Internal Jugular Vein Fenestration: An Intraoperative Finding Without a Radiological Clue.

A comprehensive understanding of the anatomical variations of the internal jugular vein (IJV) is essential to prevent inadvertent injuries during neck procedures, particularly neck dissection. In addition, its relationship with the spinal accessory nerve in the upper part of the neck is relatively variable. IJV fenestration refers to bifurcation of the vein with reunion proximal to the subclavian vein, whereas IJV duplication refers to continued branching till joining the subclavian vein separately. We report a case of a fenestrated IJV identified intraoperatively with the spinal accessory nerve passing laterally to both divisions.