The Sternocleidomastoid Muscle
The sternocleidomastoid muscle is located in the neck. It acts to flex and rotate the head. It is given the name sternocleidomastoid because it attaches to the sternum (sterno-), the clavicle (cleido-), and the mastoid process of the temporal bone of the skull. It is also called the sternomastoid muscle.
The sternocleidomastoid is a complex muscle that can cause mild to severe neck pain. Often, neck discomfort is mistaken for a headache. Looking upward or reading in bed for extended periods can cause the sternocleidomastoid muscle to strain. Resting the head and mild stretching of the neck are the best treatments for a strained sternocleidomastoid muscle.