Christoph J. Schankin, Farooq H. Maniyar, Kathleen B. Digre, Peter J. Goadsby
Brain, Volume 137, Issue 5, May 2014, Pages 1419–1428, https://doi.org/10.1093/brain/awu050
Published:18 March 2014

Abstract

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.

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M. Viana, F. Puledda, P. J. Goadsby
First published: 01 June 2020
 https://doi.org/10.1111/ene.14369

Abstract

Background and purpose

Visual snow manifests as a pan-field, dynamic visual disturbance described as continuous television static-like tiny flickering dots. Current diagnostic criteria further require at least two additional symptoms for visual snow syndrome (VSS) from: palinopsia (afterimages and trailing); entoptic phenomena (floaters, blue field entoptic phenomenon, photopsia, self-light of the eye); photophobia and nyctalopia. Our objective was to compare the phenotype of VSS in an Italian and British population.

Methods

Patients with VSS were characterized clinically using the current criteria. An online survey was prepared in collaboration with the patient group Eye-on-Vision. Patients were directed to the site if they contacted us by email asking to be involved in research. After data collection, we compared the phenotypic characteristics of a subgroup of British versus Italian patients taking part in the survey. As we expected more responses from the UK, we matched 100 UK patients for gender and age with our Italian cohort.

Results

Patients were enrolled from the UK (n = 100) and Italy (n = 100). The populations had similar demography. After multiple correction testing there were no differences in VSS features between the two groups. The same was true for the prevalence of migraine and previous use of recreational drugs.

Conclusion

This is the first study comparing the phenotype of VSS between two distinct populations. Our findings suggest that the visual snow phenotype, as well as migraine comorbidity, is similar across the two groups.

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Francesca Puledda, Dominic Ffytche, David J. Lythgoe, Owen O’Daly, Christoph Schankin, Steven C. R. Williams, Peter J. Goadsby
First published: 10 March 2020
 https://doi.org/10.1002/acn3.50986

Objective

To investigate the pathophysiology of visual snow (VS), through a combined functional neuroimaging and magnetic resonance spectroscopy (1H-MRS) approach.

Methods

We applied a functional MRI block-design protocol studying the responses to a visual stimulation mimicking VS, in combination with 1H-MRS over the right lingual gyrus, in 24 patients with VS compared to an equal number of age- and gender-matched healthy controls.

Results

We found reduced BOLD responses to the visual stimulus with respect to baseline in VS patients compared to controls, in the left (k = 291; P = 0.025; peak MNI coordinate [-34 12 -6]) and right (k = 100; P = 0.003; peak MNI coordinate [44 14 -2]) anterior insula. Our spectroscopy analysis revealed a significant increase in lactate concentrations in patients with respect to controls (0.66 ± 0.9 mmol/L vs. 0.07 ± 0.2 mmol/L; P < 0.001) in the right lingual gyrus. In this area, there was a significant negative correlation between lactate concentrations and BOLD responses to visual stimulation (P = 0.004; r = −0.42), which was dependent on belonging to the patient group.

Interpretation

As shown by our BOLD analysis, VS is characterized by a difference in bilateral insular responses to a visual stimulus mimicking VS itself, which could be due to disruptions within the salience network. Our results also suggest that patients with VS have a localized disturbance in extrastriate anaerobic metabolism, which may in turn cause a decreased metabolic reserve for the regular processing of visual stimuli.

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Christoph J. Schankin MD, Farooq H. Maniyar MD, Till Sprenger MD, Denise E. Chou MD, Michael Eller MD, Peter J. Goadsby MD, PhD
First published: 09 May 2014
https://doi.org/10.1111/head.12378

Objective

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.

Results
(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).

Conclusions

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.

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Ozan Eren, Christoph J Schankin
First Published May 20, 2020 Research Article
https://doi.org/10.1177/2514183X20925695

Results:Mirtazapine has no effect on VSS, neither positive nor negative. This is in line with the reports from the literature suggested only some beneficial effects from lamotrigine.

Conclusions:Since the pathophysiology of VSS is not fully understood, we still rely on the reports of individual cases or patient series. This includes not only the positive, but also the negative results to avoid unnecessary treatment trials. Looking into the literature, antidepressants do not seem to be a solution for the visual symptoms. So far, best data exists for the anticonvulsant lamotrigine.
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Ozan E Eren, Ruth Ruscheweyh, Andreas Straube, Christoph J Schankin
First Published December 22, 2019 Brief Report Find in PubMed
https://doi.org/10.1177/0333102419896780

Results

Patients with VSS had an increased L-VISS-score compared to matched controls [(22.2 ± 5.9 vs. 4.4 ± 4.8; ANOVA, factors VSS and comorbid migraine: Main effect for VSS (F = 100.70; p < 0.001), but not for migraine (F < 0.01; p = 1.00) or the interaction (F = 1.93; p = 0.16)]. An L-VISS-score of 14 identified VSS with a sensitivity and specificity of 95% (Receiver Operating Characteristic analysis, 0.986 ± 0.014, p ≤ 0.001).

Conclusion

Patients with VSS suffer continuously from photophobia at a level similar to chronic migraineurs during attacks. Although migraine and VSS share dysfunctional visual processing, patients with VSS might be more severely affected.

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Christoph J Schankin, Farooq H Maniyar, Denise E Chou, Michael Eller, Till Sprenger, Peter J Goadsby
Brain, Volume 143, Issue 4, April 2020, Pages 1106–1113, https://doi.org/10.1093/brain/awaa053
Published: 24 March 2020

AbstractPatients with visual snow syndrome suffer from a continuous pan-field visual disturbance, additional visual symptoms, tinnitus, and non-perceptional symptoms. The pathophysiology of visual symptoms might involve dysfunctional visual cortex. So far, the extra-visual system has not been investigated. We aimed at identifying structural and functional correlates for visual and non-visual symptoms in visual snow syndrome. Patients were compared to age- and sex-matched controls using 18F-2-fluoro-2-deoxy-D-glucose PET (n = 20 per group) and voxel-based morphometry (n = 17 per group). Guided by the PET results, region of interest analysis was done in voxel-based morphometry to identify structural-functional correspondence. Grey matter volume was assessed globally. Patients had corresponding hypermetabolism and cortical volume increase in the extrastriate visual cortex at the junction of the right lingual and fusiform gyrus. There was hypometabolism in the right superior temporal gyrus and the left inferior parietal lobule. Patients had grey matter volume increases in the temporal and limbic lobes and decrease in the superior temporal gyrus. The corresponding structural and functional alterations emphasize the relevance of the visual association cortex for visual snow syndrome. The broad structural and functional footprint, however, confirms the clinical impression that the disorder extends beyond the visual system.
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Authors: Puledda, Francesca; Schankin, Christoph; Digre, Kathleen; Goadsby, Peter J.; 
Source: Current Opinion in Neurology, Volume 31, Number 1, February 2018, pp. 52-58(7)
Publisher: Wolters Kluwer
DOI: https://doi.org/10.1097/WCO.0000000000000523

Purpose of review

We provide an overview of the neurological condition known as visual snow syndrome. Patients affected by this chronic disorder suffer with a pan-field visual disturbance described as tiny flickering dots, which resemble the static noise of an untuned television.

Recent findings

The term ‘visual snow’ has only appeared in the medical literature very recently. The clinical features of the syndrome have now been reasonably described and the pathophysiology has begun to be explored. This review focuses on what is currently known about visual snow.

​Summary

Recent evidence suggests visual snow is a complex neurological syndrome characterized by debilitating visual symptoms. It is becoming better understood as it is systematically studied. Perhaps the most important unmet need for the condition is a sufficient understanding of it to generate and test hypotheses about treatment.

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Francesca Puledda,  Christoph Schankin, Peter J. Goadsby
First published January 15, 2020, DOI: https://doi.org/10.1212/WNL.000000000000890

Results The visual snow population had an average age of 29 years and had no sex prevalence. The disorder usually started in early life, and ≈40% of patients had symptoms for as long as they could remember. The most commonly experienced static was black and white. Floaters, afterimages, and photophobia were the most reported additional visual symptoms. A latent class analysis showed that visual snow does not present with specific clinical endophenotypes. Severity can be classified by the amount of visual symptoms experienced. Migraine and tinnitus had a very high prevalence and were independently associated with a more severe presentation of the syndrome.

​Conclusions Clinical characteristics of visual snow did not differ from the previous cohort in the literature, supporting validity of the current criteria. Visual snow likely represents a clinical continuum, with different degrees of severity. On the severe end of the spectrum, it is more likely to present with its common comorbid conditions, migraine and tinnitus. Visual snow does not depend on the effect of psychotropic substances on the brain.
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