A 47-year-old woman is complaining of paroxysmal headaches that have been occurring for the past 5 years. The pain is unilateral, intense, and localized in the frontal area. It is accompanied by nausea and abdominal discomfort and begins suddenly. The headaches are preceded by blurred vision. The woman has a history of hypertension episodes, but currently takes no medicines. Between the headaches, her condition is satisfactory. She is overeating (body mass index is 29), her blood pressure is 170/95 mm Hg. Her neurological status is normal. Make the right diagnosis: