Factors associated with favorable outcome in botulinum toxin A treatment for chronic migraine: A clinic-based prospective study.

[BACKGROUND] Botulinum toxin A (BTA) responders have elevated levels of calcitonin gene-related and vasoactive intestinal peptides, which are potent vasodilators. We aimed to investigate neurovascular features as a predictor of BTA treatment response in patients with chronic migraine.

[METHODS] We prospectively recruited South Korean patients who were diagnosed with chronic migraine and underwent BTA injection at a university hospital from December 2013 to January 2015. Interictal transcranial Doppler (TCD) test was performed before BTA treatment when patients did not experience moderate-to-severe headache attacks. Botulinum toxin A was injected per the Phase III REsearch Evaluating Migraine Prophylaxis Therapy (PREEMPT) protocol. Treatment response was determined after 4-6 weeks of follow-up. Pretreatment clinical and neurosonologic features of responders and non-responders were analyzed.

[RESULTS] Of the 83 enrolled patients, 70 who completed initial and follow-up evaluations were included for this study. Forty-two (60.0%) patients were classified as responders. 50% responders were 31 (44.2%). Longer disease duration was associated with poor treatment outcome (p=0.019). The ratio of the mean velocity of middle cerebral artery to that of ipsilateral internal carotid artery (MCA/ICA index) was significantly higher in responders than non-responders (p=0.027) and remained significant after controlling for covariates (p=0.025).

[CONCLUSIONS] Shorter disease duration and higher pretreatment MCA/ICA index on TCD are associated with good early outcomes of BTA treatment.