Definition

1. Noun:
   • A major paired muscle in the neck: The sternocleidomastoid muscle is one of two thick, prominent muscles that run obliquely on each side of the neck. It originates from the sternum (breastbone) and clavicle (collarbone) and inserts at the mastoid process of the temporal bone and the occipital bone of the skull.
   • Primary functions: When one sternocleidomastoid muscle contracts, it rotates the head obliquely to the opposite side. When both muscles act together, they flex the neck forward and can assist in extending the head at the atlanto-occipital joint.

Usage Examples

• Noun:
  • A tight sternocleidomastoid muscle can cause neck pain and limited range of motion.
  • The physical therapist palpated the patient's sternocleidomastoid muscle to assess for tension.
  • The sternocleidomastoid muscle is clearly visible when a person turns their head to the side against resistance.

Advanced Usage

• Clinical significance: The sternocleidomastoid muscle is a key landmark in neck anatomy, dividing the neck into anterior and posterior triangles. It is often examined in cases of torticollis (wry neck), where spasm or shortening of the muscle causes the head to tilt.
• "To test the sternocleidomastoid": A common clinical instruction to assess the strength and function of cranial nerve XI (the accessory nerve), which innervates this muscle.
  • The neurologist asked the patient to turn her head against his hand to test the right sternocleidomastoid.

Variants and Related Words

• SCM: A common abbreviation used in medical and anatomical contexts.
  • The note indicated tenderness in the left SCM.
• Sternocleidomastoid (adjective): Pertaining to the muscle.
  • The surgeon identified the sternocleidomastoid region before making the incision.

Synonyms

• Sternomastoid muscle: An older, less precise term sometimes used interchangeably, though it omits the clavicular (cleido-) origin.
• Major muscle of the neck: A descriptive, non-specific synonym.

Related Phrases

• Sternocleidomastoid pain: Pain localized to this specific muscle.
  • His sternocleidomastoid pain was linked to poor posture at his desk.
• Sternocleidomastoid trigger point: A hyperirritable spot within the taut bands of the muscle that can refer pain to other areas, such as the head or face.

Noun

1. one of two thick muscles running from the sternum and clavicle to the mastoid and occipital bone; turns head obliquely to the opposite side; when acting together they flex the neck and extend the head