Chronic daily headache in a tertiary care population: correlation between the International Headache Society diagnostic criteria and proposed revisions of criteria for chronic daily headache.

The International Headache Society (IHS) has been criticized for its approach to classification of chronic daily headache (CDH); Silberstein and Lipton criteria provide an alternative to this approach. The aim of this study is to apply the alternative diagnostic approaches to a sample of CDH patients consulting in specialty care. Our sample consisted of 638 patients with CDH. Patients were classified according to both classification systems. Patients were predominantly female (65.0%), with ages ranging from 11 to 88 years. According to the Silberstein and Lipton classification, we found eight different diagnoses. The most common diagnosis was chronic migraine (87.4%), followed by new daily persistent headache (10.8%). Just six patients had chronic tension-type headache (CTTH). Applying the IHS criteria we found 14 different diagnoses. Migraine was found in 576 (90.2%) patients. CTTH occurred in 621 (97.3%), with only 10 (1.57%) having this as the sole diagnosis. We conclude that both systems allow for the classification of most patients with CDH when daily headache diaries are available. The main difference is that the IHS classification is cumbersome and requires multiple diagnoses. The Silberstein and Lipton system is easier to apply, and more parsimonious. These findings support revision of the IHS classification system to include chronic migraine.