Endoscopic Transorbital Anterior Clinoidectomy: Surgical Anatomy and Step-wise Technique

BACKGROUND AND OBJECTIVES: Anterior clinoidectomy is a cornerstone technique for skull base and vascular neurosurgery. Enabling this procedure to be performed endoscopically through the orbit expands the transorbital corridor and offers a minimally invasive alternative to craniotomy. We provide a step-by-step description of endoscopic transorbital anterior clinoidectomy based on cadaveric dissection along with a critical analysis of the technique, including its potential applications, advantages, and limitations. We then demonstrate the clinical application of this approach in a 67-year-old patient undergone resection of an anterior clinoid process (ACP) and lateral wall cavernous sinus meningioma. METHODS: We conducted this procedure on 3 cadaveric heads, totaling 5 approaches, using 4-mm diameter and 275-mm length Karl Storz endoscopes with 0° and 30° viewing angles. A high-speed drill was used to access the middle and anterior fossae, and to remove the lesser sphenoid wing. Subsequent steps included unroofing the optic canal, hollowing the ACP, drilling the optic strut, and removing the ACP. This approach was then video recorded during resection of an anterior clinoid meningioma. RESULTS: In all 5 cadaver approaches, the ACP was removed without injury to the optic nerve or carotid artery. Although unroofing of the optic canal was executed in a confined space, optic strut drilling was performed under direct visualization, ensuring the safety of the optic nerve and carotid artery. In the clinical case, gross total tumor resection was achieved in the ACP, with some residual tumor within the cavernous sinus, resulting in no complications, postoperative improvement in vision, and patient satisfaction. CONCLUSION: Anterior clinoidectomy is essential for skull base and vascular neurosurgery with applications including tumor resection and optic nerve decompression. Our cadaver investigations study demonstrate that anterior clinoidectomy can be safely executed by an endoscopic transorbital approach, which is further demonstrated in a clinical case.