Visual snow syndrome

Last updated
Visual snow syndrome
Other namesPersistent positive visual phenomenon, [1] visual static, aeropsia
Red-blue-noise.gif
Animated example of visual snow-like noise
Specialty Neurology, Neuro-ophthalmology
Symptoms Static and auras in vision, Palinopsia, Blue field entoptic phenomenon, Nyctalopia, Tinnitus
Complications Poor quality of vision, Photophobia, Heliophobia, Depersonalization and Derealization [2]
Usual onsetVisual Snow can appear at any time, but it commonly appears at birth, late teenage years, and early adulthood.
CausesUnknown, [3] hyperexcitability of neurons and processing problems in the visual cortex [4] [5]
Risk factors Migraine sufferer, [6] psychoactive substance use
Differential diagnosis Migraine aura, [7] Persistent aura without infarction, Hallucinogen persisting perception disorder [8] [9]
Medication Anticonvulsants [7] [3] (limited evidence and success)
FrequencyUncommon (understudied)

Visual snow syndrome (VSS) is an uncommon neurological condition in which the primary symptom is that affected individuals see persistent flickering white, black, transparent, or colored dots across the whole visual field. [7] [4]

Contents

Other common symptoms are palinopsia, enhanced entoptic phenomena, photophobia, and tension headaches. [10] [11] The condition is typically always present and has no known cure, as viable treatments are still under research. [12] Astigmatism, although not presumed connected to these visual disturbances, is a common comorbidity. Migraines and tinnitus are common comorbidities that are both associated with a more severe presentation of the syndrome. [13] Temporomandibular joint dysfunction (TMJ) may also be a common comorbidity.[ citation needed ]

The cause of the syndrome is unclear. [3] The underlying mechanism is believed to involve excessive excitability of neurons in the right lingual gyrus and left anterior lobe of the cerebellum. Another hypothesis proposes that visual snow syndrome could be a type of thalamocortical dysrhythmia and may involve the thalamic reticular nucleus (TRN). A failure of inhibitory action from the TRN to the thalamus may be the underlying cause for the inability to suppress excitatory sensory information. [4] [6] Research has been limited due to issues of case identification, diagnosis, and the limited size of any studied cohort, though the issue of diagnosis is now largely addressed. Initial functional brain imaging research suggests visual snow is a brain disorder. [14]

Signs and symptoms

Normal vision vis-a-vis disturbed vision Vs with descriptions.jpg
Normal vision vis-à-vis disturbed vision

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. [15]

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 visual symptoms. [13]

Diagnosis

Visual snow syndrome is usually diagnosed with the following proposed criteria: [16] [17] [13]

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

Common misconceptions

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. [20] In a 2010 study, Raghaven et al. hypothesize that what the patients see as "snow" is eigengrau. [20] 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". [21] [22]

Causes

The causes of VSS are not clear. [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, [23] 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. [24]

Visual snow does not depend on the effect of psychotropic substances on the brain. [13] Hallucinogen persisting perception disorder (HPPD), a condition caused by hallucinogenic drug use, is sometimes linked to visual snow, [25] but both the connection of visual snow to HPPD [8] and the cause and prevalence of HPPD are disputed. [9] Most of the evidence for both is generally anecdotal and subject to spotlight fallacy. [8] [9] Visual snow has also been correlated with head trauma and infection. [26] [27]

Timeline

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] In some studies, lamotrigine as a treatment for visual snow syndrome only showed efficacy in 20% of patients, and in one study, patients using lamotrigine even reported worsening symptoms. [33] Medications that may be used include lamotrigine, acetazolamide, verapamil, [4] clonazepam, propranolol, and sertraline [34] but these do not always result in positive effects. [7] [3] As of 2021, two ongoing clinical trials were using transcranial magnetic stimulation and neurofeedback for visual snow. [35] [36]

A recent study in the British Journal of Ophthalmology has confirmed that common drug treatments are generally ineffective in visual snow syndrome (VSS). Vitamins and benzodiazepines, however, were shown to be beneficial in some patients and can be considered safe for this condition. [37]

Related Research Articles

<span class="mw-page-title-main">Migraine</span> Disorder resulting in recurrent moderate-severe headaches

Migraine is a genetically influenced complex neurological disorder characterized by episodes of moderate-to-severe headache, most often unilateral and generally associated with nausea and light and sound sensitivity. Other characterizing symptoms may include vomiting, cognitive dysfunction, allodynia, and dizziness. Exacerbation of headache symptoms during physical activity is another distinguishing feature. Up to one-third of migraine sufferers experience aura, a premonitory period of sensory disturbance widely accepted to be caused by cortical spreading depression at the onset of a migraine attack. Although primarily considered to be a headache disorder, migraine is highly heterogenous in its clinical presentation and is better thought of as a spectrum disease rather than a distinct clinical entity. Disease burden can range from episodic discrete attacks, consisting of as little as several lifetime attacks, to chronic disease.

<span class="mw-page-title-main">Headache</span> Pain in the head, neck, or face

Headache, also known as cephalalgia, is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches.

<span class="mw-page-title-main">Micropsia</span> Medical condition

Micropsia is a condition affecting human visual perception in which objects are perceived to be smaller than they actually are. Micropsia can be caused by optical factors, by distortion of images in the eye, by changes in the brain, and from psychological factors. Dissociative phenomena are linked with micropsia, which may be the result of brain-lateralization disturbance.

<span class="mw-page-title-main">Alice in Wonderland syndrome</span> Neurological disorder that distorts perception of objects size and distance

Alice in Wonderland syndrome (AIWS), also known as Todd's syndrome or dysmetropsia, is a neurological disorder that distorts perception. People with this syndrome may experience distortions in their visual perception of objects, such as appearing smaller (micropsia) or larger (macropsia), or appearing to be closer (pelopsia) or farther (teleopsia) than they are. Distortion may also occur for senses other than vision.

<span class="mw-page-title-main">Cluster headache</span> Neurological disorder

Cluster headache is a neurological disorder characterized by recurrent severe headaches on one side of the head, typically around the eye(s). There is often accompanying eye watering, nasal congestion, or swelling around the eye on the affected side. These symptoms typically last 15 minutes to 3 hours. Attacks often occur in clusters which typically last for weeks or months and occasionally more than a year.

Mal de debarquement syndrome is a neurological condition usually occurring after a cruise, aircraft flight, or other sustained motion event. The phrase mal de débarquement is French and translates to "illness of disembarkment".

Exploding head syndrome (EHS) is an abnormal sensory perception during sleep in which a person experiences auditory hallucinations that are loud and of short duration when falling asleep or waking up. The noise may be frightening, typically occurs only occasionally, and is not a serious health concern. People may also experience a flash of light. Pain is typically absent.

Hyperacusis is an increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly, but it is often categorized into four subtypes: loudness, pain, annoyance, and fear. It can be a highly debilitating hearing disorder.

<span class="mw-page-title-main">Hallucinogen persisting perception disorder</span> Medical condition

Hallucinogen persisting perception disorder (HPPD) is a non-psychotic disorder in which a person experiences apparent lasting or persistent visual hallucinations or perceptual distortions after using drugs, including but not limited to psychedelics, dissociatives, entactogens, tetrahydrocannabinol (THC), and SSRIs. Despite being designated as a hallucinogen-specific disorder, the specific contributory role of psychedelic drugs is unknown.

Palinopsia is the persistent recurrence of a visual image after the stimulus has been removed. Palinopsia is not a diagnosis; it is a diverse group of pathological visual symptoms with a wide variety of causes. Visual perseveration is synonymous with palinopsia.

<span class="mw-page-title-main">Aura (symptom)</span> Symptom of epilepsy and migraine

An aura is a perceptual disturbance experienced by some with epilepsy or migraine. An epileptic aura is actually a minor seizure.

Acephalgic migraine is a neurological syndrome. It is a relatively uncommon variant of migraine in which the patient may experience some migraine symptoms such as aura, nausea, photophobia, and hemiparesis, but does not experience headache. It is generally classified as an event fulfilling the conditions of migraine with aura with no headache. It is sometimes distinguished from visual-only migraine aura without headache, also called ocular migraine.

Persistent aura without infarction (PAWOI) is a rare and seemingly benign condition, first described in case reports in 1982 as "prolonged/persistent migraine aura status", and in 2000 as "migraine aura status", that is not yet fully understood. PAWOI is said to possibly be a factor involved in a variety of neurological symptoms, including visual snow, loss of vision, increased afterimages, tinnitus, and others. The pathogenesis of PAWOI is unknown. It is not clear which medical examinations are useful in diagnosing PAWOI. At present, PAWOI is usually diagnosed solely based on the patient's current and past symptoms. It is possible that an "overactive brain" or a chemical imbalance underlies the disorder. Various medications have been tried as treatment, notably acetazolamide, valproate, lamotrigine, topiramate, and furosemide.

New daily persistent headache (NDPH) is a primary headache syndrome which can mimic chronic migraine and chronic tension-type headache. The headache is daily and unremitting from very soon after onset, usually in a person who does not have a history of a primary headache disorder. The pain can be intermittent, but lasts more than 3 months. Headache onset is abrupt and people often remember the date, circumstance and, occasionally, the time of headache onset. One retrospective study stated that over 80% of patients could state the exact date their headache began.

Vestibular migraine (VM) is vertigo with migraine, either as a symptom of migraine or as a related neurological disorder.

The classification of all headaches, including migraines, is organized by the International Headache Society, and published in the International Classification of Headache Disorders (ICHD). The current version, the ICHD-3 beta, was published in 2013.

Migralepsy is a rare condition in which a migraine is followed, within an hour period, by an epileptic seizure. Because of the similarities in signs, symptoms, and treatments of both conditions, such as the neurological basis, the psychological issues, and the autonomic distress that is created from them, they individually increase the likelihood of causing the other. However, also because of the sameness, they are often misdiagnosed for each other, as migralepsy rarely occurs.

<span class="mw-page-title-main">Illusory palinopsia</span> Subtype of palinopsia

Illusory palinopsia is a subtype of palinopsia, a visual disturbance defined as the persistence or recurrence of a visual image after the stimulus has been removed. Palinopsia is a broad term describing a heterogeneous group of symptoms, which is divided into hallucinatory palinopsia and illusory palinopsia. Illusory palinopsia is likely due to sustained awareness of a stimulus and is similar to a visual illusion: the distorted perception of a real external stimulus.

A migrainous infarction is a rare type of ischaemic stroke which occurs in correspondence with migraine aura symptoms. Symptoms include headaches, visual disturbances, strange sensations and dysphasia, all of which gradually worsen causing neurological changes which ultimately increase the risk of an ischaemic stroke. Typically, women under the age of 45 who experience migraine with aura (MA) are at the greatest risk for developing migrainous infarction, especially when combined with smoking and use of oral contraceptives.

Menstrual migraine is the term used to describe both true menstrual migraines and menstrually related migraines. About 7%–14% of women have migraines only at the time of menstruation. These are called true menstrual migraines. Most female migraineurs experience migraine attacks throughout the menstruation cycle with an increased number perimenstrually, these are referred to as menstrually related or menstrually triggered migraine.

References

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  2. 1 2 "Diagnostic Criteria | Visual Snow Initiative". 23 March 2023.
  3. 1 2 3 4 5 Brodsky, Michael C. (2016). Pediatric Neuro-Ophthalmology. Springer. p. 285. ISBN   9781493933846.
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  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. 1 2 3 4 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
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  20. 1 2 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). Archived from the original (PDF) on 2016-04-11. Retrieved 2017-04-12.{{cite journal}}: CS1 maint: numeric names: authors list (link)
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  35. ↑ "Neurofeedback in Visual Snow". ClinicalTrials.gov. U.S. National Library of Medicine. August 2021.
  36. ↑ "Transcranial Magnetic Stimulation For Visual Snow Syndrome (TMSVS)". ClinicalTrials.gov. U.S. National Library of Medicine. 7 June 2021.
  37. ↑ Puledda, Francesca; Vandenbussche, Nicolas; et al. (16 October 2021). "Evaluation of treatment response and symptom progression in 400 patients with visual snow syndrome". British Journal of Ophthalmology. 106 (9): 1318–1324. doi:10.1136/bjophthalmol-2020-318653. PMC   9411880 . PMID   34656983. S2CID   239006203 . Retrieved 3 February 2022.
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