Visual snow

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In the Visual Snow Syndrome is a neurological disorder characterized by persistent noise in the entire visual field is marked. Those affected see many small dots that flicker rapidly, similar to the noise of an analog television. This description gave the name of the disease that goes beyond this circumscribed visual disorder. An association with migraines is often reported. Originally it was assumed that the visual snow syndrome is visual perception disorders in the context of the migraine aura . This is not the case, as current research shows. Rather, it is to be assumed that the disease is independent.

Epidemiology

The visual snow syndrome mainly begins in young adulthood. Some patients state that they have experienced the symptoms described since birth. A sudden onset of illness with no apparent cause is often reported. The previous intake of substances does not seem to be related to the occurrence of the clinical picture. Epidemiologically , the clinical picture has a lot in common with the clinical pictures migraine and HPPD . Exact data on the number of people affected are not available.

Clinical manifestations

Typically, clinical-neurological and ophthalmological findings show no abnormalities. In order to differentiate the clinical picture from persistent auras of a migraine, examinations were carried out with a precise clinical characterization, recording of concomitant diseases and disease courses in a larger group of patients. Based on this, the following diagnostic criteria were postulated.

Diagnostic criteria for visual snow syndrome according to ICHD-3
A. Visual snow: dynamic, continuously present small points in the entire binocular field of view, which last longer than 3 months
B. Presence of at least two other visual symptoms in the following four categories
I. Palinopsia (illusions of objects that were recently in the field of vision). At least one of the following: afterimages (different from retinal afterimages) or “trailing” (tracks) of moving objects
II Pronounced entoptic phenomena. At least one of the following: excessive floaters in both eyes (flying mosquitoes), " self-light " of the eye (colored clouds, whirlpools, waves), spontaneous photopsia (perception of lightning, sparks, asterisks), or excessive blue-field phenomenon (perception countless tiny, rapidly moving points when looking into bright blue light, such as the sky)
III Photophobia (sensitivity to light)
IV Nyctalopia (impaired twilight vision )
C. Symptoms are inconsistent with typical migraine visual aura
D. The symptoms cannot be better explained by other disorders

Concomitant diseases include in particular various forms of migraines. Other non-visual symptoms such as tinnitus , concentration disorders or secondary depersonalization are observed more frequently. In addition, there is an association with depression and anxiety , concomitant diseases that can also be increasingly diagnosed in chronic migraines.

root cause

The etiology (cause) of Visual Snow is so far unclear. There are various considerations with regard to the pathogenesis (origin).

Hypothesis of hyperexcitability

One possible explanation is an imbalance between inhibition and excitation of the visual cortex. A clue is the disturbed perception of both contrast and brightness in those affected, which in a certain respect coincides with a possible over-excitability of the primary visual cortex. The hypothesis is also supported by the results of imaging procedures ( PET ), which show a high glucose turnover and associated high activity in the right lingual gyrus and in the left anterior cerebellar lobe , two areas in the brain. However, there is currently only one case study in which the presumed over-excitability of the visual cortex could be directly demonstrated by means of electrophysiological measurements.

Role of the thalamus

Wearing tinted glasses is often associated with a subjective improvement in symptoms. The majority of patients in a clinical study found relief, especially with colored glasses that are transparent to short wavelengths of the visible light spectrum (blue). A comparable effect has already been shown for migraines and epilepsy, among others.

Color signals in the blue-yellow spectrum are transmitted by neurons of the coniocellular system. Since a symptomatic improvement could be demonstrated in the signal processing of such visual stimuli, a positive regulatory effect is assumed when the coniocellular system is activated. It is unclear whether the blocking of long-wave light (red) and the associated activation of the parvocellular system play a major role. Regardless of the deeper pathophysiological considerations, the hypothesis of a thalamocortical dysrhythmia is considered. Accordingly, a dysfunction of the connections in the brain that run from the thalamus to the visual cortex is suspected.

Neurotransmitters

The American neuroscientist James. T. Fulton speculates about a possible chemical imbalance of the neurotransmitters glutamate , GABA & dopamine .

"The symptoms of these people suffering visual snow provide pretty interesting evidence that visual snow, along with other psychedelic affects are due to changes in the local chemistry of the brain, probably due to changes in the levels of glutamic acid, GABA and dopamine-like pharmaceuticals. "

Investigation methods

The diagnosis of Visual Snow is made through a patient survey with a medical history ( anamnesis ) and ultimately constitutes a diagnosis of exclusion. Since the visual symptoms described can also be an expression of various organic brain diseases, a corresponding neurological diagnosis should be carried out to rule out these.

treatment

There is currently no standardized therapy. In isolated cases, anticonvulsants (e.g. lamotrigine) can be effective. It is also recommended to wear tinted glasses.

supporting documents

  1. ↑ Jäger HR, Giffin NJ, Goadsby PJ: Diffusion- and perfusion-weighted MR imaging in persistent migrainous visual disturbances. Cephalalgia. 2005 May; 25 (5): 323-332. PMID 15839846
  2. ↑ CJ Schankin, F. Maniyar, J. Hoffmann, D. Chou, PJ Goadsby: Clinical characterization of “visual snow” (Positive Persistent Visual Disturbance) . In: The Journal of Headache and Pain . tape 14 , no. 1 , February 21, 2013, ISSN  1129-2377 , p. P132 , doi : 10.1186 / 1129-2377-14-s1-p132 .
  3. ↑ Francesca Puledda, Christoph Schankin, Peter J. Goadsby: Visual snow syndrome: A clinical and phenotypical description of 1,100 cases . In: Neurology . January 15, 2020, ISSN  0028-3878 , p. 10.1212 / WNL.0000000000008909 , doi : 10.1212 / WNL.0000000000008909 ( neurology.org [accessed January 22, 2020]).
  4. ↑ Schankin, CJ, Maniyar, FH, Digre, KB, Goadsby, PJ (2014): 'Visual snow' - a disorder distinct from persistent migraine aura. In: Brain doi: 10.1093 / brain / awu050
  5. ^ Headache Classification Committee of the International Headache Society (IHS) The International Classification of Headache Disorders, 3rd edition . In: Cephalalgia . tape 38 , no. 1 , January 2018, ISSN  0333-1024 , p. 1-211 , doi : 10.1177 / 0333102417738202 ( sagepub.com [accessed December 2, 2018]).
  6. ^ U. Beyer, C. Gaul: "Visual snow" . In: The neurologist . tape 86 , no. 12 , December 1, 2015, ISSN  1433-0407 , p. 1561-1565 , doi : 10.1007 / s00115-015-4401-y .
  7. ↑ a b A. Bou Ghannam, VS Pelak: Visual Snow: a Potential Cortical Hyperexcitability Syndrome . In: Current Treatment Options in Neurology . 19, No. 9, March 27, 2017, ISSN  1534-3138 . doi : 10.1007 / s11940-017-0448-3 .
  8. ↑ Christoph J. Schankin, Farooq H. Maniyar, Till Sprenger, Denise E. Chou, Michael Eller, Peter J. Goadsby: The Relation Between Migraine, Typical Migraine Aura and "Visual Snow" . In: Headache: The Journal of Head and Face Pain . 54, No. 6, June 1, 2014, ISSN  1526-4610 , pp. 957-966. doi : 10.1111 / head.12378 .
  9. ^ Sebastian Luna, Daniel Lai, Alison Harris: Antagonistic Relationship Between VEP Potentiation and Gamma Power in Visual Snow Syndrome . In: Headache: The Journal of Head and Face Pain . tape 58 , no. 1 , January 2018, p. 138-144 , doi : 10.1111 / head.13231 ( wiley.com [accessed March 20, 2019]).
  10. ↑ a b Jenny L. Lauschke a, b, Gordon T. Plant c, Clare L. Fraser (2015): Visual snow: A thalamocortical dysrhythmia of the visual pathway? In: Journal of Clinical Neuroscience 28 (2016) 123–127 doi: 10.1016 / j.jocn.2015.12.001
  11. ↑ Visual Snow Initiative: Visual Snow Conference 2018: Dr. Victoria Pelak. July 3, 2018, accessed September 15, 2018 .
  12. ↑ James T. Fulton: Visual snow (snowy vision); a disease resulting from two different error mechanisms. Retrieved October 6, 2018 .
  13. ^ Robin M. van Dongen, Lindy C. Waaijer, Gerrit LJ Onderwater, Michel D. Ferrari, Gisela M. Terwindt: Treatment effects and comorbid diseases in 58 patients with visual snow . In: Neurology . tape 93 , no. 4 , 23 July 2019, ISSN  0028-3878 , p. e398 – e403 , doi : 10.1212 / WNL.0000000000007825 , PMID 31213497 , PMC 6669936 (free full text) - ( neurology.org [accessed January 22, 2020]).

See also