episodic migraine definition
Chronic migraine is a distinct and relatively recently defined sub-type of Chronic Daily Headache. The International Headache Society defines chronic migraine as more than fifteen headache days per month over a three month period of which more than eight are migrainous, in the absence of medication over use. Episodic migraine is the other migraine sub-type, which is defined as less than 15 headache days per month.1.