Sternocleidomastoid muscle
The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the accessory nerve.
Sternocleidomastoid
Motor: spinal accessory nerve
sensory: cervical plexus
Proprioceptive: ventral rami of C2-3
Unilaterally: contralateral cervical rotation, ipsilateral cervical flexion Bilaterally: cervical flexion, elevation of sternum and assists in forced inhalation.
musculus sternocleidomastoideus
Clinical significance[edit]
Examination of the sternocleidomastoid muscle forms part of the examination of the cranial nerves. It can be felt on each side of the neck when a person moves their head to the opposite side.[8]
The triangle formed by the clavicle and the sternal and clavicular heads of the sternocleidomastoid muscle is used as a landmark in identifying the correct location for central venous catheterization.
Contraction of the muscle gives rise to a condition called torticollis or wry neck, and this can have a number of causes. Torticollis gives the appearance of a tilted head on the side involved. Treatment involves physiotherapy exercises to stretch the involved muscle and strengthen the muscle on the opposite side of the neck. Congenital torticollis can have an unknown cause or result from birth trauma that gives rise to a mass or tumor that can be palpated within the muscle.