Abstract

Chronic daily headache(CDH) refers to a category of headache disorders that are characterized by headaches occurring on more than 15 days per months. This category subdivided into primary and secondary CDH disorders. Common primary CDH disorders included transformed migraine, chronic migraine, new daily persistent headache, medication overuse headache and hemicrania continua. According to ICHD-II criteria, most CDH has more than one diagnosis. Chronic migraine in ICHD-II is restrictive and only small portion of CDH patients were diagnosed as chronic migraine. Silberstein and Lipton proposed transformed migraine for frequent association of migraine and migrainous features in CDH. In 2005, revised diagnostic criteria for broader concept of chronic migraine was ented in appendix of ICHD-II. According to new criteria, more than 80% of CDH patients were classified as having chronic migraine.