Visual Snow: a Potential Cortical Hyperexcitability Syndrome

The purpose of this review is to provide an overview of visual snow (VS) and provide information regarding current treatment options for VS. Visual snow (VS) is a rare disorder manifesting with a persistent visual phenomenon of seeing numerous tiny snow-like dots throughout the visual field, and it can cause debilitating visual and psychological consequences. It is emerging as a disorder separate from, but associated with, migraine visual aura, and neuronal cortical hyperexcitability is being considered as a theoretical mechanism for the persistent-positive visual symptoms. There are few studies that have investigated the treatment of VS, but as our understanding of this entity begins to change, we expect that new treatment approaches and treatment trials will emerge in the next decade. Currently, our approach is to consider pharmacologic treatment for all patients with VS who report decreased quality of life as a result of VS. Resolution of the disorder is difficult to accomplish with treatment, but in our experience, even when symptom intensity is simply reduced, many patients find that there is an improvement in their quality of life that is beneficial. Our preferred treatment options include: (1) oral lamotrigine with a slow increase from 25 mg daily to a maintenance dose of 200–300 mg daily in divided doses as tolerated, and this is typically achieved by advancing the dose in increments of 25–50 mg weekly following the first 2 weeks of therapy; (2) oral acetazolamide with an initial dose of 250 mg daily followed by a slow increase over 1–2 weeks to a total of 1000 mg daily in divided doses, and higher doses can be tolerated by some without increasing the risk-benefit ratio; or (3) oral verapamil long-acting at 120–240 mg daily, and if side effects limit the dose the can be initiated, then lower doses with short-acting verapamil two or three times daily can be substituted until higher doses with the long-acting formula can be tolerated. By initiating drug treatments with low doses and slowly increasing over 1 to 4 weeks, tolerability and compliance improves and allows patients to realize the full benefits of treatment. The proposed mechanisms of microstructural cortical abnormalities and hyperexcitability as a cause of VS may lead to new treatment approaches in the future. Until such a time, medications reported to relieve persistent visual phenomena of migraine and visual aura of migraine are treatment options worth considering and these are reviewed for that purpose. Although clinical trials for the treatment of visual snow are lacking due to the rarity of the disorder, medications reviewed here should be considered for use in patients with VS who experience an impact on their quality of life. Theoretical mechanisms that lead to cortical hyperexcitability are being investigated and could lead to new treatment options. In the meantime, medications may provide benefits in this disabling condition.