A hospitalized patient with a history of cluster headache awakens during the night with a severe stabbing headache. Which action should the nurse take first?

A: "Observing for facial symmetry." Facial symmetry evaluates cranial nerve VII (facial nerve), which is responsible for controlling the muscles of facial expression. While facial symmetry is an important aspect of a neurological examination, it does not relate to cranial nerve III, which has different functions.
B: "Eliciting the gag reflex." The gag reflex tests cranial nerves IX (glossopharyngeal) and X (vagus). The gag reflex is essential for assessing the integrity of these nerves, which play a role in swallowing and the gag response, but it is not relevant to cranial nerve III.
C: "Testing visual acuity." Visual acuity primarily assesses cranial nerve II (optic nerve), which is responsible for vision. While checking visual acuity is crucial for a comprehensive neurological examination, it does not evaluate cranial nerve III, which has functions related to eye movement and pupil response.
D: "Checking the pupillary response to light." Pupillary response directly assesses cranial nerve III (oculomotor nerve), which controls the muscles that constrict the pupils and move the eyes. Evaluating the pupillary response to light involves shining a light into each eye and observing the constriction of the pupil. A normal response indicates that the oculomotor nerve is functioning properly, while an abnormal response may suggest potential neurological issues, such as increased intracranial pressure or damage to the nerve itself. This assessment is vital for understanding the client's neurological status.

A. Whisper in one of the client's ears while occluding the other. This test assesses cranial nerve VIII (vestibulocochlear nerve), which is responsible for hearing and balance. It does not evaluate cranial nerve XI (spinal accessory nerve).
B. Observe for the ability of the client to turn their head side to side. Cranial nerve XI (spinal accessory nerve) controls the sternocleidomastoid and trapezius muscles, which are responsible for head turning and shoulder shrugging. The nurse should ask the client to turn their head against resistance and shrug their shoulders while applying gentle pressure, assessing the strength and function of this nerve.
C. Have the client identify specific smells. Identifying specific smells such as coffee and lemon tests cranial nerve I (olfactory nerve), which is responsible for the sense of smell. Cranial nerve XI does not influence olfaction.
D. Check the client's visual acuity using a Snellen chart. The Snellen chart is used to assess cranial nerve II (optic nerve), which is responsible for vision. Cranial nerve XI does not play a role in vision or visual acuity.