Internal Jugular Vein Duplication: Anatomic Relationship With the Spinal Accessory Nerve.

Level II neck dissection is a commonly performed procedure in head and neck surgery. It carries the risk of injury to the spinal accessory nerve (SAN) and the internal jugular vein (IJV). Injury to any of these structures leads to increased intraoperative and postoperative complications and morbidity. Knowledge of the anatomic relation and possible variations from the norm is vital to decrease the morbidity of this frequently practiced procedure. This report describes 2 rare variations of the relation of the SAN to the IJV: 1) the IJV splitting with SAN passage through the IJV window and 2) the IJV splitting without SAN passage through the IJV window. Preoperative imaging and the pertinent literature regarding the variability in the relations of these structures are reviewed.