Wednesday, August 3, 2016

Visual snow

Inspired by a patient

Visual snow or visual static 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 daylight. The severity or density of the "snow" differs from one person to the next; in some circumstances, it can negatively affect a person's daily life, making it difficult to read, drive, perform routine tasks, see in detail (even in bright daylight) or 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—though recent research shows this is not the case. It is commonly confused with floaters by opticians and doctors alike when patients describe their symptoms, leading to misdiagnosis as well as underdiagnosis of visual snow. 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.

Research has confirmed a “brain dysfunction in patients with visual snow”, located principally in the right lingual gyrus.  Before this, no other cause 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 this disorder occurs in the brain has important ramifications for the possibility of potential treatment. However, standard treatment protocols have yet to be established.

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.

Non-visual symptoms such as ringing in the ears, depersonalization-derealization, feeling tired, speech difficulties and cognitive dysfunction (brain fog) are frequently encountered.[citation needed] Secondary psychiatric sequelae such as anxiety, panic attacks or depression may develop due to lack of answers and general ignorance of the condition in medical practice.

In May 2014 the results from the first major research trial into visual snow were reported. The study described strong evidence from positron emission tomography scans that the disease is associated with 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 possibilities for targeted treatment and that treatment trials will follow.

Visual snow can occur in a variety of ophthalmic conditions that can be diagnosed by the presence of additional clinical signs and experiences.

Persisting visual snow can feature as a leading addition to a migraine complication called persistent aura without infarction,  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). Moreover, a variety of illnesses (e.g., Lyme disease, auto-immune disease) or noxious events (dehydration) 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 lives.

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,  but both the connection of visual snow to HPPD[7] and the etiology and prevalence of HPPD is disputed.  Most of the evidence for both is generally anecdotal, and subject to spotlight fallacy.

Proposed diagnostic criteria for the "visual snow" syndrome:

Dynamic, continuous, tiny dots in the entire visual field.
At least one additional symptom:
Palinopsia (visual trailing and afterimages)
Enhanced entoptic phenomena (floaters, photopsia, blue field entoptic phenomenon, self-light of the eye)
Impaired night vision
Symptoms are not consistent with typical migraine aura.
Symptoms are not attributed to another disorder (ophthalmological, drug abuse).

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.
There is no established treatment for visual snow.

In HPPD, clonazepam has been recommended as medication of first choice in patients seeking medical help. 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  and that valproate, lamotrigine, or Topiramate 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.


  1. Schankin CJ, Maniyar FH, Sprenger T, Chou DE, Eller M, Goadsby PJ. The relation between migraine, typical migraine aura and "visual snow". Headache. 2014 Jun;54(6):957-66.

    To assess the relationship between the phenotype of the "visual snow" syndrome, comorbid migraine, and typical migraine aura on a clinical basis and using functional brain imaging.
    Patients with "visual snow" suffer from continuous TV-static-like tiny flickering dots in the entire visual field. Most patients describe a syndrome with additional visual symptoms of the following categories: palinopsia ("afterimages" and "trailing"), entopic phenomena arising from the optic apparatus itself (floaters, blue field entoptic phenomenon, photopsia, self-light of the eye), photophobia, nyctalopia (impaired night vision), as well as the non-visual symptom tinnitus. The high prevalence of migraine and typical migraine aura in this population has led to the assumption that "visual snow" is caused by persistent migraine aura. Due to the lack of objective measures, alternative diagnoses are malingering or a psychogenic disorder.
    (1) The prevalence of additional visual symptoms, tinnitus, and comorbid migraine as well as typical migraine aura was assessed in a prospective semi-structured telephone interview of patients with "visual snow." Correlations were calculated using standard statistics with P < .05 being considered statistically significant. (2) Areas with increased brain metabolism in a group of "visual snow" patients in comparison to healthy controls were identified using [(18) F]-2-fluoro-2-deoxy-D-glucose positron emission tomography and statistical parametric mapping (SPM8 with whole brain analysis; statistical significance was defined by P < .001 uncorrected for multiple comparisons).
    (1) Of 120 patients with "visual snow," 70 patients also had migraine and 37 had typical migraine aura. Having comorbid migraine was associated with an increased likelihood of having palinopsia (odds ratio [OR] 2.8; P = .04 for "afterimages" and OR 2.6; P = .01 for "trailing"), spontaneous photopsia (OR 2.9; P = .004), photophobia (OR 3.2; P = .005), nyctalopia (OR 2.7; P = .01), and tinnitus (OR 2.9; P = .006). Typical migraine aura was associated with an increased likelihood of spontaneous photopsia (OR 2.4; P = .04). (2) After adjusting for typical migraine aura, comparison of 17 "visual snow" patients with 17 age and gender matched controls showed brain hypermetabolism in the right lingual gyrus (Montreal Neurological Institute coordinates 16-78-5; kE  = 101; ZE  = 3.41; P < .001) and the left cerebellar anterior lobe adjacent to the left lingual gyrus (Montreal Neurological Institute coordinates -12-62-9; kE  = 152; ZE  = 3.28; P = .001).
    -Comorbid migraine aggravates the clinical phenotype of the "visual snow" syndrome by worsening some of the additional visual symptoms and tinnitus. This might bias studies on "visual snow" by migraineurs offering study participation more likely than non-migraineurs due to a more severe clinical presentation. The independence of entoptic phenomena from comorbid migraine indicates "visual snow" is the main determinant. The hypermetabolic lingual gyrus confirms a brain dysfunction in patients with "visual snow." The metabolic pattern differs from interictal migraine with some similarities to migrainous photophobia. The findings support the view that "visual snow," migraine, and typical migraine aura are distinct syndromes with shared pathophysiological mechanisms that need to be addressed in order to develop rational treatment strategies for this disabling condition.

  2. Rastogi RG, VanderPluym J, Lewis KS. Migrainous Aura, Visual Snow, and "Alice in Wonderland" Syndrome in Childhood. Semin Pediatr Neurol. 2016 Feb;23(1):14-7.

    Migraine is a condition that is common in the pediatric and adolescent population. Among children with migraine, visual aura can consist of either negative or positive features or both. Reports of sensory auras can also be elicited with a careful history. The understanding of the types of aura, as well as their relation to the more typical features of migraine, are discussed. The similar phenomena of visual snow and Alice in Wonderland syndrome in children are also described in detail.

  3. Schankin CJ, Goadsby PJ. Visual snow--persistent positive visual phenomenon distinct from migraine aura. Curr Pain Headache Rep. 2015 Jun;19(6):23.

    Patients with visual snow complain of uncountable flickering tiny dots in the entire visual field similar to the view of a badly tuned analogue TV channel (TV snow). The symptoms are often continuous and can persist over years. This condition is grouped among the persistent visual phenomena in migraine, although it clinically presents a unique entity distinct from persistent migraine aura or migraine aura status. Here, we review the recent literature leading to the identification of the visual snow syndrome. The additional visual and non-visual symptoms are described in detail, and criteria are presented for future studies. Using these criteria, the relationship to migraine and typical migraine aura was recently evaluated. Further, patients with visual snow differ from controls in respect of hypermetabolism in the supplementary visual cortex (lingual gyrus). This provides evidence that visual snow, despite being purely subjective in the individual patient, has a clear biological basis. The area of hypermetabolism overlaps with the functional correlates of photophobia in migraine supporting the close relationship of migraine and visual snow.

  4. Schankin CJ, Maniyar FH, Digre KB, Goadsby PJ. 'Visual snow' - a disorder distinct from persistent migraine aura. Brain. 2014 May;137(Pt 5):1419-28.

    Patients with 'visual snow' report continuous tiny dots in the entire visual field similar to the noise of an analogue television. As they frequently have migraine as a comorbidity with ophthalmological, neurological and radiological studies being normal, they are offered various diagnoses, including persistent migraine aura, post-hallucinogen flashback, or psychogenic disorder. Our aim was to study patients with 'visual snow' to characterize the phenotype. A three-step approach was followed: (i) a chart review of patients referred to us identified 22 patients with 'visual snow'. Fifteen had additional visual symptoms, and 20 patients had comorbid migraine, five with aura; (ii) to identify systematically additional visual symptoms, an internet survey (n = 275) of self-assessed 'visual snow' subjects done by Eye On Vision Foundation was analysed. In two random samples from 235 complete data sets, the same eight additional visual symptoms were present in >33% of patients: palinopsia (trailing and afterimages), entoptic phenomena (floaters, blue field entoptic phenomenon, spontaneous photopsia, self-light of the eye), photophobia, and nyctalopia (impaired night vision); and (iii) a prospective semi-structured telephone interview in a further 142 patients identified 78 (41 female) with confirmed 'visual snow' and normal ophthalmological exams. Of these, 72 had at least three of the additional visual symptoms from step (ii). One-quarter of patients had 'visual snow' as long as they could remember, whereas for the others the mean age of onset was 21 ± 9 years. Thirty-two patients had constant visual symptoms, whereas the remainder experienced either progressive or stepwise worsening. Headache was the most frequent symptom associated with the beginning or a worsening of the visual disturbance (36%), whereas migraine aura (seven patients) and consumption of illicit drugs (five, no hallucinogens) were rare. Migraine (59%), migraine with aura (27%), anxiety and depression were common comorbidities over time. Eight patients had first degree relatives with visual snow. Clinical investigations were not contributory. Only a few treatment trials have been successful in individual patients. Our data suggest that 'visual snow' is a unique visual disturbance clinically distinct from migraine aura that can be disabling for patients. Migraine is a common concomitant although standard migraine treatments are often unhelpful. 'Visual snow' should be considered a distinct disorder and systematic studies of its clinical features, biology and treatment responses need to be commenced to begin to understand what has been an almost completely ignored problem.

  5. Simpson JC, Goadsby PJ, Prabhakar P. Positive persistent visual symptoms (visual snow) presenting as a migraine variant in a 12-year-old girl. Pediatr Neurol. 2013 Nov;49(5):361-3.

    Migraine is a common neurological disorder affecting children, in which the headache is often preceded or accompanied by a complex of neurological symptoms known as an aura. Persistent visual symptoms are rare, with typical visual aura sometimes being poorly distinguished from other visual disturbances.
    We describe the case of a 12-year-old girl who has experienced persistent, constant symptoms throughout the visual fields of white, bright, jagged spots and black and white flashes with sparkles and dots since May 2010. She also has palinopsia, squiggles, and photophobia. The child's drawing of her visual symptoms helps illustrate the case and illuminate her ordeal.
    The child's visual symptoms have so far been resistant to pharmacological therapy.
    Further insight is needed into this debilitating condition to allow effective management in the pediatric population.

  6. the Medical Profession seriously needs to, how shall I put this, get its ‘arse into gear’ to find a way to help relieve the untold misery many sufferers endure daily.

  7. Thank you for taking the time to write this article there is little info on it