Chronic migraine

The classification of the International Headache Society (IHS) generally differentiates episodic from chronic headache. Chronic migraine is defined as headache on 15 and more days a month over more than 3 months and headache on 8 days or more fulfils the criteria for migraine or were triptan/ergot-responsive when thought to be migrainous in early stages of the attack. The prevalence of chronic migraine is estimated at 2-4 %. The quality of life is highly compromised in this condition and comorbidities are much more frequent compared to episodic migraine. Data from prospective randomized studies are scarce as most patients with chronic migraine were excluded from previous trials and only few studies were conducted for this condition. The efficacy for prophylactic treatment compared with placebo is proven for topiramate and onabotulinum toxin A.