Pre -vs. Post-Anterior Clinoidectomy Measurements of the Optic Nerve, Internal Carotid Artery, and Optico-Carotid Triangle: A Cadaveric Morphometric Study

ABSTRACT

Anterior clinoid process is a small bony structure but it is very important regarding its location and relationships with neighboring neurovascular, dural, and bony structures. Removal of this process has been used in various modification of standard pterional approach. The authors have speculated how much expansion of operative window could be obtained with anterior clinoidectomy, so we measured the lengths of optic nerve, internal carotid artery, and the length and width of optico-carotid triangle(OCT) before and after extradural anterior clinoidectomy 17 times in 10 cadaveric heads. This procedure provided about two fold increase in the length of optic nerve and OCT, and over three fold expansion in the width of OCT. The results indicate that the addition of this relatively simple and easy procedure to standard approach makes the operative field more comfortable and safe than expected. We believe this procedure can be used routinely with or without combination of wide skull base exposure in cases of such lesions as belows 1) lesions causing optic nerve or chiasmatic compression, 2) lesions encircling/covering the optic nerve and internal carotid artery, 3) lesions arising from or extending into the optic canal, orbital apex, and paraclinoid region, 4) suprasellar/parasellar lesions with limited operative windows(e.g. prefixed chiasm, infra-optic or subchiasmatic locations or adherence).