Facial vein draining into external jugular vein in humans: its variations, phylogenetic retention and clinical relevance

The superficial veins, especially the external jugular vein (EJV), are increasingly being utilized for cannulation to conduct diagnostic procedures or intravenous therapies. Ultrasound-guided venipuncture is a viable possibility in cases of variations in the patterns of superficial veins, and their knowledge is also important for surgeons doing reconstructive surgery. This study was done on 89 dissected adult cadavers (178 sides) and variations in patterns of termination of the facial vein (FV) into the EJV were studied. The FV in 16 sides (9%) was found to drain into the EJV, in two main patterns: type I and type II. Type I had the FV draining into the EJV with varying degrees of obliquity in a Y-shaped (6 cases, 37.5%), U-shaped (3 cases, 18.7%), tuning-fork-shaped (2 cases, 12.5%) or N-shaped (1 case, 6.2%) pattern. Type II showed an inverted A-shaped pattern (2 cases, 12.5%) or a stepladder-shaped pattern (2 cases, 12.5%) depending on the presence of one or more connecting conduits between the FV and EJV respectively. In Macaca mulatta (rhesus monkey) a pair of vertically disposed, subcutaneous veins placed nearly side by side and of equal caliber were seen on each side of the neck. The lateral vein was the EJV while the medial one took the course of the FV in the upper oblique segment and ran parallel to the EJV in the lower segment over the sternocleidomastoid, with one or two transverse communications. The anomalous patterns found in our study could be explained in terms of the regression and retention of various parts of the veins found in the rhesus monkey, or the drainage pattern found in horse, ox and dog, where the vein from the face drain into the external jugular vein, the internal jugular vein being either absent or a small vessel accompanying the carotid artery.