Visual snow

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Visual snow is a transitory or persisting visual symptom where people see snow or television-like static in parts or the whole of their visual fields, constantly in all light conditions even visible in day-light. The severity or density of the "snow" differs from one person to the next; in some circumstances, it can inhibit a person's daily life, making it difficult to read, drive, perform routine tasks, see in detail (even in bright daylight) and focus correctly because of afterimages and other visual and non-visual symptoms.

Little is known about this rare condition, and it has conventionally been regarded as a variant of migraine aura (symptom)—though recent research shows this is not the case. Visual snow is now regarded as a unique syndrome—usually presenting with other symptoms, such as persistent afterimages, photophobia, enhanced blue field entoptic phenomenon and tinnitus.[1]

Newly published research has confirmed a “brain dysfunction in patients with visual snow”, located principally in the right lingual gyrus. Before this, no other etiology for visual snow had been identified. Insofar as sufferers of visual snow had undergone ophthalmic, neurological and psychiatric examinations, no systematic problems besides the visual snow were found. The recent research that indicates the disorder occurs in the brain has important ramifications for treatment possibilities however at the moment no treatment options have been established.

Causes[edit]

In May 2014 the results from the first major research trial into visual snow were reported.[2] The study described strong evidence from functional magnetic resonance imaging (fMRI) that the disease is caused by hypermetabolism in the right lingual gyrus and left cerebellar anterior lobe of the brain. The researchers stated that pinpointing visual snow (and its related symptoms such as afterimages) to a functional problem in a specific brain area may open up possibiities for targeted treatment and that treatment trials will follow.

Example of visual snow-like noise

Visual snow can occur in a variety of ophthalmic disorders that can be diagnosed by the presence of additional clinical signs and symptoms. Persisting visual snow can feature as a leading symptom of a migraine complication called persistent aura without infarction,[3] commonly referred to as persistent migraine aura (PMA). It is important to keep in mind that there exist many clinical sub-forms of migraine where headache may be absent and where the migraine aura may not take the typical form of the zigzagged fortification spectrum, but manifests with a large variety of focal neurological symptoms.

A condition that sometimes produces visual snow is optic neuritis (inflammation of the optic nerve), caused by multiple sclerosis (MS). Moreover, a variety of illnesses (e.g., Lyme disease, auto-immune disease) or noxious events (e.g. prolonged use of a VDU, dehydration, over-acidification) have been blamed by sufferers in self-help internet forums as causes of persisting visual snow, but none of these claims have been confirmed by scientific study. Some patients fail to find any apparent causative illness or event in their lives, instead saying the snow came out of nowhere or has been with them for their whole life.

The role of hallucinogens in the etiology of visual snow is not entirely obvious. Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, is sometimes linked to visual snow,[4] but both the connection of visual snow to HPPD [5] and the etiology and prevalence of HPPD is disputed.[6] Most of the evidence for both is generally anecdotal, and subject to spotlight fallacy.[7][8]

Related symptoms[edit]

In addition to visual snow, many sufferers have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others.[9]

Non-visual symptoms such as tinnitus, depersonalization-derealization, fatigue, speech difficulties and cognitive dysfunction (brain fog) are frequently encountered.[citation needed] Secondary psychiatric sequelae such as anxiety, panic attacks or depression may develop and necessitate appropriate treatment.[citation needed]

Treatments[edit]

There currently is no established treatment for visual snow.

In HPPD, clonazepam has been recommended as medication of first choice in patients seeking medical help.[10] Furthermore, drug abstinence is sometimes believed of major therapeutic importance in HPPD. In persistent aura without infarction, the evidence so far suggests that acetazolamide may be the premier drug for patients with the repetitive form of aura status[11] and that valproate,[12] lamotrigine,[13] or topiramate[14] should be first choices for patients with the continuous form. When these oral drugs are ineffective, an intravenous injection or injections of furosemide should be tried.[15] This said, visual snow appears to be neither definitively related to HPPD or migraines, and treatment of either might not translate well to visual snow.

For the time being the effectiveness of such treatments remains based solely on anecdotal evidence. Beyond pharmacological approaches, appropriate counseling and cognitive behavioral interventions that focus on coping with the condition may be of huge importance.

See also[edit]

References[edit]

  1. ^ Schankin, CJ, Maniyar, FH, Digre, KB, Goadsby, PJ, 2014, ‘Visual snow’ – a disorder distinct from persistent migraine aura, Brain doi: 10.1093/brain/awu050
  2. ^ 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
  3. ^ International Headache Society. The International Classification of Headache Disorders, 2nd edition. Cephalalgia 2004; 24 (suppl. 1): 1-160.
  4. ^ Abraham HD. Visual phenomenology of the LSD flashback. Arch Gen Psychiatry 1983; 40: 884-889.
  5. ^ 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–S36.006. doi:10.1212/WNL.78.1_MeetingAbstracts.S36.006. 
  6. ^ 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. 
  7. ^ 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–S36.006. doi:10.1212/WNL.78.1_MeetingAbstracts.S36.006. 
  8. ^ 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. 
  9. ^ Podoll K, Dahlem M, Greene S. Persistent migraine aura symptoms aka visual snow.
  10. ^ Lerner AG, Kladman I, Kodesh A, Sigal M, Shufman E. LSD-induced Hallucinogen Persisting Perception Disorder treated with clonazepam: two case reports. Isr J Psychiatry Relat Sci 2001; 38: 133-136.
  11. ^ Haan J, Sluis P, Sluis LH, Ferrari MD. Acetazolamide treatment for migraine aura status. Neurology 2000; 55: 1588-1589.
  12. ^ Rothrock JF. Successful treatment of persistent migraine aura with divalproex sodium. Neurology 1997; 48: 261-262.
  13. ^ Chen WT, Fuh JL, Lu SR, Wang SJ. Persistent migrainous visual phenomena might be responsive to lamotrigine. Headache 2001; 41: 823-825.
  14. ^ Podoll K, Dahlem M, Haas DC. Persistent migraine aura without infarction - a detailed description
  15. ^ Rozen TD. Treatment of a prolonged migrainous aura with intravenous furosemide. Neurology 2000; 55: 732-733.

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