Results: Accessory N after escaping from the skull base, mostly precedes the internal jugular vein (IJV) (62.5%), then crosses behind the posterior belly of digastric muscle, 5.39 ± 3.15 mm and 13.12 ± 3.34 mm from the anterior and posterior border of IJV; 3.74 ± 3.46 mm and 36.01 ± 7.53 mm from the posterior belly and tendon of digastric M Accessory N gives off one branch to the sternocleidomastoid muscle (SCM), then passes through the muscle in 60% of cases.