# Altered functional connectivity strength between structurally and functionally affected brain regions in visual snow syndrome

## TL;DR

This study shows that people with visual snow syndrome have altered brain connectivity, which is linked to how disruptive their symptoms feel.

## Contribution

The novel finding is altered functional connectivity in VSS patients, particularly involving the supramarginal gyrus and its relation to symptom severity.

## Key findings

- VSS patients showed higher connectivity between the supramarginal gyrus and lateral occipital cortex and fusiform.
- Reduced connectivity was found between the supramarginal gyrus and pallidum and between the parahippocampal gyrus and lateral occipital cortex.
- Altered connectivity correlated with the perceived disruptiveness of VSS symptoms.

## Abstract

Visual snow syndrome (VSS) is a neurological disorder that is predominantly characterized by persistent, dynamic visual disturbances, experienced across the entire visual field. Earlier research highlighted the significance of distinct brain regions, exhibiting alterations in both anatomical structure and functional characteristics. To further investigate the functional role of these regions, we examined the resting-state connectivity between these areas in individuals with VSS and the relation with VSS symptoms and oculomotor measures of visual processing. Forty patients with VSS (53% females; age = 33.2 ± 10.1 years; 22 with migraine) and 60 healthy controls (58% females; age = 32.0 ± 9.2 years) were scanned using 7 Tesla MRI system. High spatial and temporal resting-state (RS) functional (TR = 800 ms, 1.6 mm isotropic) and anatomical (MP2RAGE, 0.75 mm isotropic) images were acquired. Resting-state data were pre-processed (motion correction, temporal filtering and spatial smoothing), functional connectivity was calculated between regions of interest and compared between groups. Significant metrics were compared with VSS patients with and without migraine and correlated with oculomotor measures (prosaccade and anti-saccade latencies), number of VSS symptoms, self-rated VSS intensity and perceived disruptiveness. Compared to healthy controls, VSS patients demonstrated significantly higher connectivity between the supramarginal gyrus and lateral occipital cortex (P = 0.016) and fusiform (P = 0.007), lower connectivity between the supramarginal gyrus and pallidum (P = 0.032), as well as between the parahippocampal gyrus and lateral occipital cortex (P = 0.007), which related to higher perceived disruptiveness (P = 0.002, r = −0.489). No differences were found between VSS with and without migraine. This study revealed altered functional connectivity strength in individuals with VSS, suggesting stronger connectivity between cortical areas, particularly centred around the supramarginal gyrus, and disconnections with deep grey matter and temporal cortices, which associated with perceived disruptiveness of VSS.

Strik et al. found altered functional resting-state connectivity in people with visual snow syndrome, with increased cortical connectivity around the supramarginal gyrus and reduced connectivity with deep grey matter and temporal cortices, linked to the perceived disruptiveness of visual snow.

Graphical Abstract