Occipital cortex and cerebellum gray matter changes in visual snow syndrome

Abstract

Objective: To determine whether regional gray and white matter differences characterize the brain of patients with visual snow syndrome, a newly defined neurologic condition, we used a voxel-based morphometry approach.

Methods: In order to investigate whole brain morphology directly, we performed an MRI study on patients with visual snow syndrome (n = 24) and on age- and sex-matched healthy volunteers (n = 24). Voxel-based morphometry was used to determine volumetric differences in patients with visual snow. We further analyzed cerebellar anatomy directly using the high-resolution spatially unbiased atlas template of the cerebellum.

Results: Compared to healthy controls, patients with visual snow syndrome had increased gray matter volume in the left primary and secondary visual cortices, the left visual motion area V5, and the left cerebellar crus I/lobule VI area. These anatomical alterations could not be explained by clinical features of the condition.

Conclusion: Patients with visual snow syndrome have subtle, significant neuroanatomical differences in key visual and lateral cerebellar areas, which may in part explain the pathophysiologic basis of the disorder.

Figure 1. Gray matter (GM) volume increase in the left visual cortex in visual snow syndrome

Left primary visual cortex increases in GM volume in patients with VSS with respect to controls (x = −2, y = −98, z = 3; k = 594; p = 0.007 uncorrected, p = 0.06 family-wise error). Results are from whole-brain analysis; GM volume differences between groups are outlined over T1 images. Bar represents T values.

Figure 2. Changes in cerebellar gray matter (GM) volume in visual snow syndrome (VSS)

(A) Area of cerebellar gray matter volume increase in patients with VSS (x = −12, y = −62, z = −23; k = 25; p = 0.02 family-wise error). GM volume differences between groups are outlined over parcellated cerebellar T1 images. Bar represents T values. (B) Cerebellar flatmap of plotted T values from patients with VSS with respect to controls (obtained from SUIT within SPM12), with labels for anatomical regions. Bar represents T values.

Figure 3. Summary of cortical volumetric changes in patients with visual snow syndrome, as shown by voxel-based morphometry

Render illustration of the 3 brain regions of increased gray matter volume in patients with visual snow syndrome with respect to healthy controls. Left V1 cluster is illustrated in green; left V5 cluster in blue; left cerebellum cluster in red. For statistical values of each area, see the text. Image was created in MRICroGL and superimposed on standard brain template.