Variation in the branching pattern of the four major caudal vessels emerging from the external carotid artery

The branching pattern of vessels emerging from the external carotid artery (ECA) displays considerable variation. Knowledge of this variation is of particular interest to clinicians. There are few reports in the literature assessing these differences with regard to sex and sidedness (i.e., branching patterns of the right vs. left neck). The objective of this study was to assess the origin of the four primary caudal branches of the external carotid artery: the superior thyroid (STA), lingual (LA), facial (FA), and occipital (OA) arteries, in addition to the level of common carotid artery bifurcation (CB), with regard to sex, and side. Additionally, variation within this study population was considered in the context of global variation. Seventy-nine cadavers (37 male, 42 female) were studied (71 right necks, 68 left necks). All carotid bifurcations were observed cranial to a midpoint located centrally between the mastoid process and the suprasternal notch. No significant difference was found for the mean distance of CB from the midpoint with regard to sex (p = 0.70) or side (p = 0.75). The STA on the right side emerged from the CB/ECA more frequently than it did from the common carotid artery (CCA) (67% and 31%, respectively); however, on the left side, the STA emerged more frequently from the CCA than from the CB/ECA (57% and 43%, respectively) (p = 0.003). The STA also exhibited a significantly longer distance from CB on the left than on the right (p = 0.006). The LA and FA arose individually more frequently than from a common trunk (79% and 21%, respectively). The OA emerged below the origin of the FA more frequently than at/above the FA (55% and 44%, respectively). With regard to sex, branching pattern variation was similar for the vessels studied. No considerable variation was noted between this populations and other ethnic populations for STA or LA/FA origin locations. Variation in ECA branching pattern is substantial with respect to side but not sex or ethnicity. This information may assist clinicians in preventing iatrogenic arterial injury by creating awareness of differential ECA branching pattern between neck sides, and may also allow for decreased incision lengths during surgical intervention to the carotid arterial system