This study aims to see if Dysport®, a medicine made from Botulinum toxin type A, is safe and works well in preventing chronic migraines. A migraine is a headache with a pounding pain, usually on one side of the head, and can make you feel sick and sensitive to light and sound. Chronic migraine means having headaches for at least 15 days a month, with at least 8 being migraine days. Dysport® helps by stopping chemicals in the brain that cause pain. The study has three parts: a screening period (6-12 weeks) to see if you can join, and two treatment phases (each 24 weeks long) with injections. You'll have visits to the clinic and online, plus keep a diary and answer questions. The study lasts about 14 months.

• Participants must be 18 or older and have had chronic migraines for over a year.
• You'll have clinic visits and remote check-ins; receive injections at specific intervals.
• Participants can continue some other medications but need to record them.