What is the cause of Visual Snow Syndrome?

The exact cause of Visual Snow Syndrome is as yet unknown. More research and funding are needed to find out more. However, thanks to research conducted in recent years, there are indications that there is a hyperexcitability of the brain.

Although not enough is yet known about the origin, it is thought that the persistent visual phenomena are caused by constantly reverberating CSDs (ongoing brain process), possibly combined with a steady-state hyperexcitability of the visual cortex. The longer the visual phenomena exist, the more permanent the phenomena might become due to structural reorganisation of certain brain areas, which would explain the persistence of the symptoms (https://www.lumc.nl/sub/5035/att/1257745). Another study indicates that it may be due to increased excitability of brain cells in the right gyrus lingualis and the left lobus anterior cerebelli. In August 2020, a study by neurologists showed that Visual Snow Syndrome patients have subtle, significant neuroanatomical differences in the major visual and lateral cerebellar areas, which may partially explain the pathophysiological basis of the condition. In the same year, another study by neurologists demonstrated hypermetabolism and cortical volume increase in Visual Snow Syndrome patients in the extrastriate visual cortex at the junction of the right lingual and fusiform gyrus.  There was hypometabolism in the right superior temporal gyrus and the left inferior parietal lobule. Patients had increases in grey matter volume in the temporal and limbic lobes and decreases in the superior temporal gyrus. The corresponding structural and functional changes highlight the relevance of the visual association cortex for VSS. This gives the clinical impression that the disorder extends beyond the visual system.