Early efficacy and late gain in chronic and high-frequency episodic migraine with onabotulinumtoxinA.

OnabotulinumtoxinA efficacy is significant at 6 months in frequency and analgesic intake and remains stable during follow-up, whilst the intensity of pain decreases in a stepwise manner at each time point of the analysis. The improvement in CM and HFEM patients is proportional and significant after 1 year of treatment.