Reduction in retinal nerve fiber layer thickness in migraine patients

Migraine is a common disorder and its pathogenesis remains still unclear. Several hypotheses about the mechanisms involved in the pathogenesis of migraine have been proposed, but the issue is still far from being fully clarified. Neurovascular system remains one of the most important mechanisms involved in the pathogenesis of migraine and it could be possible that hypoperfusion might involve other areas besides brain, including the retina. This is, for example, of particular interest in a form of migraine, the retinal migraine, which has been associated with hypoperfusion and vasoconstriction of the retinal vasculature. Although vasoconstriction of cerebral and retinal blood vessels is a transient phenomenon, the chronic nature of the migraine might cause permanent structural abnormalities of the brain and also of the retina. On this basis, a few studies have evaluated whether retina is involved in migraine patients: Tan et al. have not found differences in retinal nerve fiber layer (RNFL) thickness between migraine patients and healthy subjects, while Martinez et al. have shown that RNFL in the temporal retinic quadrant of migraineurs is thinner than in normal people. The aim of our study was to analyze if there are differences in retinal nerve fiber layer thickness between migraine patients and normal subjects by studying 24 consecutive migraine patients who presented at the Headache Center of our Neurological Department. Migraine diagnosis has been made according to the International Classification of Headache disorder (ICHD-II). Patients have been recruited according to strict inclusion criteria; then patients have undergone a complete ophthalmological examination at the Ophthalmological Department. All patients and controls who met the ophthalmological criteria have been examined with ocular coherence tomography spectral domain (OCT-SD) after pupillary dilation. OCT-SD is an optical system designed to acquire the retinal layer images simultaneously with fundus confocal images. The statistical analysis has been performed using the Statistical Package for Social Sciences program. The Student's t test has been used to compare numeric variables between migraine and control groups. p value >0.05 has been considered not significant. We have analyzed 40 female subjects, 24 included in the study group and 16 included in the control group. Two migraine patients have been excluded. No differences have been found in the visual acuity between the two groups. Comparing RNFLs of a single eye per person in the two groups, we have found that migraine patients showed significant reduction in the superior quadrants (p < 0.005). Also evaluating both eyes per person there was a significant difference in the same quadrant between the two groups (p < 0.05). The result of this present study show that migraine patients have RNFL thickness reduction in the superior retinal quadrant compared with normal subjects. It is important to underline that RNFL thickness measurement could be a new interesting technique to evaluate the evolution of migraine and perhaps to study if prophylactic treatment could reduce retinal abnormalities seen in migraine patients. OCT-SD is a simple exam that could be repeated and then used for evaluation of headache progression during the time. Our study shows that RNFLs thickness does not depend on illness duration and frequency.