A new study published in The Journal of Headache and Pain investigated whether Visual Snow Syndrome (VSS) affects the way the body detects and processes physical sensations such as temperature, touch, vibration and pain.
The study, titled Somatosensory perception in Visual Snow Syndrome: a comparison to age-, sex- and migraine-matched controls using Quantitative Sensory Testing, explored whether the sensory disturbances associated with VSS extend beyond vision into the body’s somatosensory system.
The findings showed no significant overall differences in somatosensory perception between people with VSS and matched controls. The researchers suggest that VSS may therefore involve differences in higher-order visual and sensory processing and integration, rather than a fundamental problem with the body’s ability to detect physical sensory input.
Why Study Somatosensory Processing in Visual Snow Syndrome?
Visual Snow Syndrome is characterized by persistent visual snow, often described as countless tiny, flickering dots across the visual field. It can also involve additional visual symptoms such as palinopsia, photophobia, enhanced entoptic phenomena and nyctalopia, as well as non-visual conditions and symptoms including migraine and tinnitus.
Because some features of VSS have been associated with altered sensory processing, researchers have questioned whether the condition could involve a broader difficulty filtering sensory information.
One hypothesis is that the persistent visual “noise” experienced in VSS may be related to impaired sensory filtering. If this process affects more than vision, differences might also be detectable in somatosensory perception, which includes how the nervous system processes sensations such as heat, cold, touch, vibration, pressure and pain.
The researchers designed this study to investigate that possibility.
How Was the Study Conducted?
The study included 36 people with Visual Snow Syndrome and 39 control participants. The groups were matched for age, sex and migraine history.
Matching for migraine was particularly important because migraine is common among people with VSS and can itself influence sensory processing.
Researchers used Quantitative Sensory Testing (QST), a standardized method used to measure how people perceive different types of physical sensory stimuli.
Testing was performed on the back of the participants’ right hands and assessed several types of sensation, including:
- Cold detection
- Warm detection
- Cold pain
- Heat pain
- Light touch
- Pinprick sensitivity
- Pressure pain
- Vibration
- Responses to repeated painful stimulation
The full protocol assessed 13 sensory parameters across seven tests.
The researchers also repeated the testing so they could examine how much each participant’s responses varied. This was used as a possible measure of “somatosensory noise,” or inconsistent processing of sensory information.
What Did the Researchers Find?
The primary finding was that people with Visual Snow Syndrome did not show major abnormalities in basic somatosensory perception compared with the control group.
There were no significant overall differences in the participants’ abilities to detect touch, warmth, cold or vibration. The researchers also found no significant differences in pain thresholds or sensitivity after correcting for multiple statistical comparisons.
This means that, based on the sensory tests used in this study, people with VSS generally detected physical sensations similarly to people without VSS.
Researchers also examined whether responses were more variable in people with VSS, which could have supported the idea of increased sensory “noise.”
Again, they found no consistent pattern of increased variability across the sensory tests. One interaction involving vibration detection remained statistically significant, but the researchers noted that this may have been related to the small subgroup sizes rather than representing a broader VSS-related sensory abnormality.
What Do These Findings Mean for Visual Snow Syndrome?
The findings help researchers further examine where sensory processing differences in VSS may be occurring.
The fact that basic somatosensory detection appeared largely normal suggests that VSS may not involve a widespread dysfunction in the nervous system’s ability to detect incoming physical sensations.
Instead, the researchers suggest that VSS may be more closely associated with higher-order sensory processing and integration.
Previous research cited in the study has identified differences in activity and connectivity within brain regions and networks involved in visual processing, attention, salience and sensory integration. According to the authors, the current findings are consistent with the possibility that VSS involves how sensory information is filtered, integrated or interpreted by higher-level brain networks, rather than a problem with primary somatosensory detection itself.
In simpler terms, the study suggests that the nervous system may be receiving basic sensory information normally, while differences could occur later in the way that information is processed or integrated.
Importantly, normal results on these somatosensory tests do not mean that the sensory experiences associated with VSS are absent. Rather, the findings help narrow down which parts of sensory processing may or may not be involved in the condition.
An Additional Finding Involving Migraine
The researchers also identified an interesting secondary finding involving migraine.
Among participants with migraine, those with VSS reported that their migraines began at an average age of 11.7 years, compared with 17.8 years among controls with migraine. Migraine with visual aura was also significantly more common among the VSS participants with migraine.
The authors note that this could point toward shared mechanisms between VSS and migraine with aura, potentially involving processes such as cortical hyperexcitability. However, they emphasize that this interpretation remains speculative and requires further investigation using larger groups that are specifically matched for migraine aura.
Why Is This Research Important?
Understanding Visual Snow Syndrome requires researchers to determine not only what may be different in VSS, but also which sensory processes appear to remain intact.
This study provides evidence that basic somatosensory thresholds for temperature, touch, vibration and pain appear largely normal in people with VSS. That finding helps refine current theories about the condition and suggests that future research may benefit from focusing more closely on higher-order sensory integration, filtering and brain network function.
The study also supports the idea that Visual Snow Syndrome may be better understood by examining how different areas and networks of the brain communicate and process sensory information, rather than looking only for abnormalities in the eyes or in basic sensory detection.
Continuing to Understand the Mechanisms Behind VSS
Overall, the researchers concluded that people with Visual Snow Syndrome showed normal somatosensory thresholds and largely normal variability in their responses.
The findings support the current understanding of VSS as a condition that may predominantly involve visual and sensory integration at a higher level of processing, without substantial involvement of the primary somatosensory system.
For the Visual Snow Syndrome community, studies like this help build a more precise understanding of the condition by showing both where differences may exist and where sensory function appears to remain normal.
As research continues, identifying the specific neural processes involved in Visual Snow Syndrome may help guide future studies examining its underlying mechanisms and ultimately contribute to a clearer understanding of VSS.