Sternomastoid muscle injury symptoms

Updated April 17, 2017

Injuries to the sternocleidomastoid (SCM) muscle reduce range of motion in the neck and head. Nerves, which extend from the first to the fourth cervical vertebrae, are under the SCM muscle. Constriction of these nerves to the brain can produce dizziness, allergies, and headaches. Nerves to the shoulder under the SCM, if constricted, effect the shoulder, arms, and breathing. Spasms of the SCM muscle can impair hearing, sight and speech.


The sternocleidomastoid muscle extends from the skull behind the ear to the middle of the chest to the collar bone or clavicle. The SCM muscle is narrow, but thick in the middle and wide at each end. Each end resembles the base of a triangle with the vertices of the triangles at the middle of the muscle. The muscle vertically covers the side of the neck.


The sternocleidomastoid muscle tilts and rotates the head to the opposite side of the body. Acting with other muscles it flexes the neck and raises the sternum during breathing. The SCM muscle is attached to the neck, shoulder and chest.

The cervical plexus of nerves from the first through fourth cervical vertebrae merge and communicate then branch into deep motor and superficial sensory nerves under the SCM muscle. The deep motor branch energises neck muscles and muscles from the neck to the shoulder. The sensory branch responds to the neck, shoulder and upper chest.

Spinal Accessory Nerve

The spinal accessory nerve, leaving the base of the skull, energises the SCM muscle and the trapezius muscle. A pinched spinal accessory nerve restricts raising the arm above the head laterally and causes shoulder discomfort from stress to the muscles and ligaments that compensate for a weak trapezius muscle.

The greater auricular nerve below the SCM muscle is a few millimetres from the spinal accessory nerve. It branches to the parotid (salivary) gland area, the posterior region of the ear and connects to the facial nerve.

Chiropractic Relief

Relief from sternocleidomastoid injury can be found through chiropractic adjustments to improve function and reduce symptoms. Chiropractic adjustment is forcing the joints further than the joint normally moves to realign vertebrae, relax muscles and uncover pinched nerves.

The chiropractor applies muscle stimulation and ultrasound to stretch or relax tense muscles. The chiropractor recommends exercises to improve the functioning of the SCM muscle.

Recovery may take years. Muscle relaxants will help somewhat, but prolonged use of muscle relaxants weakens the normal muscle tension necessary to support and move the head.


Biofeedback from a computer with electromagnetic pads on the head, shoulders, chest and extremities monitors muscle tension, body temperature, pulse and electrocardio output. Turning out lights reduces muscle tension. Progressive relaxation technique is systematically tensing and relaxing groups of muscles to improve functioning. Deep breathing from the diaphragm, as opposed to shallow breathing relaxes the shoulders.

Imagery relaxation with pre-hypnotic tapes deeply relaxes muscle tension through pre-hypnotic phrases. You will hear statements such as: Lovely lavender orchids. Time is yours. A marble staircase. You feel relaxed. At the end of the staircase, is a warm pool of water. The water is warm. The temperature is just right. Experiencing imagery relaxation can feel like floating on top of a pool of water.

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