An 18-year-old woman comes to the clinic due to persistent headaches, which have occurred daily for 3 months. The headaches are holocranial, pulsating, and especially bothersome at night Ibuprofen has not helped the pain. The patient has double vision when looking sideways and blurry vision in both eyes. She has no history of head trauma prior to the onset of symptoms and no fever, vomiting, photophobia, or weakness. The patient has no chronic medical conditions and does not use tobacco, alcohol, or illicit drugs. Her mother and sister have migraine headaches. Temperature is 37 C (98.6 F), blood pressure is 130/85 mm Hg, and pulse is 90/min. BMI is 34 kg/m2. Physical examination shows no nuchal rigidity or sinus tenderness. Eye examination reveals optic disc edema and left lateral rectus palsy. CT scan of the head without contrast is normal. Which of the following is the best next step in management of this patient? A. CT angiogram of the head B. CT scan of the paranasal sinuses C. Erythrocyte sedimentation rate D. Lumbar puncture with opening pressure E. Sumatriptan abortive therapy