Spinal Accessory Nerve (CN 11): Neck Strength (Trapezius & Sternocleidomastoid)
Sternocleidomastoid and Trapezius Muscles at Rest
- To assess the function of cranial nerve 11, assess the patient’s sternocleidomastoid and trapezius muscles. First inspect and palpate these muscles’ size and symmetry at rest. Bilateral sternocleidomastoid weakness will cause weakness of neck anteroflexion and may manifest with the patient holding the neck in extension at rest. Trapezius muscle weakness may manifest with drooping of the patient’s shoulder or flattening of the patient’s trapezius ridge.
Sternocleidomastoid and Trapezius Muscles in Action
- 1. Sternocleidomastoid. In this example, we will indicate how to evaluate the right sternocleidomastoid (the opposite method is used for the left).
A. Lateral rotation of the head.
i. The patient should turn his/her head to the left.
ii. Palpate the patient’s right sternocleidomastoid to feel its activation.
iii. Place one hand on the patient’s left cheek and the other hand on the patient’s right shoulder.
iv. Ask the patient to sustain the left head turn while you attempt to push the patient’s head back towards center.
B. Vertical rotation of the head.
i. Place one hand on the patient’s forehead and the other on the patient’s C7 vertebrae.
ii. Ask the patient to hold his/her head still while you press on the patient’s head (push backward) and brace the patient’s neck by pressing on the patient’s C7 vertebrae.
2. Trapezius.
A. Shoulder raise.
i. Ask the patient to raise his/her shoulders by telling him/her to “use your shoulders to try to touch your ears”.
ii. Place your hands on the patient’s shoulders and press down.
iii. This is repeated from both the front and back. Observe for scapular winging.
