Timothy C. Hain, MD, • Most recent update: March 7, 2021
Visual snow syndrome (VS) is mainly characterized by flickering, little dots in both visual fields. Diagnosis is based on patient reports and not better accounted for by another diagnosis. The exact pathophysiology of this syndrome is still unknown. (Yildiz et al, 2019)
VS is also associated with "palinopsia, photophobia, photopsias, entoptic phenomena, nyctalopia, and tinnitus." (White et al, 2018) The association of tinnitus with visual snow obviously suggests that it reflects a disorder broader than the visual system alone.
Visual snow is sometimes attributed to a persistant migraine aura. It has also been reported in a population who were exposed to hallucinogens. (Puledda et al, 2020) Tinnitus is a common accompaniment as well.
Metzler et al (2018) stated "Patients with visual snow syndrome frequently have comorbid migraine, but visual snow appears to be a separate entity from persistent migraine aura. "
Yildiz et al (2019) reported that "The loss of habituation and lower threshold for occipital cortex excitability were demonstrated electrophysiologically in VS patients. "
Eren et al (2018) reported that "Visual evoked potentials from patients with VS demonstrated increased N145 latency (in milliseconds, VS: 152.7 +/- 7.9 vs M: 145.3 +/- 9.8 vs C: 145.5 +/- 9.4; F = 3.28; p = 0.046) and reduced N75-P100 amplitudes (in microvolts, VS: 7.4 +/- 3.5 vs M: 12.5 +/- 4.7 vs C: 10.8 +/- 3.4; F = 3.16; p = 0.051). " This is somewhat of an opposite idea -- a decrease in responses rather than an increase.
Vandongen et al (2019) reported partial response to lamotrigine in about 80% of their 58 patients, but no response to valproate, acetazolamide, or flunarizine. One patient had a transient response to topiramate. Bou Ghanna and Pelak (2017) also favored lamotrigine (aiming for 200-300 mg/day), but also reported some success from acetazolamide and verapamil.