Angiographic Characterization of the External Carotid Artery: Special Attention to Variations in Branching Patterns.

Knowledge of branching patterns of external carotid artery (ECA) is essential for planning and execution of head and neck surgeries. Digital subtraction angiography (DSA) images of 532 ECAs from 302 consecutive patients were retrospectively evaluated. We classify the branch variants of ECA into three types, simply based on the number of branches arising close together. Type A, Type B, and Type C variants are defined as two, three, and four or more branches of ECAs arising at a common point from the proximal ECA, respectively. In this classification, the distal ECA was counted as one branch. Of 532 ECAs, Type A was found in 344 ECAs (64.6%) of 237 patients (78.5%), Type B in 134 ECAs (25.2%) of 110 patients (36.4%), and Type C in 54 ECAs (10.2%) of 49 patients (16.2%). The distance from the common carotid artery (CCA) bifurcation to the first branch of ECA with Type C was 14.7 ± 6.6 mm; its distance is shorter compared with Type A (21.8 ± 15.6 mm) and Type B (20.6 ± 8.9 mm) (P < 0.05). The position of CCA bifurcation with Type C was detected at the third-fourth junction cervical vertebral level or higher in 52 of 54 ECAs (96.3%), significantly higher than those of the other types (P < 0.05). In conclusion, Type C ECA has aggregated vessels with short distance from CCA and high position of CCA bifurcation. Type C ECA is not uncommon; thus, special consideration should be paid to avoid complications during surgeries.