Botulinum toxin for the treatment of headache: a promising path on a "dead end road"?

Available preventive treatments for primary headaches such as migraines and tension-type headaches have limited efficacy and often disabling side effects (Schoenen 2004, Schoenen 2000). There is thus room for new more effective and better tolerated therapeutic approaches as long as they can be proven superior to placebo. Based on pilot studies and open trials, botulinum toxin (BT) appeared in the headache armamentarium more than a decade ago and it remains widely used in North America since. The initial enthusiasm for BT was not confirmed by subsequent randomized controlled trials reviewed in this article, neither in tension-type headache, nor in episodic migraine and hence BT was considered a "dead end road" by certain headache experts. A promising "path" for BT may, however, exist. In two recent trials (PREEMPT 1 and 2), OnabotulinumtoxinA (Botox) was found effective in chronic migraine. The therapeutic gain over placebo is modest (+/- 11%), but chronic migraine is most disabling, often drug resistant and a serious public health problem, as it affects 1-2% of people in the general population. Because the PREEMPT trials leave unsolved a number of clinically relevant questions, OnabotulinumtoxinA cannot become yet the pre-emptor of CM treatment. Although the path is promising, it seems wise, at this stage, to restrict its use to specialized headache centres where BT can be included in a multidisciplinary approach for chronic headache patients.