Authors: Sarah A. Aeschlimann, Antonia Klein, Frédéric Zubler, Christoph J. Schankin, Matthias Ert.
Introduction
Visual Snow Syndrome (VSS) affects visual, sensory, and attention networks in the brain. People with VSS constantly see flickering dots (like TV static) across their visual field and may also experience after-images, light sensitivity, trouble seeing in dim light, and eye floaters. Migraines and tinnitus are also common in these patients. About 2.2% of people may be affected by VSS. The condition is diagnosed based on symptoms, as there is no simple test or effective treatment yet.
VSS likely involves widespread brain networks, not just the visual system. Studying EEG microstates — brief patterns of brain activity — can help us understand how these networks behave in VSS.
Microstates are like tiny “snapshots” of how the brain is processing information. They last only milliseconds but reveal important details about how the brain operates during rest. In conditions like schizophrenia, depression, tinnitus, and migraine, these microstates often show abnormal patterns — so researchers wanted to see if the same is true in VSS.
Methods
Researchers analyzed EEG data from 21 people with VSS and 21 healthy controls. Participants were carefully matched by age, gender, and other factors. Anyone with epilepsy, major psychiatric illness, or neurological disease was excluded. Brain activity was recorded for 20 minutes while participants rested with their eyes closed.
Researchers analyzed four main types of microstates (Classes A–D), each linked to different brain functions:
- A: auditory and visual processing
- B: visual processing
- C: body awareness and emotion
- D: attention and thinking
Researchers measured how long each microstate lasted, how strong it was, how often it occurred, and how microstates transitioned from one to another.
Results
Compared to controls:
- People with VSS had shorter microstates (they didn’t last as long).
- Their brain activity was weaker (lower amplitude).
- They had more frequent transitions from microstate A (sensory processing) to B (visual processing), and fewer transitions from A to C (body awareness).
These findings suggest that brain networks in VSS are more unstable and less organized during rest. Even when looking only at people with VSS without migraines, the same differences were seen. This means the abnormalities are related to VSS itself — not just migraines.
Discussion
This study shows that people with VSS have unstable brain networks, especially in areas linked to processing sensory information. Shorter and weaker microstates suggest that the brain in VSS is not maintaining stable patterns of activity. This instability may contribute to the constant visual “static” experienced by patients. The differences in how microstates transition also point to disrupted sensory processing in VSS. Similar abnormalities in brain networks have been seen in other conditions like migraine and tinnitus — which supports the idea that VSS shares some underlying mechanisms with these disorders.
Future research could explore treatments that help “rebalance” these networks. For example, repetitive transcranial magnetic stimulation (rTMS) may help stabilize brain activity in VSS. Microstates may also serve as a useful biomarker — a measurable brain signature — for tracking VSS or testing new treatments.
