Onabotulinum toxin A (BT-A) is now one of the authorized prophylaxis treatments for chronic migraine (CM) thanks to previous clinical trials, which usually required a pharmacologic washout as a precondition for demonstrating its efficacy. Aim of our study was to assess the efficacy in daily clinical practice of BT-A injections in refractory CM patients, regardless of medication overuse without any standardized withdrawal protocol and without stopping the ongoing prophylaxis treatment as well. We treated 44 refractory CM patients (37 females and 7 males) trimonthly without any modification in symptomatic, or prophylactic drug therapy. Main efficacy variables included number of headache, or migraine days and episodes, total cumulative headache hours, MIDAS and HIT-6 scores; all items were assessed at baseline and at the 12-, 24-, and 36-week follow-up. All variables showed a statistically significant improvement at week 36. In general, more than 50 % of patients had a good clinical outcome (including all improved patients, either partial or full responder) and that the percentage of drug abuser patients significantly decreased from 75 to 50 %, thanks to a spontaneous reduction of the symptomatic drug intake. Adverse events were uncommon and did not require treatment discontinuation. Onabotulinum toxin A treatment in refractory CM patients with unsatisfactory prophylactic drug treatments and pharmacological abuse is effective in improving clinical outcome and quality of life. This result may be achieved through a flexible pharmacologic approach tailored to each patient's needs; moreover, the patient himself can be often expected to reduce drug consumption spontaneously.
Keywords: BT-A; Chronic migraine; Medical overuse; Onabotulinum toxin; Refractory chronic migraine.