Unsolved:Visual snow syndrome

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Short description: Visual impairment
"Visual snow" redirects here. For the display of noise in an analog video signal, see Noise (video). For the related phenomenon known as seeing stars, see Phosphene.
Visual snow syndrome
Other namesPersistent positive visual phenomenon,[1] visual static, aeropsia
refer to caption
Illustration of visual snow
SpecialtyNeurology, neuro-ophthalmology
SymptomsStatic and auras in vision, palinopsia, blue field entoptic phenomenon, nyctalopia, tinnitus
ComplicationsPoor quality of vision, photophobia, heliophobia, depersonalization and derealization[2]
Usual onsetVisual snow can appear at any time, but it commonly appears at birth, late teenage years, and early adulthood.
CausesUnknown,[3] hyperexcitability of neurons and processing problems in the visual cortex[4][5]
Risk factorsMigraine sufferer[6]
Differential diagnosisMigraine aura,[7] persistent aura without infarction, hallucinogen persisting perception disorder[8][9]
MedicationAnticonvulsants[7][3] (limited evidence and success)
FrequencyUncommon (understudied)

Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is persistent flickering white, black, transparent, or colored dots across the whole visual field.[7][4] It is distinct from the symptom of visual snow itself, which can also have several other causes; these cases are referred to as "VSS mimics."[10]

Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches.[11][12] The condition is typically always present and has no known cure, as viable treatments are still under research.[13] Astigmatism, although not presumed connected to these visual disturbances, is a common comorbidity. Migraines and tinnitus are common comorbidities that are both associated with a more severe presentation of the syndrome.[14]

The cause of the syndrome is unclear.[3] The underlying mechanism is believed to involve excessive excitability of neurons in the right lingual gyrus and left anterior lobe of the cerebellum. Another hypothesis proposes that visual snow syndrome could be a type of thalamocortical dysrhythmia and may involve the thalamic reticular nucleus (TRN). A failure of inhibitory action from the TRN to the thalamus may be the underlying cause for the inability to suppress excitatory sensory information.[4][6] Research has been limited due to issues of case identification, diagnosis, and the limited size of any studied cohort, though the issue of diagnosis is now largely addressed. Initial functional brain imaging research suggests visual snow is a brain disorder.[15]

Difference from visual snow

Visual snow – the symptom – may sometimes be a transient experience, and it is possible that it is a natural phenomenon, sometimes thought to be visible to many people if they focus on it.[16] In visual snow syndrome, however, visual snow is ever-present, regardless of lighting conditions and even when the eyes are closed.[17] In contrast to visual phenomena caused by migraines, which can last up to about an hour, static caused by visual snow syndrome lasts continuously for several months.[17]

If visual snow is persistent, continuous, and accompanied by other symptoms, such as entoptic phenomenon, palinopsia, photophobia and/or nyctalopia – it may indicate visual snow syndrome.[17] This syndrome is not just a phenomenon, but a neurological condition,[17] where a person experiences constant visual disturbances, regardless of lighting conditions.[17] Visual snow syndrome is linked to heightened neural sensitivity in the visual regions of the brain.[18] However, it is important not to confuse it with other causes of visual snow, sometimes referred to as VSS mimics.[10]

Signs and symptoms

Visual snow likely represents a clinical continuum, with different degrees of severity. The presence of comorbidities such as migraine and tinnitus is associated with a more severe presentation of visual symptoms.[14]

Non-visual symptoms may include difficulty concentrating, insomnia, frequent migraines, nausea, and vertigo.[19]

Diagnosis

Visual snow syndrome is usually diagnosed with the following proposed criteria:[20][21][14]

  • Visual snow: dynamic, continuous, tiny dots observed across the entire visual field at any time of the day, regardless of lighting conditions, persisting for more than three months.
    • The dots are usually black/gray on a white background and gray/white on a black background; however, they can also be transparent, white flashing, or colored.
  • Presence of at least 2 additional visual symptoms of the 4 following categories:
  • Symptoms are not consistent with typical migraine aura.
  • Symptoms are not better explained by another disorder (ophthalmological, drug abuse).


Mimics

The following conditions other than visual snow syndrome can also cause visual snow symptoms, and care must be taken not to confuse them with it:[10]

It must also be distinguished from migraine with visual aura.[10]

Common misconceptions

  • Eye pathologies or other neurological conditions can also be a cause of visual anomalies, including the appearance of visual static or other changes in perception. Additionally, psychological disorders, such as somatic disorders, could potentially contribute to these perceptual disturbances.[22][23]
  • Perceiving visual static, flickering, or graininess on monochrome colors, in the sky, or in darkness can be a normal phenomenon associated with neural noise, amplified in the absence of bright visual stimuli. This effect is related to how the eyes and brain process visual information in low-light conditions. In such environments, the visual system becomes more sensitive to light, amplifying noise or minor changes in visual signals. For example, in low-light conditions, rod photoreceptors, responsible for light perception in dim environments, are primarily activated. However, they cannot distinguish details or colors, leading to a blurred and grainy visual experience without clear contours. Cones, responsible for color perception and detail, are activated in brighter light, while rods provide vision in low-light conditions but with reduced precision. Therefore, the graininess perceived in the dark is a natural adaptation of our vision to photoreceptor limitations, not an indication of abnormality. It's important to note that the perception of such phenomena may vary among individuals due to differences in perception and sensitivity.[24][25][26]
  • Visual noise with closed eyes, also known as phosphenes, refers to the phenomenon where a person perceives random light or dark spots without an external light source. This effect is linked to the ongoing activity of the visual system, even with closed eyes, and can be caused by the electrical activity of neurons in the retina or visual cortex. Studies have shown that the visual system becomes more sensitive when the eyes are closed, which may lead to the perception of phosphenes or visual noise in the dark. These phenomena are a normal part of brain function as it continues processing information in the absence of external stimuli [27][28]

Comorbidities

Migraine and migraine with aura are common comorbidities. However, comorbid migraine worsens some of the additional visual symptoms and tinnitus seen in "visual snow" syndrome. This might bias research studies by patients with migraine being more likely to offer study participation than those without migraine due to having more severe symptoms. In contrast to migraine, comorbidity of typical migraine aura does not appear to worsen symptoms.[6]

Non-visual symptoms of visual snow can include depersonalization, derealization, depression, photophobia, and heliophobia in the individual affected.[2]

Patients with visual "snow" have normal equivalent input noise levels and contrast sensitivity.[29] In a 2010 study, Raghaven et al. hypothesize that what the patients see as "snow" is eigengrau.[29] This would also explain why many report more visual snow in low light conditions: "The intrinsic dark noise of primate cones is equivalent to ~4000 absorbed photons per second at mean light levels; below this the cone signals are dominated by intrinsic noise".[30][31]

Causes

The causes of VSS are not clear.[3] The underlying mechanism is believed to involve excessive excitability of neurons within the cortex of the brain,[4] specifically the right lingual gyrus and left cerebellar anterior lobe of the brain.[6]

Persisting visual snow can feature as a leading addition to a migraine complication called persistent aura without infarction,[32] commonly referred to as persistent migraine aura (PMA). In other clinical sub-forms of migraine headache may be absent and the migraine aura may not take the typical form of the zigzagged fortification spectrum (scintillating scotoma), but manifests with a large variety of focal neurological symptoms.[33]

Recent studies

  • In May 2015, visual snow was described as a persisting positive visual phenomenon distinct from migraine aura in a study by Schankin and Goadsby.[34]
  • In December 2020, a study[35] found local increases in regional cerebral perfusion in patients with visual snow syndrome.
  • In September 2021, two studies[36] found white matter alterations in parts of the visual cortex and outside the visual cortex in patients with visual snow syndrome.
  • In November 2023, a study[37] revealed that glutamate and serotonin are involved in brain connectivity alterations in areas of the visual, salience, and limbic systems in VSS. Importantly, altered serotonergic connectivity is independent of migraine in VSS, and simultaneously comparable to that of migraine with aura, highlighting a shared biology between the disorders.[38]

Treatments

It is difficult to resolve visual snow with treatment, but it is possible to reduce symptoms and improve quality of life through treatment, both of the syndrome and its comorbidities.[4] In some studies, lamotrigine as a treatment for visual snow syndrome only showed efficacy in 20% of patients, and in one study, patients using lamotrigine even reported worsening symptoms.[39] Medications that may be used include lamotrigine, acetazolamide, verapamil,[4] clonazepam, propranolol, and sertraline[40] but these do not always result in positive effects.[7][3] As of 2021, two ongoing clinical trials were using transcranial magnetic stimulation and neurofeedback for visual snow.[41][42]

A recent study in the British Journal of Ophthalmology has confirmed that common drug treatments are generally ineffective in visual snow syndrome (VSS). Vitamins and benzodiazepines, however, were shown to be beneficial in some patients and can be considered safe for this condition.[43]

References

  1. ↑ Licht, Joseph; Ireland, Kathryn; Kay, Matthew (2016). Visual Snow: Clinical Correlations and Workup A Case Series. Larkin Community Hospital. doi:10.13140/RG.2.1.2393.9443. https://www.researchgate.net/publication/303300977. Retrieved 3 September 2017. 
  2. ↑ 2.0 2.1 "Diagnostic Criteria | Visual Snow Initiative". 23 March 2023. https://www.visualsnowinitiative.org/diagnostic-criteria/. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Brodsky, Michael C. (2016) (in en). Pediatric Neuro-Ophthalmology. Springer. p. 285. ISBN 978-1-4939-3384-6. https://books.google.com/books?id=f_mODAAAQBAJ&pg=PA285. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Bou Ghannam, A; Pelak, VS (March 2017). "Visual snow: a potential cortical hyperexcitability syndrome". Current Treatment Options in Neurology 19 (3): 9. doi:10.1007/s11940-017-0448-3. PMID 28349350. 
  5. ↑ Bou Ghannam, A.; Pelak, V. S. (2017). "Visual Snow: A Potential Cortical Hyperexcitability Syndrome". Current Treatment Options in Neurology 19 (3): 9. doi:10.1007/s11940-017-0448-3. PMID 28349350. 
  6. ↑ 6.0 6.1 6.2 6.3 Schankin, CJ, Maniyar, FH, Sprenger, T, Chou, DE, Eller, M, Goadsby, PJ, 2014, The Relation Between Migraine, Typical Migraine Aura and "Visual Snow", Headache, doi:10.1111/head.12378
  7. ↑ 7.0 7.1 7.2 7.3 Dodick, David; Silberstein, Stephen D. (2016) (in en). Migraine. Oxford University Press. p. 53. ISBN 978-0-19-979361-7. https://books.google.com/books?id=Y-wmDAAAQBAJ&pg=PA53. 
  8. ↑ Schankin, C.; Maniyar, F.; Hoffmann, J.; Chou, D.; Goadsby, P. (22 April 2012). "Visual Snow: A New Disease Entity Distinct from Migraine Aura (S36.006)". Neurology 78 (Meeting Abstracts 1). doi:10.1212/WNL.78.1_MeetingAbstracts.S36.006. 
  9. ↑ Halpern, J (1 March 2003). "Hallucinogen persisting perception disorder: what do we know after 50 years?". Drug and Alcohol Dependence 69 (2): 109–119. doi:10.1016/S0376-8716(02)00306-X. PMID 12609692. 
  10. ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 10.10 10.11 10.12 10.13 10.14 10.15 Hang, Chenyue; Leishangthem, Lakshmi; Yan, Yan (2021). "Not All Cases of Visual Snows are Benign: Mimics of Visual Snow Syndrome". Neuropsychiatric Disease and Treatment 17: 3293–3300. doi:10.2147/NDT.S338111. ISSN 1176-6328. PMID 34785899. 
  11. ↑ "Visual snow syndrome - About the Disease - Genetic and Rare Diseases Information Center" (in en). https://rarediseases.info.nih.gov/diseases/12062/visual-snow-syndrome. 
  12. ↑ Puledda, Francesca; Schankin, Christoph; Goadsby, Peter J. (2020-02-11). "Visual snow syndrome: A clinical and phenotypical description of 1,100 cases" (in en). Neurology 94 (6): e564–e574. doi:10.1212/WNL.0000000000008909. ISSN 0028-3878. PMID 31941797. 
  13. ↑ Schankin, CJ; Goadsby, PJ (June 2015). "Visual snow--persistent positive visual phenomenon distinct from migraine aura". Current Pain and Headache Reports 19 (6): 23. doi:10.1007/s11916-015-0497-9. PMID 26021756. 
  14. ↑ 14.0 14.1 14.2 Puledda, Francesca; Schankin, Christoph; Goadsby, Peter (2020). "Visual snow syndrome. A clinical and phenotypical description of 1,100 cases.". Neurology 94 (6): e564–e574. doi:10.1212/WNL.0000000000008909. PMID 31941797. PMC 7136068. https://n.neurology.org/content/neurology/94/6/e564.full.pdf. Retrieved 2021-09-21. 
  15. ↑ Traber, Ghislaine L.; Piccirelli, Marco; Michels, Lars (February 2, 2020). "Visual snow syndrome: a review on diagnosis, pathophysiology, and treatment" (in en). Current Opinion in Neurology 33 (1): 74–78. doi:10.1097/WCO.0000000000000768. ISSN 1350-7540. PMID 31714263. https://journals.lww.com/10.1097/WCO.0000000000000768. 
  16. ↑ Costa, Rui Miguel; Campos, Pedro; Wiborg, Madalena; Rebôlo, Catarina; Wittmann, Marc; Kornmeier, Jürgen (2022). "Prevalence of visual snow and relation to attentional absorption". PLOS ONE 17 (11). doi:10.1371/journal.pone.0276971. ISSN 1932-6203. PMID 36342911. Bibcode: 2022PLoSO..1776971C. 
  17. ↑ 17.0 17.1 17.2 17.3 17.4 Sampatakakis, Stefanos N.; Lymperopoulos, Loukas; Mavridis, Theodoros; Karagiorgis, Georgios; Papadopoulos, Constantinos; Deligianni, Christina I.; Mitsikostas, Dimos D. (November 2022). "Visual snow: A systematic review and a case series". Cephalalgia: An International Journal of Headache 42 (13): 1409–1419. doi:10.1177/03331024221118917. ISSN 1468-2982. PMID 35945691. 
  18. ↑ Klein, Antonia; Schankin, Christoph J. (October 2021). "Visual snow syndrome, the spectrum of perceptual disorders, and migraine as a common risk factor: A narrative review". Headache 61 (9): 1306–1313. doi:10.1111/head.14213. ISSN 1526-4610. PMID 34570907. 
  19. ↑ Cleveland Clinic. (2024). Visual Snow Syndrome. https://my.clevelandclinic.org/health/diseases/24444-visual-snow-syndrome.
  20. ↑ Schankin, Christoph J.; Maniyar, Farooq H.; Digre, Kathleen B.; Goadsby, Peter J. (2014-03-18). "'Visual snow' – a disorder distinct from persistent migraine aura" (in en). Brain 137 (5): 1419–1428. doi:10.1093/brain/awu050. ISSN 1460-2156. PMID 24645145. 
  21. ↑ "Headache Classification Committee of the International Headache Society (IHS) The International Classification of Headache Disorders, 3rd edition" (in en). Cephalalgia 38 (1): 1–211. 2018-01-25. doi:10.1177/0333102417738202. ISSN 0333-1024. PMID 29368949. 
  22. ↑ Angueyra, J. M.; Rieke, F. (October 6, 2013). "Origin and effect of phototransduction noise in primate cone photoreceptors". Nature Neuroscience 16 (11): 1692–1700. doi:10.1038/nn.3534. PMID 24097042. 
  23. ↑ Mewes, R. (November 4, 2022). "Recent developments on psychological factors in medically unexplained symptoms and somatoform disorders". Frontiers in Public Health 10. doi:10.3389/fpubh.2022.1033203. PMID 36408051. 
  24. ↑ Sweeny, Timothy D.; Grabowecky, Marcia; Paller, Ken A.; Suzuki, Satoru (2008-05-01). "Random and systematic effects of neural noise on low-level and high-level pattern vision". Journal of Vision 8 (6): 593. doi:10.1167/8.6.593. ISSN 1534-7362. https://jov.arvojournals.org/article.aspx?articleid=2137308. 
  25. ↑ Li, Yanfeng; Luo, Yongbiao; Zheng, Yingjian; Liu, Guiqian; Gong, Jiekai (2024-10-21). "Research on Target Image Classification in Low-Light Night Vision". Entropy 26 (10): 882. doi:10.3390/e26100882. ISSN 1099-4300. PMID 39451958. Bibcode: 2024Entrp..26..882L. 
  26. ↑ Ala-Laurila, Petri (2025-01-21). "Visual pigments underlie the sensitivity difference between day and night vision". Proceedings of the National Academy of Sciences of the United States of America 122 (3). doi:10.1073/pnas.2424071122. ISSN 1091-6490. PMID 39805024. Bibcode: 2025PNAS..12224071A. 
  27. ↑ de Graaf, T. A.; Duecker, F.; Stankevich, Y.; Ten Oever, S.; Sack, A. T. (2017). "Seeing in the dark: Phosphene thresholds with eyes open versus closed in the absence of visual inputs". Brain Stimulation 10 (4): 828–835. doi:10.1016/j.brs.2017.04.127. ISSN 1876-4754. PMID 28522346. 
  28. ↑ Schwiedrzik, Caspar M. (2009). "Retina or visual cortex? The site of phosphene induction by transcranial alternating current stimulation". Frontiers in Integrative Neuroscience 3: 6. doi:10.3389/neuro.07.006.2009. ISSN 1662-5145. PMID 19506706. 
  29. ↑ 29.0 29.1 Raghavan, Manoj; Remler, Bernd F.; Rozman1, Stephanie; Pelli, Denis G. (2010). "Patients with visual 'snow' have normal equivalent input noise levels". Investigative Ophthalmology & Visual Science (51). https://psych.nyu.edu/pelli/pubs/raghavan2010arvo-snow.pdf. Retrieved 2017-04-12. 
  30. ↑ Dunn, FA; Rieke, F (August 2006). "The impact of photoreceptor noise on retinal gain controls". Current Opinion in Neurobiology 16 (4): 363–70. doi:10.1016/j.conb.2006.06.013. PMID 16837189. 
  31. ↑ Hass, C. A.; Angueyra, J. M.; Lindbloom-Brown, Z.; Rieke, F.; Horwitz, G. D. (November 2, 2015). "Chromatic detection from cone photoreceptors to V1 neurons to behavior in rhesus monkeys". Journal of Vision 15 (15): 1. doi:10.1167/15.15.1. PMID 26523737. 
  32. ↑ International Headache Society. The International Classification of Headache Disorders, 2nd edition" Cephalalgia 2004; 24 (suppl. 1): 1-160.
  33. ↑ "Headache". http://casemed.case.edu/clerkships/neurology/NeurLrngObjectives/Headache.htm. 
  34. ↑ Schankin, Christoph; Goadsby, Peter (2015). "Visual Snow—Persistent Positive Visual Phenomenon Distinct from Migraine Aura". Current Pain and Headache Reports Uncommon and/or Unusual Headaches and Syndromes (6): 23. doi:10.1007/s11916-015-0497-9. PMID 26021756. https://link.springer.com/content/pdf/10.1007/s11916-015-0497-9.pdf. 
  35. ↑ Puledda, Francesca; Goadsby, Peter (2021). "Localised increase in regional cerebral perfusion in patients with visual snow syndrome: a pseudo-continuous arterial spin labelling study". Migraine 92 (9): 918–926. doi:10.1136/jnnp-2020-325881. PMID 34261750. PMC 8372400. https://jnnp.bmj.com/content/jnnp/92/9/918.full.pdf. 
  36. ↑ MIchels, Lars; Traber, Ghislaine (21 September 2021). "Widespread White Matter Alterations in Patients With Visual Snow Syndrome". Frontiers in Neurology 12. doi:10.3389/fneur.2021.723805. PMID 34621237. 
  37. ↑ Puledda, F., Dipasquale, O., Gooddy, B. J., Karsan, N., Bose, R., Mehta, M. A., Williams, S., & Goadsby, P. (2023). Abnormal Glutamatergic and Serotonergic Connectivity in Visual Snow Syndrome and Migraine with Aura. Annals of Neurology, 94(5), 873–884. https://doi.org/10.1002/ana.26745
  38. ↑ Ala-Laurila, Petri; Rieke, Fred (December 2, 2014). "Coincidence Detection of Single-Photon Responses in the Inner Retina at the Sensitivity Limit of Vision". Current Biology 24 (24): 2888–2898. doi:10.1016/j.cub.2014.10.028. PMID 25454583. PMC 4269560. Bibcode: 2014CBio...24.2888A. https://www.researchgate.net/publication/268526375. 
  39. ↑ Silva, Elisa Martins; Puledda, Francesca (August 8, 2023). "Visual snow syndrome and migraine: a review" (in en). Eye 37 (12): 2374–2378. doi:10.1038/s41433-023-02435-w. ISSN 1476-5454. PMID 36788360. 
  40. ↑ Gomides, Dr. Mariuche; Starling-Alves, Isabela; H. Santos, Dr Flavia (2023-12-06). "Chapter 11 - Insights into pathophysiology and treatment of visual snow syndrome: A systematic review". Update on Emerging Treatments for Migraine. Progress on Brain Research. 255. Elsevier. pp. 311–326. doi:10.1016/bs.pbr.2020.05.020. ISBN 978-0-443-22310-5. https://www.sciencedirect.com/science/article/abs/pii/S0079612320300625. 
  41. ↑ Neurofeedback in Visual Snow. U.S. National Library of Medicine. August 2021. https://clinicaltrials.gov/ct2/show/NCT04902365. 
  42. ↑ Transcranial Magnetic Stimulation For Visual Snow Syndrome (TMSVS). U.S. National Library of Medicine. 7 June 2021. https://clinicaltrials.gov/ct2/show/NCT04925232. 
  43. ↑ Puledda, Francesca; Vandenbussche, Nicolas et al. (16 October 2021). "Evaluation of treatment response and symptom progression in 400 patients with visual snow syndrome". British Journal of Ophthalmology 106 (9): 1318–1324. doi:10.1136/bjophthalmol-2020-318653. PMID 34656983. 
Classification



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