| Botox & Migraine by Jack A. Klapper, MD, Denver, Colorado Like many other discoveries in medicine (such as penicillin), the use of Botox for the prevention of migraine came about accidentally. Plastic surgeons have been using Botox to treat wrinkles for a few years. Several patients who also happened to have migraines reported that their migraines improved following the injection of Botox into forehead and brow muscles. What is Botox? Botox (botulinum toxin) is a purified protein that belongs to a class of compounds known as neurotoxins. It was first approved by the FDA for the eye muscle disorders strabismus and belpharospasm in 1989 and has been used in other conditions where muscle hyperactivity is an underlying problem. The mechanism of action of Botox has been thought to be weakening or paralysis (depending on dose) of muscles by preventing the release of acetycholine, a signal that the nerves need to cause muscle contraction. This is the same substance which is produced in spoiled food and causes the illness known as botulism. However, in medical use, the Botox is injected directly into the muscles involved rather than absorbed into the bloodstream, and the doses used are much less than those which cause botulism. Why does it work? Based on the mechanism of action of Botox, it is unlikely that anyone would have thought to try it for migraines. Its success in treating some patients has caused problems for those who would attempt to explain why it would work in migraine. One possibility is that muscle tension may act as a trigger for migraine in the same way that light and odors do. By reducing muscle tension, Botox would be eliminating an irritant to the nervous system, which would then reduce the chances of a migraine developing. More recently, studies have shown that Botox may affect other nerve cell signallng systems that have to do with the perception of pain. In an animal model of pain, injection of Botox under the skin resulted in decreased response to painful stimuli. Traditionally, scientists have thought that the pain of migraine was due to swelling and inflammation of blood vessels, but perhaps muscle tension is more of a factor than previously appreciated. The evidence. To prove a medication's effectiveness, physicians and scientists generally look to carefully designed comparison studies (called double-blind placebo-controlled trials) in which neither the patients nor the researchers know who is getting the experimental treatment versus an inactive placebo treatment. There have been several open-label (not blinded or placebo-controlled) studies showing that Botox was successful in preventing migraines. To date, there has been only one placebo-controlled, double-blind study, which showed a modest effect at a total of 25 units, but not at 75 units. One would have anticipated that the 75 unit dose should have been more effective. This initial study may have been less than optimal for several reasons. The injection sites were based on plastic surgery considerations (wrinkle areas) rather than typical locations of migraine pain. Many migraine patients have neck pain or pain in areas other than the forehead or brow, and these areas were not injected in the study. In addition, the doses used may have been too small to effect a change. Several headache specialists who are using larger doses and injecting neck and temple muscles have had better results. Subsequent studies are planned to correct these possible deficiencies. In muscle tension headache, studies have shown better results. The duration of action of Botox in migraine prevention varies from about 10 to 13 weeks. Like other migraine preventives, the onset of effect may take a few weeks. Ideally, the treatment should not be administrated more frequently than every 3 months. Safety. Because Botox is a neurotoxin, there are concerns about its safety. However, it has had a remarkable good record since its introduction in 1989. Because it is injected into muscle and not absorbed into the system, side effects that occur frequently with other migraine preventives, such as drowsiness, dizziness, weight gain, and mental changes, are not seen with Botox. Some mild pain at the injection site for a day or two is about the only side effect our patients notice. Drooping of the eyelid is a common side effect but can usually be avoided by proper injection technique, and when it occurs, lasts only a few days. Who should try Botox? Currently, Botox is not approved by the FDA for headache treatment. The decision to use Botox should be based on a discussion with your physician. Failure to respond to standard migraine preventives or side effects from them should be an important consideration. Since the effect of Botox lasts about 3 months, one can weigh the costs of the injections versus the amount that would be spent on headache treatment during that time. |
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