The epidemiology of migraine: a retrospective study in Italian emergency departments.

This study was conducted to measure the frequency of contact with emergency departments in Italy because of migraine, and to compare the initial diagnosi s of headache with the diagnosis after application of the International Headache Society (IHS) criteria. A retrospective observational method was used, consisting of an analysis of the records of patients admitted to nine Italian emergency departments during different 4-month periods in 1994. Comparison of the initial diagnosis with the diagnosis after application of the IHS diagnostic criteria was performed. More than 31 million emergency department contacts were reported in Italy during 1994. In the same year, 543 630 patients visited the nine emergency departments enrolled in the study, with 169 569 of these contacts occurring in the 4-month period analyzed in the study. We excluded from the analysis all cases of secondary headache fully recognized at the emergency department admission (ie, traumas, intracranial pathology, systemic diseases). The total number of patients included in our analysis was 1043 (0.6%). The 934 patients who could be fully evaluated were initially classified as having migraine; cluster headache; headache not otherwise specified; or diagnosed in the emergency department as suffering from headache, but reclassified by other departments as suffering from a different disease. After retrospective application of the IHS classification, the diagnostic distribution was modified, revealing that 18% of patients with migraine and 5% with cluster headaches had previously been classified as having headache not otherwise specified; a further 6% of cases with migraine and 0.4% of patients with cluster headache had previously been classified as having secondary headaches. The diagnosis of headache not otherwise specified was made with notable frequency, indicating the limits of emergency department logs and the difficulty in carrying out a retrospective analysis and reassessment of diagnosis. The majority (88%) of patients assessed had not taken drugs for headache in the 48 hours before the emergency department contact, suggesting that in Italy emergency departments are used instead of a visit to the general practitioner. Nonsteroidal anti-inflammatory drugs were the most frequently prescribed drugs in the emergency departments for this group of diagnoses. The research revealed, on the one hand, that headache is a numerically significant phenomenon in the emergency department setting and, on the other, the need to apply prospective designs to this kind of survey.