The International Classification of Headache Disorders: History and future perspectives.

PURPOSE:The International Classification of Headache Disorders (ICHD) is universally accepted and forms the basis of headache management and clinical, experimental and pharmacological headache research. The present review summarizes the history of the three different editions of the classification, concentrating on aspects of general interest that are still valid today. METHODS:The article is based on the memory of the chairperson of three editions of the International Classification and on his notes in the work copies and published scientific classification studies. RESULTS:Many of the crucial issues in headache classification are discussed in the review of the different editions. Some have been resolved and some remain unresolved. The 11th edition of the World Health Organization's International Classification of Diseases (ICD) has been developed in close contact with the International Headache Society classification committee and is in fact an abbreviated version of ICHD-3. The principles of the ICHD have also been used by the International Association for Study of Pain in developing a pain classification now included in ICD-11. The many points of discussion of each of the three editions are still relevant for headache experts and all those who care for headache patients. CONCLUSION:Headache classification is a living and developing discipline of research. Here, the gradual expansion and refinement of the classification through 3 different editions are discussed with a view to present day relevance.