A road map to the internal carotid artery in expanded endoscopic endonasal approaches to the ventral cranial base.
BACKGROUND
Injuring the internal carotid artery (ICA) is a feared complication of endoscopic endonasal approaches.


OBJECTIVE
To introduce a comprehensive ICA classification scheme pertinent to safe endoscopic endonasal cranial base surgery.


METHODS
Anatomic dissections were performed in 33 cadaveric specimens (bilateral). Anatomic correlations were analyzed.


RESULTS
Based on anatomic correlations, the ICA may be described as 6 distinct segments: (1) parapharyngeal (common carotid bifurcation to ICA foramen); (2) petrous (carotid canal to posterolateral aspect of foramen lacerum); (3) paraclival (posterolateral foramen lacerum to the superomedial aspect of the petrous apex); (4) parasellar (superomedial petrous apex to the proximal dural ring); (5) paraclinoid (from the proximal to the distal dural rings); and (6) intradural (distal ring to ICA bifurcation). Corresponding surgical landmarks included the Eustachian tube, the fossa of Rosenmüller, and levator veli palatini for the parapharyngeal segment; the vidian canal and V3 for the petrous segment; the fibrocartilage of foramen lacerum, foramen rotundum, maxillary strut, lingular process of the sphenoid bone, and paraclival protuberance for the paraclival segment; the sellar floor and petrous apex for the parasellar segment; and the medial and lateral opticocarotid and lateral tubercular recesses, as well as the distal osseous arch of the carotid sulcus for the paraclinoid segment.


CONCLUSIONS
The proposed endoscopic classification outlines key anatomic reference points independent of the vessel's geometry or the sinonasal pneumatization, thus serving as (1) a practical guide to navigate the ventral cranial base while avoiding injury to the ICA and (2) further foundation for a modular access system.
*Division of Neurosurgery, Department of Surgery, University of Ottawa, Ottawa, Ontario, Canada; Departments of ‡Neurosurgery and §Otolaryngology-Head and Neck Surgery, The Ohio State University, Columbus, Ohio; ¶Department of Otolaryngology, University of Ottawa, Ottawa, Ontario, Canada; ‖Aurora Neuroscience Innovation Institute, Aurora St. Luke's Medical Center, Milwaukee, Wisconsin.
Mohamed A
MA
Labib
Daniel M
DM
Prevedello
Ricardo
R
Carrau
Edward E
EE
Kerr
Cristian
C
Naudy
Hussam
H
Abou Al-Shaar
Martin
M
Corsten
Amin
A
Kassam
D059925:Anatomic Landmarks / Q000033:anatomy & histology*; D002102:Cadaver; D002343:Carotid Artery, Internal / Q000033:anatomy & histology*; D006801:Humans; D044583:Neuroendoscopy / Q000379:methods*; D019291:Skull Base / Q000098:blood supply / Q000601:surgery