A diagnostic sign in migraine?
At the bedside it was noted that, after ocular fundoscopy, patients with migraine complained more often of an after-image than did non-migraineurs. This phenomenon was then investigated in consecutive patients attending a general neurology outpatient clinic. The relative risk for the diagnosis of migraine in patients reporting an after-image was 2.91 (95% confidence interval 1.96 to 4.34), and the sensitivity, specificity and positive predictive value of this observation for the diagnosis of migraine were 0.63, 0.75 and 0.55 respectively. After-images were equally likely to be reported by migraineurs with and without aura, and by patients with migraine equivalents. The after-image phenomenon probably reflects the heightened sensitivity to visual stimuli of patients with migraine. Although a diagnosis of migraine is primarily established by the patient's history, the presence of an after-image following ocular fundoscopy may support this diagnosis.