Microsurgical anatomy and variations of the anterior clinoid process

The aim of this study was to better define the microsurgical anatomy of the supra/parasellar region and describe variations of the anterior clinoid process (ACP).

Fifteen formalin-fixed cadaver heads and 25 dry skulls were used to define the microsurgical anatomy of the ACP and related structures. The presence of the caroticoclinoid foramen (CaCF) as well as other relevant measurements were all noted. Radiological examination of the CaCF was also demonstrated on dry skulls.

Interosseous bridges, which form between the anterior and middle clinoid processes or connect all three (anterior, middle and posterior) clinoid processes, were found in 30% of the specimens. The average basal width, length and thickness of the ACP were 7.3 mm, 9.7 mm and 5.4 mm, respectively. Length of the optic nerve (ON) up to the falciform ligament (FL) was 10.9 mm; length of the ON under the FL was 2.7 mm; length of ON after removal of the ACP and unroofing the optic canal was 21.1 mm.

This study contributes to the relationship of important vascular, neural, bone and dural layers of this region and also demonstrates the variations of ACP by means of microsurgical dissections and radiological examinations.