Third head of sternocleidomastoid muscle

Abstract

During routine dissection in the neck region, a third head of sternocleidomastoid (SCM) muscle was found unilaterally in one cadaver and bilaterally in another cadaver. In both the cases third head was supplied by the spinal accessory nerve. SCM is most prominent muscle in the neck region which is used as important landmark during teaching living anatomy and gross anatomy of triangles of neck to students. As many important nerves and vessels are related to this key muscle of neck, any variation in relation to its origin, insertion and nerve supply attracts the attention of surgeons and anatomists. Embryological basis and clinical significance was discussed in these two cases of unilateral and bilateral presence of third head of SCM.

Keywords

• sternomastoid
• cleidomastiod
• neck muscle
• mastoid process