Chronic Migraine - Evolution of the Concept and Clinical Implications.

OBJECTIVE: The current definition of chronic migraine is relatively new. This definition has been field tested multiple times and has gone through multiple revisions. The evolution of the concept of migraine and its transformation to involve the category of chronic migraine is outlined.

DISCUSSION: Chronic migraine as a disease was initially recognized in patients seen in headache clinics with a large burden of disability from frequent headaches and a history of prior migraines. Over time, this observation was operationalized into multiple diagnostic criteria with requirements for frequent headache days, typically 15 or more, and additionally a certain predisposition to migraine phenotype whether counted in number of headaches with migrainous features or a transformation from migraine in certain diagnostic criteria. In addition, the observation of medication overuse in this population raises a valid question - whether this is a factor for chronification versus a separate secondary headache etiology.

CONCLUSION: Chronic migraine is a relatively newly recognized disease. We have an increasing number of medications studied specifically in chronic migraines, and these are briefly introduced. Additionally, there are guidelines to help design trials in chronic migraine. A valid future research question is to further study the efficacy of the medications studied in an undifferentiated migraine population, as there is economic pressure to use these medications as first line.