The enigmatic clival canal: Anatomy and clinical significance

Purpose: There is scant and conflicting literature regarding bony canals of the clivus. To date, only osteological observations of dry skulls have been made of such structures and multiple hypotheses exist regarding the etiology of these entities and whether or not they represent normal variations or pathology. The present study was performed to elucidate, specifically, clival canals of the occipital portion of the clivus. Methods: One hundred dry skulls (80 adult and 20 children) and 47 adult cadavers were included, and the superior and inferior surfaces of their clivus were inspected for bony defects/canals. When identified, the canals were measured and their potential contents removed. The contents of the canals in these cadaveric specimens were submitted for histological analysis. Results: A canal of the clivus was identified in 5% of dry specimens and in 6.4% of cadaveric specimens. One diagonal and five more or less vertical canals were found. One canal was observed to have a single opening and one canal was found to have three openings. For the cadaveric canals, histology of the contents revealed no pituitary or notochordal tissue with only vascular anatomy consistent with veins. These venous structures appeared to connect parts of the basilar venous plexus. Conclusions: Based on our study, which is the first of its kind, such canals of the occipital portion of the clivus should not be mistaken for pathology and represent simple vascular channels.