Overview of the international classification of headache disorders (ICHD III)

Abstract

In order to effectively study and manage headache disorders, diagnosis is essential. In both research and clinical areas, separating secondary causes from primary headache disorders is a crucial first step, followed by further specificity within these broader categories. Historical approaches to classifying headache disorders culminated in the International Classification of Headache Disorders (ICHD), published in 1988. This was revised as the International Classification of Headache Disorders, (ICHD II) in 2004. The International Headache Society's Subcommittee on Classification began work on the 3rd edition in 2010. ICHD-3 was published as the first issue of Cephalalgia in 2018, followed the publication of ICHD-3 beta version in 2013. The idea behind the beta version was to promote more field testing before presentation of the final ICHD-3. There have been excellent field-testing studies published, in migraine with aura, cluster headache, idiopathic intracranial hypertension and trigeminal neuralgia among others. Consequently, these symptoms are included only in the Appendix of ICHD-3, where they invite further study. These are examples of the evidence-based process of disease classification that now underpins all future changes to the ICHD. The diagnostic criteria for more than 200 causes of headaches are based upon evidence when available, of a number of primary and secondary headache disorders. This presentation will attempt to provide an overview of the rationale behind the ICHD, a guide to its use, and a summary of important diagnostic features of the primary and secondary headaches, particularly where these have changed significantly in the ICHD III from ICHD II.