The international classification of headache disorders, 2nd edn (ICDH-II)
- 1Department of Neurology, Glostrup University Hospital, 2600 Glostrup, Denmark
- 2Division of Neuroscience, Imperial College London, London, UK
- Correspondence to: J Olesen Department of Neurology, Glostrup University Hospital, 2600 Glostrup, Denmark; jeolglostruphosp.kbhamt.dk
Better classification of headache disorders enables better headache research, understanding of headache, communication, and, ultimately, management of a set of disabling neurological disorders
In the past, many have viewed the primary headache disorders as a continuum of which each is part. Better headache classifications have prompted slowly developing awareness of the existence of many discrete entities amongst these disorders. This in turn has contributed not only to their better recognition in clinic (and therefore management) but also to nosological research that has produced better characterisation of many headache disorders.
THE ORIGINS OF ICHD-II
The first proposals for the classification of headache disorders were put forward in the 1960s, one from an ad hoc committee of the US National Institutes of Health1 and another, quite similar, from the Research Group on Migraine and Headache of the World Federation of Neurology.2 Both proposals merely listed the few headache disorders that were accepted at that time, and gave short descriptions of them rather than diagnostic criteria. The major advance, and the first internationally acceptable—and clinically useful—classification system, came in 1988 when the Headache Classification Committee of the International Headache Society (IHS) published what is now referred to as “The International Classification of Headache Disorders, 1st edition”.3
Several years of work involving more than 100 international headache experts resulted in a much more comprehensive and hierarchical classification of headache types and subtypes, both primary and secondary, using up to four digits to designate the subordinate levels. Explicit diagnostic criteria for at least most major headache disorders were also set out for the first time. This classification became universally accepted,4–6 and was translated into more than 20 languages. No competing headache classifications have existed since that time.
Although the diagnostic criteria were, in many cases, based on the opinions of experts rather than on …
