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.