Face and neck muscles let us show emotion, chew, swallow and hold up and turn the head. Each group has its own cranial nerve, so testing the muscles checks those nerves.
Facial expression
Thin muscles under the skin, such as the frontalis, orbicularis oculi, orbicularis oris and buccinator, move the face. All are supplied by the facial nerve (cranial nerve VII).
Chewing
The masseter, temporalis and pterygoid muscles move the jaw. They are supplied by the trigeminal nerve (cranial nerve V).
Neck
The sternocleidomastoid turns the head to the opposite side and the trapezius shrugs the shoulder. Both are supplied by the accessory nerve (cranial nerve XI).
Forehead sparing
The upper face gets signals from both sides of the brain, the lower face mainly from the opposite side. A stroke usually spares the forehead, while a facial nerve palsy such as Bell palsy weakens the whole side.
| Muscle group | Nerve | Quick test |
|---|---|---|
| Facial expression | Facial (VII) | Raise eyebrows, squeeze eyes shut, smile |
| Chewing | Trigeminal (V) | Clench teeth, feel the masseter |
| Sternocleidomastoid and trapezius | Accessory (XI) | Turn head and shrug against resistance |
At the bedside
Testing these muscles is part of the cranial nerve exam. A drooping lower face with a normal forehead raises concern for stroke and needs urgent action.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).