Extracranial internal carotid artery: anatomical variations in asymptomatic patients.

The anatomical variations of internal carotid artery (ICA) are mostly asymptomatic, thus being disregarded and only incidentally diagnosed, with very few symptomatic patients. The awareness of these anomalies is crucial to solve the differential with other neck lesions, preventing accidental injuries during neck surgery. Therefore, the aim of our study is to estimate the prevalence of ICA anomalies, using magnetic resonance angiography (MRA) and computed tomography angiography (CTA). 253 patients underwent head and neck MRA and CTA examinations, with multiplanar and volumetric reformations. For each set of images, the following items were investigated: origin, development, course, persistence of embryonic vessels and anomalous origin of collateral branches. In our series, ICA arose from the bifurcation of the common carotid artery at the level of: C4 in 303 hemi-necks (59.9 %); C3 in 98 hemi-necks (19.3 %); C5 in 57 hemi-necks (11.3 %); C2 in 48 hemi-necks (9.5 %). ICA kinking and/or coiling was found in 105 hemi-necks, and location variation of ICA (reversed-type) in two hemi-necks. In just one case the origin of the ascending pharyngeal artery was from ICA (0.2 %), while an anomalous persistence of the proatlantal artery was noticed in three cases (0.6 %). CTA and MRA showed similar accuracy in detecting ICA anomalies.