Onabotulinum toxin A for treatment of chronic migraine with medication overuse.

Chronic migraine is a common and debilitating headache syndrome. Botulinum neurotoxin (BoNT), a potent toxin produced by the anaerobic bacterium Clostridium botulinum, used largely for treatment of disorders associated with increased muscle tone and hyperidrosis, has been recently used for patients suffering from chronic migraine. In this study, two groups of patients were treated with different dosages of BoNT A to verify the efficacy for chronic migraine. The results confirmed the efficacy of BoNT A when used at the dosage of 150 U. In the second group of patients treated with 100 U, results were not significant. Although these results are preliminary, they led to intense efforts to evaluate the analgesic properties of BoNT A and to assess their clinical applicability.