Visual snow

Summary

Visual snow syndrome
Other namesPersistent positive visual phenomenon,[1] visual static, aeropsia
Red-blue-noise.gif
Animated example of visual snow-like noise
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 onsetEarly to middle adulthood[1]
CausesUnknown,[3] anxiety[citation needed], 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

Visual snow, also known as visual static, is an uncommon neurological condition in which the affected individuals see white or black dots or transparent dots in part or the whole of their visual fields.[7][4] The condition is typically always present and can last years.[10] Migraine and tinnitus are common comorbidities and are both associated with a more severe presentation of the syndrome.[11]

The cause of visual snow is unclear.[3] The underlying mechanism is believed to involve excessive excitability of neurons in the right lingual gyrus and left anterior lobe of cerebellum.[4][6] Research has been limited because of issues of case identification and diagnosis, the latter now largely addressed, and the limited size of any studied cohort. Initial functional brain imaging research suggests visual snow is a brain disorder.

There is no established treatment for visual snow. Medications that may be used to treat the condition include lamotrigine, acetazolamide, or verapamil.[4] However, these do not commonly result in benefits and the evidence for their use is very limited.[7][3]

Signs and symptoms

Clear vision versus disturbed vision

People report seeing "snow", much like the visual noise or "static" on a TV screen after transmission ends. In addition to this visual snow, many of those affected have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others.[12]

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 the visual symptoms.[11]

Diagnosis

Visual snow syndrome is usually diagnosed with the following proposed criteria:[13][14][11]

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

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]

Psychological side effects 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.[15] In a 2010 study, Raghaven et al. hypothesize that what the patients see as "snow" is eigengrau.[15] 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".[16]

Causes

The causes are unclear.[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,[17] 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.[18]

Visual snow does not depend on the effect of psychotropic substances on the brain.[11] Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, is sometimes linked to visual snow,[19] but both the connection of visual snow to HPPD[8] and the cause and prevalence of HPPD is disputed.[9] Most of the evidence for both is generally anecdotal, and subject to spotlight fallacy.[8][9]

Another mechanism is a thalamocortical dysrhythmia of the visual pathway similar to tinnitus which is a thalamocortical dysrhythmia of the auditory pathway.[citation needed]

Timeline

  • In September 2021, two studies[20] found white matter alterations in parts of the visual cortex and outside the visual cortex in patients with visual snow syndrome.
  • In June 2021, University of Colorado researchers started recruiting for a clinical trial on transcranial magnetic stimulation for visual snow syndrome.
  • In May 2021, University of Zurich researchers announced a clinical trial on neurofeedback for visual snow syndrome.
  • In December 2020, a study[21] found local increases in regional cerebral perfusion in patients with visual snow syndrome.
  • In May 2015, visual snow was described as a persisting positive visual phenomenon distinct from migraine aura in a study by Schankin and Goadsby.[22]

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] Medications that may be used include lamotrigine, acetazolamide, or verapamil,[4] but these do not always result in benefits.[7][3] As of 2021, there are two ongoing clinical trials using transcranial magnetic stimulation and neurofeedback for visual snow.[23][24]

References

  1. ^ a b Licht, Joseph; Ireland, Kathryn; Kay, Matthew. "Visual Snow: Clinical Correlations and Workup A Case Series". researchgate.net. Larkin Community Hospital. Retrieved 3 September 2017.
  2. ^ a b >https://www.visualsnowinitiative.org/diagnostic-criteria/
  3. ^ a b c d e f Brodsky, Michael C. (2016). Pediatric Neuro-Ophthalmology. Springer. p. 285. ISBN 9781493933846.
  4. ^ a b c d e f g 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. S2CID 4829787.
  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. S2CID 4829787.
  6. ^ a b c d 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. ^ a b c d e Dodick, David; Silberstein, Stephen D. (2016). Migraine. Oxford University Press. p. 53. ISBN 9780199793617.
  8. ^ a b c 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): S36.006. doi:10.1212/WNL.78.1_MeetingAbstracts.S36.006.
  9. ^ a b c 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. ^ 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. S2CID 6770765.
  11. ^ a b c d Puledda, Francesca; Schankin, Christoph; Goadsby, Peter (2020). "Visual snow syndrome. A clinical and phenotypical description of 1,100 cases" (PDF). Neurology. 94 (6): e564–e574. doi:10.1212/WNL.0000000000008909. PMC 7136068. PMID 31941797.
  12. ^ Podoll K, Dahlem M, Greene S. Persistent migraine aura symptoms aka visual snow. (archived Feb 8, 2012)
  13. ^ 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. 137 (5): 1419–1428. doi:10.1093/brain/awu050. ISSN 1460-2156. PMID 24645145.
  14. ^ "Headache Classification Committee of the International Headache Society (IHS) The International Classification of Headache Disorders, 3rd edition". Cephalalgia. 38 (1): 1–211. 2018-01-25. doi:10.1177/0333102417738202. ISSN 0333-1024. PMID 29368949.
  15. ^ a b Raghavan, Manoj; Remler, Bernd F.; Rozman1, Stephanie; Pelli, Denis G. (2010). "Patients with visual 'snow' have normal equivalent input noise levels" (PDF). Investigative Ophthalmology & Visual Science (51). Retrieved 2017-04-12.
  16. ^ 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. S2CID 15543432.
  17. ^ International Headache Society. The International Classification of Headache Disorders, 2nd edition" Cephalalgia 2004; 24 (suppl. 1): 1-160.
  18. ^ "Headache". casemed.case.edu. Retrieved 2019-11-04.
  19. ^ Abraham HD (1983). "Visual phenomenology of the LSD flashback". Arch Gen Psychiatry. 40 (8): 884–889. doi:10.1001/archpsyc.1983.01790070074009. PMID 6135405.
  20. ^ MIchels, Lars; Ghislaine, Traber (21 September 2021). "Widespread White Matter Alterations in Patients With Visual Snow Syndrome". Frontiers in Neurology. doi:10.3389/fneur.2021.723805.
  21. ^ Puledda, Francesca; Goadsby, Peter. "Localised increase in regional cerebral perfusion in patients with visual snow syndrome: a pseudo-continuous arterial spin labelling study" (PDF). Migraine. doi:10.1136/jnnp-2020-325881. PMC 8372400.
  22. ^ Schankin, Christoph; Goadsby, Peter. "Visual Snow—Persistent Positive Visual Phenomenon Distinct from Migraine Aura" (PDF). Uncommon and/or Unusual Headaches and Syndromes. doi:10.1007/s11916-015-0497-9. Cite journal requires |journal= (help)
  23. ^ "Neurofeedback in Visual Snow". ClinicalTrials.gov. U.S. National Library of Medicine.
  24. ^ "Transcranial Magnetic Stimulation For Visual Snow Syndrome (TMSVS)". ClinicalTrials.gov. U.S. National Library of Medicine.

External links

  • Visual Snow Initiative
  • Visual snow syndrome at NIH
  • http://visualsnowsyndrome.com/
  • Eye On Vision Foundation
Classification
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