anterior clinoidal meningiomas, one orbital apex abscess, one mesio-temporal hematoma from a cavernous malformation and one carotido-ophtalmic aneurysm.

Results: There were no intraprocedural complications or manoeuvrability difficulties. One patient with a temporomesial hematoma from a cavernous malformation developed partial third nerve palsy. There was no visual acuity or visual field deterioration. No other approach related complications were noted. The cosmetic results were good with no significant atrophy of the temporal muscle and no palsy of the frontalis branch of the facial nerve.

Conclusion: A modified extradural anterior clinoidectomy can be safely achieved through a lateral supra-orbital approach. This ads a useful skull base technique to a less invasive craniotomy that can be used for intradural vascular and neoplastic lesions in the antero-lateral skull base and orbital apex.