Repetitive transcranial magnetic stimulation for visual snow syndrome: symptoms relief and changes in brain dynamics. A case report

Visual Snow Syndrome (VSS) is a rare neurological condition characterized by continuous static and dynamic visual dots that impair vision, despite preserved visual acuity. Its pathophysiology is still debated, but it is believed to involve cortical hyperexcitability and dysfunctional connectivity within visual processing networks. Pharmacological treatments have shown limited efficacy. In this work, we report the case of an 18-year-old female with VSS refractory to lamotrigine and topiramate, who underwent a novel non-invasive brain stimulation treatment using low-frequency (1-Hz) repetitive transcranial magnetic stimulation (rTMS) targeting the bilateral superior parietal lobule (SPL). The rTMS intervention consisted of ten daily sessions (5 days/week), with stimulation intensity individualized according to the phosphene threshold (PT). Clinical evaluations, fMRI, and EEG were performed before and after treatment. During the intervention, the PT progressively increased throughout treatment days. Post-intervention, the patient reported subjective clinical improvement. Furthermore, fMRI data showed reduced resting-state functional connectivity (rs-FC) between the SPL and the lingual gyrus (LG) bilaterally, while resting-state EEG power spectral density (PSD) showed a decrease in gamma-band power, particularly in the parieto-occipital region. These findings support the hypothesis that inhibitory rTMS may help restore physiological neural activity in visual processing networks, thereby alleviating VSS symptoms.