Trigeminal Nerve | Cranial Nerve VII / CN VII Assessment

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Facial Nerve | Cranial Nerve VII / CN VII Assessment

The facial nerve (CN VII), as the name suggests, provides innervation to the muscles necessary for facial expressions except those involved in eyelid elevation, which is achieved by the oculomotor nerve. While it’s primarily a motor nerve, it does have a sensory division sometimes referred to as the “nervus intermedius” to the anterior two-thirds of the tongue as well as a reflex function involving the corneal reflex and glabellar reflex. It may be affected by, for example, cerebral infarct or conditions such as Parkinson’s Disease and results in facial palsy.

Motor Assessment

Start by examining the patient’s face. Facial palsy may already be apparent by the presence of asymmetries such as flattening of the nasolabial groove. Facial nerve palsy can show as an upper or lower motor neuron lesion. In upper motor neuron lesions, the muscles of the forehead are spared. So ask the patient to look up and raise the eyebrows and observe for even wrinkling of the forehead. Ask the patient to close the eyes tightly while you try to force them open.

Muscles in the lower half of the face can be tested by asking the patient to show their teeth, smile, or puff out the cheeks while you palpate them for even tone.

The lower motor neuron lesion pattern of facial palsy will show paresis/paralysis of all ipsilateral facial muscles including the forehead.

Reflex Assessment

We have covered the corneal reflex in our post on the oculomotor nerve. For the glabellar reflex, the patient is asked to keep the eyes wide open while you apply a series of taps on their forehead with your finger. A normal response would be no blinking. An abnormal response is repeated blinking upon tapping of the forehead.

At last, examine for an exaggerated jaw reflex. Place one index finger on the chin and tap it with your reflex hammer. Normally you would observe slight closure or no reflex at all.