visual snow syndrome

Q: What is visual snow syndrome?

Answer: Continuous, tiny, flickering dots throughout the visual field of both eyes 

Visual snow syndrome is classically described as reminiscent of the "static" on old, mistuned TVs with continuous, tiny, flickering dots throughout the visual field of both eyes. It is a different entity from symptoms of migraine (see reference # 4) or its aura, though the International Headache Society (IHS) still describes it under the complications of migraine.  Also, it is different from the visual snow from hаllսϲiոatiοոѕ persisting after ingestion of a hallucinogen.

The visual snow syndrome now has an official definition from the IHS:

1. Dynamic, continuous, tiny dots across the entire visual field, persisting for more than three months

2. Additional visual symptoms of at least two of the following four types:

• Palinopsia 
• Enhanced entoptic phenomena
• Photophobia to sunlight and bright screens
• Nyctalopia 

3. Symptoms are not consistent with typical migrаinе visual aura

4. Symptoms are not better accounted for by another disorder

The etiology is not well understood, though it is probably due to hyperexcitability, which drives thalamocortical dysrhythmia. These patients on FDG-PET scans usually have more hypermetabolism in the lingual gyri than control subjects.

The syndrome usually appears in the third decade of life and has been reported in children. Antiepiletics may help.

#neurology

References:

1. International Headache Society ICHD-3. https://ichd-3.org/appendix/a1-migraine/a1-4-complications-of-migraine/a1-4-6-visual-snow/ (Accessed on January 19, 2025).

2. Bou Ghannam A, Pelak VS. Visual Snow: a Potential Cortical Hyperexcitability Syndrome. Curr Treat Options Neurol 2017; 19:9.

3. Lauschke JL, Plant GT, Fraser CL. Visual snow: A thalamocortical dysrhythmia of the visual pathway? J Clin Neurosci 2016; 28:123.

4. Schankin CJ, Maniyar FH, Sprenger T, et al. The relation between migraine, typical migraine aura and "visual snow". Headache 2014; 54:957.

5. Gronseth GS, Woodroffe LM, Getchius TSD. Clinical Practice Guideline Process Manual, American Academy of Neurology, St. Paul, MN 2011. p.1.