botox for chronic migraines
Botox (onabotulinum toxin A) was licensed specifically for the treatment of chronic migraine in July 2010 by the Medicines and Healthcare products Regulatory Agency (MHRA). Botox has not been shown to be effective for any other headache type (e.g. episodic migraine, tension-type headache, cluster headache) as yet. This fact sheet outlines the evidence for the use of botulinum toxin in headache.
What is botulinum toxin?
Botulism – paralysis of muscles caused by high doses of botulinum toxin – was first described in 1817. The responsible bacterium, Clostridium botulinum, was not isolated until 1895. Seven different subtypes of botulinum toxin (A-G) are known. A highly dilute preparation of botulinum toxin type A (botox) was introduced in clinical practice in the 1970s and 1980s to treat squint and blepharospasm. Since then it has found uses in other areas of medicine including dystonia (including writer’s cramp), post-stroke spasticity, and hyperhidrosis. Other botulinum toxin preparations are available, both of type A (Dysport and Xeomin) and type B (Neurobloc or Myobloc), but these have never been tested in headache disorders.
Botulinum toxin and headache
In the mid-1990s a number of people reported improvement in headaches in patients receiving botulinum toxin for other reasons. Well-conducted clinical trials of botulinum toxin in various types of headache followed, but the results were disappointing, with no difference over placebo being found in tension-type headache, episodic migraine, and undifferentiated chronic headache. Detailed analysis of the results suggested, however, that there might be a subgroup of patients with chronic migraine who could benefit, and further trials were undertaken.