Abstract
ObjectiveVisual snow (VS) is a distressing, life-impacting condition with persistent visual phenomena. VS patients show cerebral hypermetabolism within the visual cortex, resulting in altered neuronal excitability. We hypothesized to see disease-dependent alterations in functional connectivity and gray matter volume (GMV) in regions associated with visual perception.MethodsNineteen patients with VS and 16 sex- and age-matched controls were recruited. Functional magnetic resonance imaging (fMRI) was applied to examine resting-state functional connectivity (rsFC). Volume changes were assessed by means of voxel-based morphometry (VBM). Finally, we assessed associations between MRI indices and clinical parameters.ResultsPatients with VS showed hyperconnectivity between extrastriate visual and inferior temporal brain regions and also between prefrontal and parietal (angular cortex) brain regions (p < 0.05, corrected for age and migraine occurrence). In addition, patients showed increased GMV in the right lingual gyrus (p < 0.05 corrected). Symptom duration positively correlated with GMV in both lingual gyri (p < 0.01 corrected).ConclusionThis study found VS to be associated with both functional and structural changes in the early and higher visual cortex, as well as the temporal cortex. These brain regions are involved in visual processing, memory, spatial attention, and cognitive control. We conclude that VS is not just confined to the visual system and that both functional and structural changes arise in VS patients, be it as an epiphenomenon or a direct contributor to the pathomechanism of VS. These in vivo neuroimaging biomarkers may hold potential as objective outcome measures of this so far purely subjective condition.
Highlights
MATERIALS AND METHODSVisual snow is a visual disturbance occurring in individuals with normal ophthalmic findings
Referring to the accepted notion that visual snow (VS) results from disturbed visual processing, this study investigates changes in resting-state functional magnetic resonance imaging (fMRI) of patients with VS compared to healthy control (HC) within and outside the visual cortex
The main findings of this study were hyperconnectivity in the visual and prefrontal cortex and higher gray matter volume (GMV) in the right lingual gyrus in patients with VS compared to controls
Summary
Visual snow is a visual disturbance occurring in individuals with normal ophthalmic findings. It usually affects young adults and is characterized by the continuous perception of innumerable flickering dots (Schankin et al, 2014a). When associated with additional visual symptoms, it is referred to as “VS syndrome” (Schankin et al, 2014a; Puledda et al, 2018) The latter involves VS as the main symptom with at least two additional visual symptoms from the following four categories: palinopsia, enhanced entoptic phenomena, photophobia, and nyctalopia. Regarding migraine with or without aura (Schankin et al, 2014a,b), there is a suspected overlap in disease mechanism (Puledda et al, 2018), which represents one of the major challenges in VS research
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