The document discusses headache classification systems. It provides an overview of the old ad-hoc system and introduces the International Classification of Headache Disorders, 2nd edition (ICHD-2) which divides headaches into primary and secondary types. The ICD-9 code system is also discussed and revisions are proposed to bring it in line with current medical understanding and ICHD-2. New codes are suggested for cluster headaches, tension headaches, and other primary and secondary headache syndromes.

1. Headache Classification 2007 Stephen D. Silberstein, M.D., F.A.C.P. Director, Jefferson Headache Center, Professor of Neurology Thomas Jefferson University Hospital Philadelphia, Pennsylvania Past President American Headache Society

3. International Classification of Headache Disorders 2nd edition (ICHD-2)