Duration of migraine is a predictor for response to botulinum toxin type A

Objective. - To identify the clinical characteristics and/or injection parameters that predict a favorable response to botulinum toxin type A in patients with episodic and chronic migraine. Background. - There is emerging scientific and clinical evidence to support the utility of botulinum toxin type A (BoNT-A) in the prophylaxis of episodic and chronic migraine headache. However, the patient characteristics and injection strategies that predict a favorable treatment response are unknown. Methods. - We conducted a prospective, open-label study on 74 patients from our clinic receiving BoNT-A for episodic or chronic migraine. For all patients, migraine-related disability (Migraine Disability Assesment [MIDAS]), headache frequency, and average headache intensity were obtained at baseline and at 3 months post-BoNT-A. Information regarding demographic characteristics and injection parameters was also collected. Results. - Sixty-one patients met the study criteria and were available for 3-month follow-up. At the 3-month follow-up visit, the mean MIDAS scores of the 61 qualified study patients had decreased from 102 at baseline to 49 (52% decrease, P < .001). The mean number of headache days was reduced from 60 to 39 (P < .001), and the mean headache intensity decreased from 7.6 at baseline to 5.9 (P < .001). Frequency of migraine attacks, presence of analgesic overuse, total BoNT-A dose, and presence of underlying muscle tenderness were not predictive of treatment response. Age and duration of migraine were the only clinical factors significantly predictive of treatment response. Age likely was a predictor only as a consequence of duration of illness as subjects with migraine duration greater than 30 years were significantly less likely to respond to treatment with BoNT-A. Conclusion. - BoNT-A may be effective in decreasing headache frequency, headache intensity, and headache-related disability in episodic and chronic migraine patients. Duration of illness emerged as a predictor of treatment response. Randomized controlled studies should evaluate headache-related disability as a primary endpoint in patients with episodic and chronic headache.