In 2010, the government approved Botox to treat chronic migraines, after some doctors noted that their patients reported having fewer headaches after receiving Botox injections to smooth out their wrinkles. But now a new review of the research suggests that Botox (onabotulinumtoxin A) actually has minimal headache benefit.
Dr. Jeffrey Jackson, professor of medicine at the Medical College of Wisconsin, reported on Tuesday in the Journal of the American Medical Association on a review of 31 trials investigating Botox’s effectiveness in reducing migraine and chronic tension headache symptoms. Studies comparing Botox to placebo showed a slight decrease in the number of migraine headaches per month among Botox users, but no difference between patients when it came to chronic tension headaches. In trials that compared Botox to other headache treatments, there was no statistically significant difference in the number of headaches patients reported each month.
“I was surprised that the [migraine] benefit was so minimal,” says Jackson. “I was also surprised that Botox doesn’t work to relieve tension headaches.”
Most chronic migraine sufferers who used Botox in the studies experienced just two to three fewer headaches each month on average, compared with those getting placebo injections.
For tension headaches, however, which the American Headache Society says is the most common type of headache, Botox doesn’t seem to be of much help at all. Botox is usually only prescribed for the 3% of adults whose tension headaches occur on 15 or more days a month, at which point they are considered to be chronic tension headaches. In most cases, stress, fatigue, hunger, overexertion or even poor posture can trigger headache onset. That’s why experts believed tension headaches could be particularly amenable to treatment with Botox, Jackson says: the theory was that the muscle-paralyzing drug would relax the contracting muscles that led to shear forces and strain in the skull, which could cause tension headache pain.
But according to his latest results, Jackson says the theory behind what causes tension headaches may need revising. “Botox’s lack of effect on tension headaches suggests that the old theory of muscles contracting is probably not true,” he says.
In fact, doctors don’t really know what processes in the brain are responsible for triggering either migraine or tension headaches; other theories suggest that the pain is caused by events within the brain. “Why in the world getting injections at different sites on the outside of the head should affect headaches that are supposedly driven by vascular phenomena and weird blood flow inside the brain itself — I don’t know,” he says. “We don’t understand [what is causing] either type of headache.”
So why is Botox approved to treat chronic migraines when it doesn’t seem to reduce episodes dramatically? In the studies that the Food and Drug Administration reviewed before approving the treatment — which were sponsored by Botox’s manufacturer, Allergan — the benefit was most pronounced, says Jackson. When he and his colleagues added in other studies that have been conducted since then, the effect waned. “I suspect that if the FDA knew the benefit was that small, they probably wouldn’t have approved the treatment for migraines,” he says.
Even so, he acknowledges that for migraine sufferers, having two to three fewer episodes a month is a welcome relief, so he recommends that anyone with frequent migraines try Botox injections; the shots are relatively safe, and if they can reduce any headache pain, then they might be worth a try. But people with chronic tension headaches or those who aren’t sacked by 15 or more episodes a month, probably aren’t going to benefit, he says.