Somatosensory perception in Visual Snow Syndrome: a comparison to age-, sex- and migraine-matched controls using Quantitative Sensory Testing - no evidence of altered somatosensory thresholds.

BACKGROUND: Visual Snow Syndrome (VSS) is characterized by persistent, television noise like visual disturbances, accompanied by other visual and non-visual symptoms. Although VSS is recognized as a clinical entity, its underlying mechanisms remain poorly understood. One hypothesis is that VSS may involve increased sensory "noise" due to impaired sensory filtering, which could extend to non-visual modalities, such as somatosensory perception. This study aims to evaluate somatosensory perception in VSS using Quantitative Sensory Testing (QST), an established method to quantify sensory perception regarding different qualities such as heat, cold, touch and nociceptive stimuli. METHODS: Thirty-six patients with VSS and thirty-nine controls matched for age, sex and migraine were included. Given the high prevalence of migraine in VSS patients, controls were matched for migraine for its potentially confounding effects in QST. We used the standard QST protocol to assess somatosensory perception, which we performed on the dorsum of the right hand. In addition to assessing sensory sensitivity, we also calculated intraindividual variability in test results (as a measure of "somatosensory noise"). For subgroup analysis both groups were divided by migraine status using a two-way ANOVA. RESULTS: In demographics, migraine onset was earlier in VSS than in controls (11.7 years ± 6.5 vs. 17.8 years ± 9.1; p = 0.030), additionally migraine with visual aura was significantly more often present in VSS than in controls (80% vs. 23%; p = 0.017). Our two-way ANOVA analysis revealed no statistically significant main effect or interaction of migraine or VSS on QST parameters. Results for intraindividual variability were similar, except for a significant interaction between VSS and migraine on vibration detection threshold (F(1, 70) = 18.909, p < 0.001, partial η² = 0.21). CONCLUSIONS: These results suggest that VSS, despite being recognized as a multisensory disorder, seems to have no direct impact on somatosensory perception, supporting a predominantly higher-order condition of visual and sensory integration rather than a primary somatosensory dysfunction. Additionally, VSS patients showed significantly earlier migraine onset compared to controls, suggesting shared underlying mechanisms with migraine with aura, which would require further investigations.