Investigating prophylactic botulinum toxin type A for chronic headache disorders.

There is an increasing number of studies on botulinum toxin A in the treatment of idiopathic and symptomatic headache; however, many studies can hardly be compared with each other because of different end points and different trial designs. For the prophylactic treatment of tension-type headache, migraine and cervicogenic headache, no sufficient positive evidence for a successful treatment can be obtained from the randomised, double-blind and placebo-controlled trials performed so far. For the treatment of chronic daily headache (including medication-overuse headache), there is inconsistent positive evidence for subgroups (e.g., patients without other prophylactic treatment). This means that most of the double-blind and placebo-controlled studies do not confirm the assumption that botulinum toxin A is efficacious in the treatment of idiopathic headache disorders; however, it is possible that some subgroups of patients with chronic migraine benefit from a long-term treatment for > or = 6 months.