Abstract
In migraine, abnormal visual cortical excitability between headaches could predispose to cortical spreading depression and visual aura. Prior fMRI studies comparing migraineurs with aura (MWA) to controls have produced contradictory results. Using larger sample sizes and carefully matched groups, we tested if primary visual cortex (V1) has increased BOLD responsiveness to photic stimulation in MWA patients compared to migraineurs without aura (MWoA) and controls.
BOLD EPI (160 TRs, 3 mm voxels, TR = 3, at 3 Tesla) was collected while subjects viewed a 5 Hz flickering checkerboard alternating with darkness. Subjects performed an attention task at fixation. There were 13 subjects in each group (each group age = 34.5 ± 6 SD, 11 women/2 men). The average amplitude of BOLD response (discarding phase) was obtained for each subject within a V1 region of interest defined anatomically using cortical surface topology (FreeSurfer; O Hinds, 2008). Two-tailed t-tests compared the responses between the populations.
Within V1, BOLD responses were significantly larger in MWA as compared both to controls (p < 0.017) and MWoA (p < 0.038). This effect was specific to V1: within the occipital lobe excluding V1, there were no differences between the groups (all p′s > 0.1). This effect was specific to patients with aura, as migraine without aura (MWoA) did not differ from controls in any region.
Consistent with the presumed mechanism of photic sensitivity in migraine, a larger BOLD response to light was seen in patients with aura within area V1. As BOLD fMRI measures a neuro-vascular response, we cannot attribute the difference in this study to a larger neural response or greater vascular reactivity.