Muscle
Sternocleidomastoid
Key neck landmark
High-yield
CN XI (spinal accessory). Contralateral rotation + ipsilateral tilt; bilaterally flexes the neck. Landmark for the neck triangles.
Overview
A strap muscle dividing the neck into anterior and posterior triangles that flexes the neck and rotates the head to the opposite side.
Reference facts
- Origin
- Sternal head: manubrium. Clavicular head: medial third of the clavicle
- Insertion
- Mastoid process and lateral superior nuchal line
- Action
- Tilts the head to the same side and rotates the face to the opposite side; bilaterally flexes the neck
- Innervation
- Spinal accessory nerve (CN XI); proprioception C2, C3
- Blood supply
- Occipital and superior thyroid arteries
Clinical correlation
Congenital torticollis involves a fibrosed sternocleidomastoid.
Frequently asked questions
What does the sternocleidomastoid do?
The sternocleidomastoid tilts the head to the same side and rotates the face to the opposite side; bilaterally flexes the neck.
What nerve innervates the sternocleidomastoid?
The sternocleidomastoid is innervated by the spinal accessory nerve (CN XI); proprioception C2, C3.
Where does the sternocleidomastoid attach?
Origin: Sternal head: manubrium. Clavicular head: medial third of the clavicle. Insertion: Mastoid process and lateral superior nuchal line.
What is the blood supply of the sternocleidomastoid?
The sternocleidomastoid is supplied by the occipital and superior thyroid arteries.