Visual snow
From Wikipedia, the free encyclopedia
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, especially against dark backgrounds. There are different causes for visual snow, i.e. visual snow is non-specific. Therefore, each subject with a leading complaint of visual snow needs a full diagnostic work-up including ophthalmic, neurological and psychiatric examinations as well as an MRI scan of the brain.
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[edit] Causes
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 [1], 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.
Another possible cause of visual snow is hallucinogen persisting perception disorder (HPPD) following use of LSD, MDMA, psilocybin or other hallucinogens. In HPPD, the symptom of visual snow has been described [2] as aeropsia (literally "seeing the air"). It is noteworthy that HPPD can occur after a single dose of a hallucinogen and with a considerable latency between last drug intake and onset of persistent perception disorder, so taking a thorough life-time drug history is mandatory in the diagnostic work-up of visual snow.
Another 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 nocious 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 supported by evidence-based medicine. 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.
[edit] Related symptoms
In addition to visual snow, patients suffering from persistent perception disorder frequently have other types of visual disturbances such as starbursts, increased afterimages, floaters, trails, and many others [3]. Non-visual symptoms such as tinnitus or depersonalisation-derealisation are also frequently encountered. Secondary psychiatric sequelae such as anxiety, panic attacks or depression may develop and necessitate appropriate treatment.
[edit] Treatments
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 [4]. Furthermore, drug abstinence is sometimes said to be 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 [5] and that valproate [6], lamotrigine [7], or topiramate [8] 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 [9]. However, with very little scientific research on the condition taking place, for the time being the effectiveness of such treatments remains based solely on anecdotal evidence. Beyond pharmacological approaches, appropriate counselling and cognitive behavioral interventions that focus on coping with the condition may be of huge importance.
[edit] See also
[edit] References
- ^ International Headache Society. The International Classification of Headache Disorders, 2nd edition. Cephalalgia 2004; 24 (suppl. 1): 1-160.
- ^ Abraham HD. Visual phenomenology of the LSD flashback. Arch Gen Psychiatry 1983; 40: 884-889.
- ^ Podoll K, Dahlem M, Greene S. Persistent migraine aura symptoms aka visual snow.
- ^ 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.
- ^ Haan J, Sluis P, Sluis LH, Ferrari MD. Acetazolamide treatment for migraine aura status. Neurology 2000; 55: 1588-1589.
- ^ Rothrock JF. Successful treatment of persistent migraine aura with divalproex sodium. Neurology 1997; 48: 261-262.
- ^ Chen WT, Fuh JL, Lu SR, Wang SJ. Persistent migrainous visual phenomena might be responsive to lamotrigine. Headache 2001; 41: 823-825.
- ^ Podoll K, Dahlem M, Haas DC. Persistent migraine aura without infarction - a detailed description
- ^ Rozen TD. Treatment of a prolonged migrainous aura with intravenous furosemide. Neurology 2000; 55: 732-733.
[edit] External links
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