OnabotulinumtoxinA for the treatment of chronic migraine.

Chronic migraine is a common primary headache disorder that actively afflicts as many as 1 in 50 individuals and accounts for a disproportionate share of the financial cost, pain, and emotional suffering produced by migraine generally. “Chronic migraine” implies that one has an established history of migraine, has been experiencing headaches on at least 15 days of each month for at least 3 consecutive months, and the majority of those headaches each month either have had features characteristic of migraine or have been responsive to drugs which are relatively specific for migraine (examples: sumatriptan, rizatriptan, dihydroergotamine).