Classification of Headache

Abstract

In order to effectively study and manage headache disorders, diagnosis is crucial. For most patients with headache, an important first step clinically is to rule out curable causes, including those due to vascular, infectious, neoplastic, and other processes. A classification schema for these many causes of headache is an important tool for making a correct diagnosis. Once secondary headache causes are ruled out, it is crucial to determine which primary headache disorder is present. But the problem clinicians encounter here is that primary headaches do not have laboratory markers, so diagnosis is phenomenological. Hence, classification of these headaches is imperative as well. Historical approaches to classifying primary and secondary headache disorders culminated in the International Classification of Headache Disorders (ICHD) completed and published in 1988. This was revised as the International Classification of Headache Disorders, 2nd edition (ICHD II) in 2004. Currently, the International Headache Society is engaged on a third edition which is projected to be completed in 2013. These classification systems are based on evidence when available, and, fortunately, research in the field of headache medicine has produced useful data applicable to classification of a number of primary and secondary headache disorders. This chapter provides a practical overview of the rationale behind the ICHD and diagnostic features of the primary and secondary headaches.