Merging the Paraclival ICA with the Bouthillier Classification

Background: The anatomy of the carotid artery has traditionally been understood in segments that correspond to the surrounding relevant anatomy. Our team was one of the first pioneers to define the transcranial segments of internal carotid artery in 1996. With the advent of endoscopic approaches a new term has been added to the carotid anatomy lexicon. This “paraclival” carotid has been used by many authors but a clear correlate to the transcranial anatomy has not been described. Methods: Two cadaveric specimens underwent both endoscopic and transcranial dissection. Two aneurysm clips were then used to mark the paraclival ICA. Results: Our dissection confirmed that from a transcranial approach, the proximal (inferior) clip was located just medial to the origin of the petrolingual ligament while the distal clip was placed just inferior to the posterior genu of the cavernous ICA. The two clips were therefore defining the lacerum segment and vertical portion of the cavernous segment ICA. Conclusion: Internal carotid artery plays a very important anatomical landmark in both endoscopic endonasal surgery and open transcranial procedure. Detail anatomical knowledge of ICA can guide the surgeon in endoscopic approach to the skull base. In this article, we present a transcranial correlation to the endoscopic definition of paraclival ICA.