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Botulinum Toxin Injections for Headache
Case History Submitted by: Randolph W. Evans, M.D.
Expert Opinion by: Andrew Blumenfeld, M.D.
Posted October 2003

Botulinum toxin injections for migraine? It seemed crazy to many when first suggested by otolaryngologist William Binder. In 1992, he noted that migraineurs who received injections for wrinkles reported an improvement in their headaches, and additional evidence for efficacy has accumulated since. Serendipity strikes again!

In patients who have migraine with aura, botulinum toxin type A therapy frequently produces improvement in head pain, but the aura remains unchanged. This may be related to the mechanism of action of botulinum toxin type A in migraine, wherein the drug is hypothesized to affect the trigeminal nerve predominantly. Triptan responsiveness often improves following botulinum toxin type A treatment, but patients with allodynia will continue to have a poor response to triptans. It would be interesting to study the effects of botulinum toxin type A on allodynia in patients with migraine.

Although patients improve after one treatment, repeated treatments produce even greater clinical efficacy, particularly with respect to changes in Migraine Disability Assessment (MIDAS) scores. Three treatments of botulinum toxin type A over a 9-month period should be considered adequate to determine whether the patient will or will not be a responder to botulinum toxin therapy. To insure appropriate expectations, patients should be advised about the progressive efficacy of repeated treatments. Each successive treatment may involve higher doses and varied combinations of fixed-site and follow-the-pain approaches.

Botulinum toxin type A therapy may be effective in the management of chronic daily headache. The technique of injection involves a fixed-site approach for migrainous headaches, as for the first case, with the addition of a follow-the-pain approach for headaches with tension-type features. Follow-the-pain injection sites include the frontalis, temporalis, occipitalis, trapezius, splenius capitus, suboccipital, and cervical paraspinal muscles. Injection sites are identified by history ("Where does it hurt when you have a headache? " and "Show me with your hands where the pain is."), and by examination of the cervical-shoulder girdle and temporomandibular musculature. The doses injected in the cervical-shoulder girdle muscles are kept low, so as to prevent any possible weakness.

For all types of headache, the dose of botulinum toxin type A is in the range of 50 to 100 units. The technique of delivering small doses at multiple sites reduces the occurrence of side effects and controls head pain effectively. To achieve this, a dilution of 4 mL of normal saline to 100 units of botulinum toxin type A is used. The dose at each site is 2.5 (0.1cc) to 5 units (0.2 cc). The injections are administered intramuscularly to limit discomfort and side effects imported by soft tissue diffusion. Intradermal injections may produce a similar clinical improvement but tend to be more uncomfortable. Owing to the potential risk of antibody development, botulinum toxin type A treatments should not be repeated more frequently than every 3 months.