Walsh & Hoyt: Classification of Headache: International Headache Society Criteria

Headache may occur in isolation or as part of a symptom complexthe primary headache syndromes, or may be part of an underlying condition, such as brain tumor or stroke the secondary headache syndromes. Management of secondary headache syndromes is largely determined by the underlying structural or metabolic disorder responsible for the generation of pain. Management of primary headache syndromes, however, is dependent upon accurate diagnosis and classification, which then serves to guide therapy. Prior to 1988, there were no standardized headache classification systems with operational rules and uniform nomenclature. In 1988, the International Headache Society (IHS) instituted a classification system that has become the standard for headache diagnosis. The IHS criteria have received broad international support, and the principles of the system have been included in the International Classification of Diseases (ICD). The IHS criteria have established uniform terminology and consistent diagnostic criteria for a range of headache disorders; in turn, this has facilitated epidemiological studies and clinical trials that provide the basis for current research and treatment guidelines. The second edition of the IHS classification was recently completed and follows the same principles as the first edition. Several headache syndromes that did not have sufficient valid evidence (e.g., carotidynia) have been eliminated, and new headache syndromes (e.g., hemicrania continua) have been added. As in the first edition, the classification draws upon all forms of available evidence, including clinical description, longitudinal and epidemiological studies, treatment results, genetics, neuroimaging, and pathophysiology. That the classifications remain largely descriptive, in part reflects the subjective nature of pain symptoms. As research identifies more specific, objective markers for pain disorders, the IHS criteria will likely incorporate these findings in future editions. At this point, however, the IHS classification system remains an invaluable source of information and the primary reference for any physician evaluating and managing patients with head and facial pain.