Enhanced exposure of carotico-oculomotor triangle following extradural anterior clinoidectomy: A comparative anatomical study

Objective: To quantify and compare the carotico-oculomotor triangle (COT) area before and after extradural anterior clinoidectomy (AC). Methods: Ten cadaveric heads were dissected bilaterally. Before and after an extradural. AC, the following points were measured: (1) the internal carotid artery (ICA) bifurcation to the tip of the anterior clinoid process (ACP) (A) and to the distal dural ring (A'), (2) the ICA bifurcation to the point where the oculomotor nerve becomes obscured by the tentorial fold (B) and to the porus oculomotoris after incision of the tentorial fold (B') and (3) the tip of the ACP to the point where the oculomotor nerve becomes obscured by the tentorial incisura (C) and from the distal. dural ring to the porus oculomotoris (C'). The area of the COT was calculated before and after AC (Delta ABC and Delta A'B'C', respectively). Results: The mean values were as follows: A: 9.15 +/- 0.93 mm, A': 13.45 +/- 0.82 mm; B: 7.80 +/- 1.24 mm, B': 9.90 +/- 1.21 mm; C: 7.15 +/- 0.99 min, C': 9.3 +/- 1.26 mm; Delta ABC: 26.26 +/- 16.05 mm(2), Delta A'B'C': 45.06 +/- 8.92 mm(2). Conclusions: Extradural AC enhances the exposure of the COT almost twofold. This increased exposure can be of significant help during resection of lesions of the parasellar and basilar apex regions.