The Topography and Variations of the Extra- and Intracranial Vessels

Abstract

The position of the internal carotid artery in relation to the external carotid artery can have many surgically important variations [2]. The internal carotid artery can lie lateral to the external carotid artery in 50% of cases (Plate 1), dorsal in 21% (Plate 2), dorsomedial in 18% (Plate 3), medial in 3% (Plate 4) or ventromedial in 9% (Plate 5). The internal carotid artery does not normally give off branches in the neck and only exceptionally gives rise to the ascending pharyngeal and the occipital arteries. Bryce et al. [1] have reported a case in which the left vertebral artery originated from the internal carotid artery 3 cm above the carotid bifurcation. Additionally, Kwak et al. [3] have described a case in which the posterior meningeal artery was found to originate from the extracranial part of the internal carotid artery (not represented).