Clinical Uses of Botulinum Toxins: Botulinum toxin type A for the prophylactic treatment of primary headache disorders

Introduction Migraine is a chronic neurovascular disorder that afflicts 8–15 per cent of the world's population and is the most common primary headache disorder in clinical practice. In the United States there are an estimated 28 million migraine sufferers, with women being affected three times as often as men. It is characterized by severe headaches and is often associated with nausea, vomiting, heightened sensitivity to sound and light, and focal (paresthesias, visual scintillations) and global (impaired concentration) neurological dysfunction. Migraine is considered to be one of the top 20 causes of disability due to chronic diseases, and severe migraine has been judged by the World Health Organization to be as disabling as quadriplegia, psychosis, and dementia. Most sufferers are in their most socially active and productive years (25–55). Not only is migraine painful and disabling for the sufferer, but it exerts a significant economic burden on society. It causes 112 million bedridden days each year and costs $14 billion in reduced productivity and missed workdays. The economic burden of migraine is comparable with that of diabetes and higher than that of asthma. Even among migraineurs who consult a physician, many are not satisfied with their therapy and report that prescribed medications are not always optimal. Triptan medications, the most effective acute therapy for migraine attacks, are only effective in improving the pain and associated migraine symptoms, such as photophobia and nausea, in up to two thirds of patients.