Visual snow syndrome explained

Visual snow syndrome
Synonyms:	Persistent positive visual phenomenon,^[1] visual static, aeropsia
Field:	Neurology, Neuro-ophthalmology
Symptoms:	Static and auras in vision, Palinopsia, Blue field entoptic phenomenon, Nyctalopia, Tinnitus
Complications:	Poor quality of vision, Photophobia, Heliophobia, Depersonalization and Derealization^[2]
Onset:	Visual Snow can appear at any time, but it commonly appears at birth, late teenage years, and early adulthood.
Causes:	Unknown,^[3] hyperexcitability of neurons and processing problems in the visual cortex^[4]
Risks:	Migraine sufferer, psychoactive substance use
Differential:	Migraine aura, Persistent aura without infarction, Hallucinogen persisting perception disorder
Medication:	Anticonvulsants (limited evidence and success)
Frequency:	Uncommon (understudied)

Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or colored dots across the whole visual field.^{[5] [6]}

Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches.^{[7] [8]} The condition is typically always present and has no known cure, as viable treatments are still under research.^[9] 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.^[10] Temporomandibular joint dysfunction (TMJ) may also be a common comorbidity.

The cause of the syndrome is unclear.^[11] 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. 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.^[12]

Signs and symptoms

In addition to visual snow, many of those affected have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others.^[13]

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.

Non-visual symptoms may include difficulty concentrating, insomnia, frequent migraines, nausea, and vertigo. ^[14]

Diagnosis

Visual snow syndrome is usually diagnosed with the following proposed criteria:^{[15] [16]}

• 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:
  • i. Palinopsia. At least 1 of the following: afterimages or trailing of moving objects.
  • ii. Enhanced entoptic phenomena. At least 1 of the following: excessive floaters in both eyes, excessive blue field entoptic phenomenon, self-light of the eye (phosphenes), or spontaneous photopsia.
  • iii. Photophobia.
  • iv. Nyctalopia; impaired night vision.
• Symptoms are not consistent with typical migraine aura.
• Symptoms are not better explained by another disorder (ophthalmological, drug abuse).
  • Normal ophthalmology tests (best-corrected visual acuity, dilated fundus examination, visual field, and electroretinogram); not caused by previous intake of psychotropic drugs.

Additional and non-visual symptoms like tinnitus, ear pressure, brain fog, and more might be present. It can also be diagnosed by PET scan.

Common misconceptions

• 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 known as the Ganzfeld Effect. In conditions of low illumination, especially in dimly lit environments, this phenomenon is related to how the eyes and the brain process visual information in insufficient lighting. The visual system becomes more sensitive to light and can amplify noise or minor changes in visual signals. It's important to note that the perception of such phenomena may vary among different individuals due to individual differences in perception and sensitivity.
• When the eyes are closed, visual static may be related to the first level of visual hallucination.
• 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.^{[17] [18]}

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.

Psychological side effects of visual snow can include depersonalization, derealization, depression, photophobia, and heliophobia in the individual affected.

Patients with visual "snow" have normal equivalent input noise levels and contrast sensitivity. In a 2010 study, Raghaven et al. hypothesize that what the patients see as "snow" is eigengrau.^[19] 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".^{[20] [21]}

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,^[6] specifically the right lingual gyrus and left cerebellar anterior lobe of the brain.^[22]

Persisting visual snow can feature as a leading addition to a migraine complication called persistent aura without infarction,^[23] 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.^[24]

Visual snow does not depend on the effect of psychotropic substances on the brain.^[10] Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, is sometimes linked to visual snow,^[25] but both the connection of visual snow to HPPD^[26] and the cause and prevalence of HPPD are disputed.^[27] Most of the evidence for both is generally anecdotal and subject to spotlight fallacy.^{[26] [27]} Visual snow has also been correlated with head trauma and infection.^[28]

Timeline

• In May 2015, visual snow was described as a persisting positive visual phenomenon distinct from migraine aura in a study by Schankin and Goadsby.^[29]
• In December 2020, a study^[30] found local increases in regional cerebral perfusion in patients with visual snow syndrome.
• In September 2021, two studies^[31] 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^[32] 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.^[33]

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.^[6] 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.^[34] Medications that may be used include lamotrigine, acetazolamide, verapamil,^[6] clonazepam, propranolol, and sertraline^[35] but these do not always result in positive effects.^[3] As of 2021, two ongoing clinical trials were using transcranial magnetic stimulation and neurofeedback for visual snow.^{[36] [37]}

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.^[38]

Notes and References

1. Joseph. Licht. Kathryn. Ireland. Matthew. Kay. Visual Snow: Clinical Correlations and Workup A Case Series. researchgate.net. 2016 . Larkin Community Hospital. 3 September 2017. 10.13140/RG.2.1.2393.9443.
2. Web site: Diagnostic Criteria | Visual Snow Initiative. 23 March 2023 .
3. Book: Brodsky. Michael C.. Pediatric Neuro-Ophthalmology. 2016. Springer. 9781493933846. 285. en.
4. Visual Snow: A Potential Cortical Hyperexcitability Syndrome. 28349350. 2017. Bou Ghannam. A.. Pelak. V. S.. Current Treatment Options in Neurology. 19. 3. 9. 10.1007/s11940-017-0448-3. 4829787.
5. Book: Dodick. David. Silberstein. Stephen D.. Migraine. 2016. Oxford University Press. 9780199793617. 53. en.
6. Bou Ghannam. A. Pelak. VS. Visual snow: a potential cortical hyperexcitability syndrome. Current Treatment Options in Neurology. March 2017. 19. 3. 9. 10.1007/s11940-017-0448-3. 28349350. 4829787.
7. Web site: Visual snow syndrome - About the Disease - Genetic and Rare Diseases Information Center . 2022-10-30 . rarediseases.info.nih.gov . en.
8. Puledda . Francesca . Schankin . Christoph . Goadsby . Peter J. . 2020-02-11 . Visual snow syndrome: A clinical and phenotypical description of 1,100 cases . Neurology . en . 94 . 6 . e564–e574 . 10.1212/WNL.0000000000008909 . 0028-3878 . 31941797. 7136068 .
9. Schankin. CJ. Goadsby. PJ. Visual snow--persistent positive visual phenomenon distinct from migraine aura. Current Pain and Headache Reports. June 2015. 19. 6. 23. 10.1007/s11916-015-0497-9. 26021756. 6770765.
10. Puledda . Francesca . Schankin . Christoph . Goadsby . Peter . Visual snow syndrome. A clinical and phenotypical description of 1,100 cases. . Neurology . 2020 . 94 . 6 . e564–e574 . 10.1212/WNL.0000000000008909 . 31941797 . 7136068 .
11. Book: Brodsky. Michael C.. Pediatric Neuro-Ophthalmology. 2016. Springer. 9781493933846. 285. en.
12. Piccirelli. Marco. Michels. Lars. February 2, 2020 . Visual snow syndrome: a review on diagnosis, pathophysiology, and treatment . Current Opinion in Neurology . en . 33 . 1 . 74–78 . 10.1097/WCO.0000000000000768 . 1350-7540 . NHI. Traber. Ghislaine L.. 31714263.
13. Podoll K, Dahlem M, Greene S. Persistent migraine aura symptoms aka visual snow. (archived Feb 8, 2012)
14. Cleveland Clinic. (2024). Visual Snow Syndrome. https://my.clevelandclinic.org/health/diseases/24444-visual-snow-syndrome.
15. Schankin. Christoph J.. Maniyar. Farooq H.. Digre. Kathleen B.. Goadsby. Peter J.. 2014-03-18. 'Visual snow' – a disorder distinct from persistent migraine aura. Brain. en. 137. 5. 1419–1428. 10.1093/brain/awu050. 24645145. 1460-2156. free.
16. 2018-01-25. Headache Classification Committee of the International Headache Society (IHS) The International Classification of Headache Disorders, 3rd edition. Cephalalgia. en. 2018-01-25. 38. 1. 1–211. 10.1177/0333102417738202. 29368949. 0333-1024. free.
17. October 6, 2013 . Origin and effect of phototransduction noise in primate cone photoreceptors. Nature Neuroscience. 3815624 . Angueyra . J. M. . Rieke . F. . 16 . 11 . 1692–1700 . 10.1038/nn.3534 . 24097042 .
18. November 4, 2022 . Recent developments on psychological factors in medically unexplained symptoms and somatoform disorders . Frontiers in Public Health. 9672811 . Mewes . R. . 10 . 10.3389/fpubh.2022.1033203 . free . 36408051 .
19. Manoj. Raghavan. Bernd F.. Remler. Stephanie. Rozman1. Denis G.. Pelli. Patients with visual 'snow' have normal equivalent input noise levels. 2010. Investigative Ophthalmology & Visual Science. 51. 2017-04-12. 2016-04-11. https://web.archive.org/web/20160411083446/http://psych.nyu.edu/pelli/pubs/raghavan2010arvo-snow.pdf. dead.
20. Dunn. FA. Rieke. F. The impact of photoreceptor noise on retinal gain controls. Current Opinion in Neurobiology. August 2006. 16. 4. 363–70. 10.1016/j.conb.2006.06.013. 16837189. 15543432.
21. November 2, 2015 . Chromatic detection from cone photoreceptors to V1 neurons to behavior in rhesus monkeys . Journal of Vision. 4633035 . Hass . C. A. . Angueyra . J. M. . Lindbloom-Brown . Z. . Rieke . F. . Horwitz . G. D. . 15 . 15 . 1 . 10.1167/15.15.1 . 26523737 .
22. Schankin, CJ, Maniyar, FH, Sprenger, T, Chou, DE, Eller, M, Goadsby, PJ, 2014, The Relation Between Migraine, Typical Migraine Aura and "Visual Snow", Headache,
23. International Headache Society. The International Classification of Headache Disorders, 2nd edition" Cephalalgia 2004; 24 (suppl. 1): 1-160.
24. Web site: Headache. casemed.case.edu. 2019-11-04. 2020-02-26. https://web.archive.org/web/20200226013125/http://casemed.case.edu/clerkships/neurology/NeurLrngObjectives/Headache.htm. dead.
25. Abraham HD . 1983 . Visual phenomenology of the LSD flashback . Arch Gen Psychiatry . 40 . 8. 884–889 . 10.1001/archpsyc.1983.01790070074009. 6135405 .
26. Schankin. C.. Maniyar. F.. Hoffmann. J.. Chou. D.. Goadsby. P.. Visual Snow: A New Disease Entity Distinct from Migraine Aura (S36.006). Neurology. 22 April 2012. 78. Meeting Abstracts 1. S36.006. 10.1212/WNL.78.1_MeetingAbstracts.S36.006.
27. Halpern. J. Hallucinogen persisting perception disorder: what do we know after 50 years?. Drug and Alcohol Dependence. 1 March 2003. 69. 2. 109–119. 10.1016/S0376-8716(02)00306-X. 12609692.
28. Leishangthem. Lakshmi. Yan. Yan. November 10, 2021 . Not All Cases of Visual Snows are Benign: Mimics of Visual Snow Syndrome . Neuropsychiatric Disease and Treatment . en . 17 . 3293–3300 . 10.2147/NDT.S338111. free. 1178-2021 . 8591117 . 34785899. Hang. Chenyue.
29. Schankin . Christoph . Goadsby . Peter . Visual Snow—Persistent Positive Visual Phenomenon Distinct from Migraine Aura . Current Pain and Headache Reports . 2015 . Uncommon and/or Unusual Headaches and Syndromes . 6 . 23 . 10.1007/s11916-015-0497-9 . 26021756 . 6770765 .
30. Puledda . Francesca . Goadsby . Peter . Localised increase in regional cerebral perfusion in patients with visual snow syndrome: a pseudo-continuous arterial spin labelling study . Migraine . 2021 . 92 . 9 . 918–926 . 10.1136/jnnp-2020-325881 . 34261750 . 8372400 .
31. MIchels . Lars . Traber . Ghislaine . Widespread White Matter Alterations in Patients With Visual Snow Syndrome . Frontiers in Neurology . 21 September 2021 . 12 . 723805 . 10.3389/fneur.2021.723805. 34621237 . 8490630 . free .
32. 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
33. December 2, 2014 . Coincidence Detection of Single-Photon Responses in the Inner Retina at the Sensitivity Limit of Vision . Current Biology. 2014CBio...24.2888A . Ala-Laurila . Petri . Rieke . Fred . 24 . 24 . 2888–2898 . 10.1016/j.cub.2014.10.028 . 25454583 . 4269560 .
34. Puledda. Francesca. August 8, 2023 . Visual snow syndrome and migraine: a review . Eye . en . 37 . 12 . 2374–2378 . 10.1038/s41433-023-02435-w . 1476-5454. 10397188 . Silva. Elisa Martins. 36788360.
35. Book: Gomides . Dr. Mariuche . https://www.sciencedirect.com/science/article/abs/pii/S0079612320300625 . Update on Emerging Treatments for Migraine . Starling-Alves . Isabela . H. Santos . Dr Flavia . Chapter 11 - Insights into pathophysiology and treatment of visual snow syndrome: A systematic review . Progress on Brain Research . 255 . 311–326 . Elsevier . 10.1016/bs.pbr.2020.05.020 . 33008511 . 978-0443223105 . 222146213 . 2023-12-06.
36. Neurofeedback in Visual Snow . ClinicalTrials.gov . August 2021 . U.S. National Library of Medicine.
37. Transcranial Magnetic Stimulation For Visual Snow Syndrome (TMSVS) . ClinicalTrials.gov . 7 June 2021 . U.S. National Library of Medicine.
38. Puledda . Francesca . Vandenbussche . Nicolas . Moreno-Ajona . David . Eren . Ozan . Schankin . Christoph . Goadsby . Peter J . 2 . Evaluation of treatment response and symptom progression in 400 patients with visual snow syndrome . British Journal of Ophthalmology . 16 October 2021 . 106 . 9 . 1318–1324 . 10.1136/bjophthalmol-2020-318653 . 34656983 . 9411880 . 239006203 . 3 February 2022.