Diagnosis of migraine: empirical analysis of a large clinical sample of atypical migraine (IHS 1.7) patients and proposed revision of the IHS criteria.

The International Headache Society (IHS) diagnostic criteria for headache improved the accuracy of primary headache diagnoses, including migraine. However, many migraineurs receive an 'atypical migraine' diagnosis according to the IHS nosology (IHS 1.7), indicating that they approximate but do not fully meet all IHS criteria. This study characterized and sub-classified patients with atypical migraine. Within a clinical sample of 382 headache sufferers, 83 patients met IHS criteria for 'atypical migraine'. Patients receiving the IHS 1.7 designation did not converge to form a homogeneous group. Rather, distinct and clinically relevant subgroups were empirically derived (e.g. migraine with atypical pain parameters, brief migraine, chronic migraine). The results call for revisions of the IHS diagnostic criteria for migraine that would minimize the number of patients receiving an atypical diagnosis. Revisions would include decreasing the minimum headache duration criteria from 4 h to 2 h, and developing a classification for 'chronic migraine' for migraine greater than 15 days per month. The proposed revision provides a means of diagnosing the daily and near-daily headache commonly observed in clinical populations.