Fig. 1

T-statistical map of significant clusters in the voxel-based two sample t tests of ¹⁸F-FDG PET of visual snow syndrome patients (VSS) versus healthy controls (CON). A Red–yellow scale shows increased glucose metabolism in VSS compared to CON. The color bar represents t values for SPM group comparison at p_FWE < 0.05 corrected for multiple comparisons on voxel level (k_ext = 200 voxels). B Surface rendering with hypermetabolic (VSS > CON; purple: p_FWE < 0.05; red: p_{height,uncorrected} < 0.001) and hypometabolic (VSS < CON; blue: p_{height,uncorrected} < 0.001) regions in VSS compared to CON. L = left, R = right. C Plot of the effect in the visual cortex (left; peak voxel Talairach coordinate [− 15, − 75, 17 = L calcarine], see Table 2) and medial temporal cortex (right; peak voxel Talairach coordinate [− 12, − 38, − 5 = L parahpc gyrus], see Table 2) shows no overlap; CON scan number 1–15 and VSS 16–22