Unusual Third Head of the Sternocleidomastoid Muscle from the Investing Layer of Cervical Fascia

the abnormal origin, presence of additional head and layered arrangement of fibers are the reported variations of sternocleidomastoid muscle in the past. in the present case we report a rare unusual origin of third head of the sternocleidomastoid muscle in a 60 year-old male cadaver. this additional head originated from the investing layer of cervical fascia in the roof of the subclavian triangle close to the clavicle and traversed obliquely upward, forward and fused with clavicular head. the insertion and nerve supply of the muscle was found to be normal.