Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology
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OnabotulinumtoxinA was approved for treatment of chronic migraine (CM) after publication of Phase 3 Research Evaluating Migraine Prophylaxis Therapy (PREEMPT) trials. However, the PREEMPT trials lasted only up to 1 year. The main aim of our retrospective study was to evaluate whether a prolonged treatment of onabotulinumtoxinA (18 months, six quarterly cycles) will sustain or further improve the efficacy results and the quality of life achieved at 6 and 12 months. ⋯ A positive modification in the consumption of analgesics over time was observed (p for trend <0.001). The mean acute drug latency strongly decreased over time. Our study confirmed that onabotulinumtoxinA is an effective treatment to reduce headache-related disability and improve patients' quality of life, highlighting that upon repeated administration, the therapy efficacy increases significantly and a progressive trend of "first-time response" is observed for the entire period under consideration.