Chronic migraine can be diagnosed using criteria of the International Headache Society (IHS).
Patient selection: headache
Features of chronic migraine:
(1) history of migraine headaches
(2) average migraine frequency >= 15 days per month for >= 3 months
(3) all of the following:
(3a) attacks meet criteria for migraine without aura
(3b) no use of symptomatic drugs
(3c) not attributable to another disorder
