Authors' results suggest that all types of migraine are contraindications to oral contraceptives

EDITOR--Chang et al report that the odds ratios for ischaemic stroke in young women with classical migraine (with aura) and simple migraine (without aura) were similar.1 These findings are at odds with earlier studies, which reported increased risk primarily in migraine with aura.2 We note that the 95% confidence interval for ischaemic stroke in migraine without aura included unity (odds ratio 2.97 (95% confidence interval 0.66 to 13.5), unlike that for migraine with aura (3.81 (1.26 to 11.5). Therefore a lesser risk in migraine without aura is not excluded.

Another possible reason for the apparent discrepancy is that the authors failed to identify true aura. They characterised aura by at least one of the following symptoms just before or during the headache: visual disturbances or abnormalities of speech, skin sensation, or muscle power. Although their questionnaire was based on diagnostic criteria proposed by the International Headache Society, their questions were too non-specific.

Crucial characteristics of auras are symptoms and their duration and timing in relation to headache. Most (95%) are visual, typically starting as a flickering, uncoloured zigzag line in the centre of the visual field and gradually progressing laterally to the periphery of one hemifield, usually leaving a scotoma.3 Sensory or motor symptoms, if they occur, are usually also unilateral and rarely without associated visual symptoms.3 Auras typically last under one hour, resolving before the onset of headache. In contrast, the more general prodromal symptoms can precede the headache for several hours. …