Chronic Migraine is a distinct and severe neurological disorder characterized by patients who have a history of migraine. Health Canada approved Botox (r) as prophylactic treatment for chronic migraine headaches. Health Canada's approval of BOTOX® is based on data collected in Allergan's PREEMPT (Phase III Research Evaluating Migraine Prophylaxis Therapy) program, which was designed to evaluate the safety and efficacy of BOTOX® as a preventive treatment of headaches in adults with Chronic Migraine. Treatments are usually done every 3 months.