Critical Care Registered Nurse (CCRN) Practice Exam

Which cranial nerve is tested by asking a patient to wrinkle their forehead and smile?

1. CN V

2. CN VII

3. CN IX

4. CN XI

The correct answer is: CN VII

The cranial nerve tested when asking a patient to wrinkle their forehead and smile is the facial nerve, known as cranial nerve VII. This nerve is responsible for the innervation of the muscles of facial expression. When a patient is asked to perform these actions, it assesses the functionality of this nerve, as any weakness or inability to perform these movements may indicate a dysfunction of the facial nerve. Cranial nerve V, the trigeminal nerve, primarily provides sensation to the face and motor functions for mastication, but it does not control the muscles of facial expression. Cranial nerve IX, the glossopharyngeal nerve, is involved in taste and the gag reflex, and does not play a role in facial movements. Cranial nerve XI, the accessory nerve, is responsible for motor functions to the sternocleidomastoid and trapezius muscles, which are not involved in facial expressions either. Therefore, the correct answer highlights the specific function of the facial nerve in controlling facial muscle actions.