Adie's tonic pupil secondary to migraine.

A 46-year-old woman observed transient unilateral mydriasis during a classic migraine attack. One week later she experienced a similar episode after which anisocoria was persistent. Subsequent examination showed the clinical and pharmacologic features of a postganglionic parasympathetic paresis (Adie's tonic pupil). This case confirms the hypothesis that transient mydriasis accompanying migraine is due to interruption of parasympathetic innervation rather than sympathetic overactivity.