Treatment of chronic migraine.

Chronic migraine is defined in different ways. The most commonly used definition is headache on more than 15 days per month in patients with migraine. Chronic migraine is difficult to treat and requires a multidisciplinary approach. Only two pharmacological treatments have been shown to be effective in placebo-controlled randomized trials: topiramate and local injection of botulinum toxin. Both therapies are effective in patients with chronic migraine with and without medication overuse. Many other substances have been investigated in chronic daily headache. All trials were underpowered and, therefore, recommendations concerning possible efficacy are not possible.