Anecdotal reports from patients receiving Botulinum Toxin Type A (Botox®) for the treatment of wrinkles suggested that this treatment may prove useful as a migraine preventive. A retrospective patient chart review associated migraine relief with certain Botulinum Toxin Type A injection sites. In addition, this retrospective analysis of 96 patients showed 51 percent of patients had complete relief of headache for an average of 3.6 months after injection, and 78 percent had at least a 28 percent decrease in headache frequency. Such findings sparked the initiation of further studies described below.

Two double-blind, placebo-controlled trials evaluated the efficacy of Botulinum Toxin Type A in migraine patients. At baseline, patients had two to eight migraines per month in Study 1 and four to eight in Study 2. Patients were excluded if they had more than 15 headache days each month. Following a one-month observation period, researchers treated the patients with nine injections in frontalis/glabellar muscles and two in temporalis muscles.

In Study 1, 25 unit doses of Botulinum Toxin Type A proved significantly more effective than placebo at two and three months after injection. In addition, 25 units of botox led to a significant decrease in acute medication use compared to placebo, whereas no such finding was observed at any dose in the placebo-treated group. (A higher dose of 75 units in study 1 was not more effective than placebo.) In Study 2, there was no significant difference between patients receiving Botulinum Toxin Type A doses of 7.5, 25, and 50 units and placebo-treated patients. The most significant side effects included ptosis, injection site weakness, and skin tightness. Overall, treatment was safe and well tolerated.

In addition to the double-blind, placebo-controlled data presented, researchers presented a retrospective study of 38 patients, each with an average of six International Headache Society-defined migraines per month. Physicians selected Botulinum Toxin Type A injection sites and doses. Depending upon pain distribution, trigger points, and frown lines, physicians injected patients in ten to 25 sites. Additional sites sometimes injected in this study, but not in the placebo controlled trials, included splenius capilis paraspinal cervical muscles and the trapezius muscle. Doses varied from 20-100 units. Doctors observed a 50 percent reduction in frequency or severity of migraine in 71 percent of treated patients. Only two adverse effects from Botulinum Toxin Type A were reported-one patient developed nausea, and one developed a headache.

In summary, the verdict on Botulinum Toxin Type A for the treatment of migraine is not yet in. There are several promising studies, but results of double-blind placebo-controlled trials are mixed. More studies, including double-blind studies that allow physicians to select sites specific to each patient, need to be performed. Until these studies are done, Botulinum Toxin Type A will probably be reserved for unusual circumstances and refractory cases.