A 42-year-old woman presents with weakness and drooping on the right side of her face. Her husband noticed the sudden changes in her facial features last night. She has difficulty closing her right eye but can do so with effort. She has had a headache off and on for a week that resolves with acetaminophen. She believes the headaches are a result of having the flu a week ago and is not experiencing any other symptoms. Her vital signs are within the normal range. Which of the following is the best test for determining the cause of her facial symptoms? Ask the patient to raise both eyebrows Computed tomography scan of the head Nasopharyngeal swab for influenza testing Nerve conduction study