Is Visual Snow a Migraine Aura?
Visual snow looks like falling snow, static on a TV, or tiny dots in all or part of the visual field. It can be considered to be a form of visual hallucination, and can also present as a migraine phenomenon. The technical term for this is Positive Persistent Visual Disturbance. Persisting visual snow in a migraineur is also called persistent aura without infarction.
Visual snow can also be a manifestation of Hallucinogen Persisting Perception Disorder, following the use of hallucinogen drugs (LSD, ecstasy, psychedelic mushrooms, and others). In HPPD, other visual distortions are frequent, including starbursts, afterimages, palinopsia (trails on moving objects), and others.
A prospective study of 120 patients with persistent visual snow, substance abuse was present in 40%. This study found that in addition to visual snow, many patients also experienced floaters (73%), persistent after-images (63%), photophobia (54%), flashes (44%), moving objects leaving trails (palinopsia - 48%), difficulty seeing at night (58%), "little cells that travel on a wiggly path" (57%)and "swirls with eyes closed" (41%).
A more recent study has found that on PET studies, subjects with visual snow had evidence of a brain dysfunction (a hypermetabolic lingual gyrus) that is different from what is found in migraine. Of 120 patients with “visual snow,” 70 patients also had migraine and 37 had typical migraine aura. The migraineurs with visual snow were more likely to experience palinopsia (trailing objects or afterimages) as well.
For the migrainous form of persisting visual snow, acetazolamide has been proposed, as well as valproate, topiramate, and lamotrigine. Visual snow related to HPPD has been managed with pharmaceutical as well as non-pharmaceutical strategies.
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Post updated 6/17/14