This study is testing if Dysport® is safe and effective in stopping chronic migraines. A migraine is a severe headache that often throbs 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 of those being migraines. Dysport®, a medicine made from Botulinum toxin type A (BoNT-A), works by stopping chemicals that cause pain in the brain.

The study has three parts. First, there's a screening period lasting 6 to 12 weeks with 1 visit. Then, the first treatment phase lasts 24 weeks, with injections given on Day 1 and Week 12, requiring 4 in-person and 4 online visits. The second treatment phase is also 24 weeks with 3 in-person and 4 online visits, where all participants receive Dysport®.

• The study lasts up to 60 weeks (about 14 months).
• Participants must keep an e-diary and answer questionnaires.
• There will be physical exams, blood, and urine tests.