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Recurrent vascular headaches not preceded or accompanied by an aura. In general, episodes have the following characteristics: duration of 4-72 hours, moderate to severe intensity, throbbing quality, unilateral cranial distribution, and aggravation by physical activity. Nausea, emesis, photophobia, or phonophobia accompanies the pain. (From Headache Classification Committee of the International Headache Society. Classification and diagnostic criteria for headache disorders, cranial neuralgias and facial pain. Cephalalgia 1988;8:Suppl 7:1-96)