Endoscopic Extradural Anterior Clinoidectomy via Supraorbital Keyhole: A Cadaveric Study

BACKGROUND: Anterior clinoidectomy is an essential preliminary step for parasellar and pericavernous sinus surgery. Endoscopy is a widely accepted modality for neurosurgical strategies and is becoming more important in treating conditions involving the cranial base. OBJECTIVE: To determine the feasibility of endoscopic extradural anterior clinoidectomy via the supraorbital keyhole. METHODS: Eight fresh cadaver heads were studied using 4-mm, 0- and 30-degree rigid endoscopes to perform endoscopic extradural anterior clinoidectomy. We also evaluated a bony landmark for this technique in 36 dry craniums. RESULTS: An endoscope was introduced into the extradural space created via a supraorbital keyhole craniotomy. The periorbita and the duplication of the dura extending to the temporal lobe dura and periorbita were exposed by drilling. Anterior clinoidectomy proceeded using a diamond drill under endoscopic visualization without a dural incision. A submerged view with continuous irrigation through an endoscopic sheath maintained clear visibility while drilling. A small bony eminence at the transition between the sphenoid ridge and the anterior clinoid process, which is an anatomic landmark for endoscopic extradural anterior clinoidectomy, was identified in 57.4% of 36 adult dry craniums. CONCLUSION: The endoscopic extradural procedure can accomplish reliable anterior clinoidectomy under superb endoscopic visualization. This method would be applicable to parasellar and cavernous sinus surgery combined with keyhole or conventional craniotomy.