Validation of the classification of migraine without aura (IHS A1.1) proposed in ICHD-2

This study attempts to validate the alternative criteria for classification of migraine without aura (International Headache Society [IHS] A1.1) proposed in the appendix of The International Classification of Headache Disorders, 2nd edition. This method uses at least two of the associated symptoms (nausea, vomiting, photophobia, phonophobia, and osmophobia) in category D of the IHS classification.

In the appendix of The International Classification of Headache Disorders, 2nd edition, an alternative method of classification of migraine without aura is proposed. This method of classification has never been validated.

A total of 1480 consecutive headache patients in a tertiary care setting were evaluated at first visit. Headache-associated features, such as intensity, lifetime duration, frequency per month, duration, triggers, prodrome, percentage recurrence, and postdrome frequency, were recorded. In addition, medication satisfaction, acute and monthly disability, grading of headache days, sleep normality, mood, and habits were documented.

Of the 1480 patients, 901 were initially classified as having migraine IHS 1.1. Using the proposed alternative method (IHS A1.1), 885 (98.2%) of these patients were reclassified as having migraine. The remaining 16 (1.8%) patients not classified had only nausea and none of the other specified associated symptoms. They also exhibited different characteristics from the IHS migraine population as a whole regarding their headache and other features.

This classification of migraine in a headache center population shows that the proposed use of any two of nausea, vomiting, photophobia, phonophobia, and osmophobia in category D of the classification may be a valid alternative method of classification. This study also demonstrates that the standard IHS methodology includes a very small group of patients who appear to be different from other migraine patients.