Classification of primary headaches.

Given the range of disorders that produce headache, a systematic approach to classification and diagnosis is an essential prelude to clinical management. For the last 15 years, the diagnostic criteria of the International Headache Society (IHS) have been the accepted standard. The second edition of The International Classification of Headache Disorders (January 2004) reflects our improved understanding of some disorders and the identification of new disorders. Neurologists who treat headache should become familiar with the revised criteria. Like its predecessor, the second edition of the IHS classification separates headache into primary and secondary disorders. The four categories of primary headaches include migraine, tension-type headache, cluster headache and other trigeminal autonomic cephalalgias, and other primary headaches. There are eight categories of secondary headache. Important changes in the second edition include a restructuring of these criteria for migraine, a new subclassification of tension-type headache, introduction of the concept of trigeminal autonomic cephalalgias, and addition of previously unclassified primary headaches. Several disorders were eliminated or reclassified. In this article, the authors present an overview of the revised IHS classification, highlighting the primary headache disorders and their diagnostic criteria. They conclude by presenting an approach to headache diagnosis based upon these criteria.