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Aeschlimann SA, Klein A, Schankin CJ. Visual snow syndrome: recent advances in understanding the pathophysiology and potential treatment approaches. Curr Opin Neurol 2024; 37:283-288. [PMID: 38465699 PMCID: PMC11064904 DOI: 10.1097/wco.0000000000001258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2024]
Abstract
PURPOSE OF REVIEW Visual snow syndrome (VSS) is a disorder characterized by persistent visual disturbances, including the visual snow phenomenon, palinopsia, heightened perception of entoptic phenomena, impaired night vision, and photophobia. The purpose of this review is to provide an update on recent findings over the past 18 months in VSS research and to summarize the current state of treatment approaches. RECENT FINDINGS Electrophysiological studies have revealed cortical hyperresponsivity in visual brain areas, imaging studies demonstrated microstructural and functional connectivity alterations in multiple cortical and thalamic regions and investigated glutamatergic and serotoninergic neurotransmission. These findings suggest that VSS might be a network disorder.Only few treatment studies are currently available demonstrating limited response to medication and even worsening or triggering of visual symptoms by certain antidepressants. Promising nonpharmacological treatments include mindfulness-based cognitive therapy, the use of chromatic filters, and research on visual noise adaption and neuro-optometric visual rehabilitation therapy (NORT). However, the level of evidence is still low and further research is needed including larger trials and involving objective measures of individual dysfunction. SUMMARY Although there has been recent progress, we still have not fully understood the nature of VSS. Further research is needed on a clinical and pathophysiological level to successfully treat the condition.
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Affiliation(s)
- Sarah A Aeschlimann
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Klein A, Aeschlimann SA, Zubler F, Scutelnic A, Riederer F, Ertl M, Schankin CJ. Alterations of the alpha rhythm in visual snow syndrome: a case-control study. J Headache Pain 2024; 25:53. [PMID: 38584260 PMCID: PMC11000394 DOI: 10.1186/s10194-024-01754-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 03/19/2024] [Indexed: 04/09/2024] Open
Abstract
BACKGROUND Visual snow syndrome is a disorder characterized by the combination of typical perceptual disturbances. The clinical picture suggests an impairment of visual filtering mechanisms and might involve primary and secondary visual brain areas, as well as higher-order attentional networks. On the level of cortical oscillations, the alpha rhythm is a prominent EEG pattern that is involved in the prioritisation of visual information. It can be regarded as a correlate of inhibitory modulation within the visual network. METHODS Twenty-one patients with visual snow syndrome were compared to 21 controls matched for age, sex, and migraine. We analysed the resting-state alpha rhythm by identifying the individual alpha peak frequency using a Fast Fourier Transform and then calculating the power spectral density around the individual alpha peak (+/- 1 Hz). We anticipated a reduced power spectral density in the alpha band over the primary visual cortex in participants with visual snow syndrome. RESULTS There were no significant differences in the power spectral density in the alpha band over the occipital electrodes (O1 and O2), leading to the rejection of our primary hypothesis. However, the power spectral density in the alpha band was significantly reduced over temporal and parietal electrodes. There was also a trend towards increased individual alpha peak frequency in the subgroup of participants without comorbid migraine. CONCLUSIONS Our main finding was a decreased power spectral density in the alpha band over parietal and temporal brain regions corresponding to areas of the secondary visual cortex. These findings complement previous functional and structural imaging data at a electrophysiological level. They underscore the involvement of higher-order visual brain areas, and potentially reflect a disturbance in inhibitory top-down modulation. The alpha rhythm alterations might represent a novel target for specific neuromodulation. TRIAL REGISTRATION we preregistered the study before preprocessing and data analysis on the platform osf.org (DOI: https://doi.org/10.17605/OSF.IO/XPQHF , date of registration: November 19th 2022).
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Affiliation(s)
- Antonia Klein
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland
| | - Sarah A Aeschlimann
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland
| | - Frederic Zubler
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland
| | - Adrian Scutelnic
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland
| | - Franz Riederer
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland
| | - Matthias Ertl
- Department of Psychology, University of Bern, Bern, CH 3010, Switzerland
- Neurocenter, Luzerner Kantonsspital, Lucerne, 6000, Switzerland
| | - Christoph J Schankin
- Department of Neurology Inselspital, Bern University Hospital, University of Bern, Rosenbühlgasse 25, Bern, CH-3010, Switzerland.
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Wong SH, Pontillo G, Kanber B, Prados F, Wingrove J, Yiannakas M, Davagnanam I, Gandini Wheeler-Kingshott CAM, Toosy AT. Visual Snow Syndrome Improves With Modulation of Resting-State Functional MRI Connectivity After Mindfulness-Based Cognitive Therapy: An Open-Label Feasibility Study. J Neuroophthalmol 2024; 44:112-118. [PMID: 37967050 PMCID: PMC10855987 DOI: 10.1097/wno.0000000000002013] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
BACKGROUND Visual snow syndrome (VSS) is associated with functional connectivity (FC) dysregulation of visual networks (VNs). We hypothesized that mindfulness-based cognitive therapy, customized for visual symptoms (MBCT-vision), can treat VSS and modulate dysfunctional VNs. METHODS An open-label feasibility study for an 8-week MBCT-vision treatment program was conducted. Primary (symptom severity; impact on daily life) and secondary (WHO-5; CORE-10) outcomes at Week 9 and Week 20 were compared with baseline. Secondary MRI outcomes in a subcohort compared resting-state functional and diffusion MRI between baseline and Week 20. RESULTS Twenty-one participants (14 male participants, median 30 years, range 22-56 years) recruited from January 2020 to October 2021. Two (9.5%) dropped out. Self-rated symptom severity (0-10) improved: baseline (median [interquartile range (IQR)] 7 [6-8]) vs Week 9 (5.5 [3-7], P = 0.015) and Week 20 (4 [3-6], P < 0.001), respectively. Self-rated impact of symptoms on daily life (0-10) improved: baseline (6 [5-8]) vs Week 9 (4 [2-5], P = 0.003) and Week 20 (2 [1-3], P < 0.001), respectively. WHO-5 Wellbeing (0-100) improved: baseline (median [IQR] 52 [36-56]) vs Week 9 (median 64 [47-80], P = 0.001) and Week 20 (68 [48-76], P < 0.001), respectively. CORE-10 Distress (0-40) improved: baseline (15 [12-20]) vs Week 9 (12.5 [11-16.5], P = 0.003) and Week 20 (11 [10-14], P = 0.003), respectively. Within-subject fMRI analysis found reductions between baseline and Week 20, within VN-related FC in the i) left lateral occipital cortex (size = 82 mL, familywise error [FWE]-corrected P value = 0.006) and ii) left cerebellar lobules VIIb/VIII (size = 65 mL, FWE-corrected P value = 0.02), and increases within VN-related FC in the precuneus/posterior cingulate cortex (size = 69 mL, cluster-level FWE-corrected P value = 0.02). CONCLUSIONS MBCT-vision was a feasible treatment for VSS, improved symptoms and modulated FC of VNs. This study also showed proof-of-concept for intensive mindfulness interventions in the treatment of neurological conditions.
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Stern JI, Robertson CE. Visual Snow: Updates and Narrative Review. Curr Pain Headache Rep 2024; 28:55-63. [PMID: 38079073 DOI: 10.1007/s11916-023-01186-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/25/2023] [Indexed: 02/22/2024]
Abstract
PURPOSE OF REVIEW Visual snow (VS) involves visualization of innumerable dots throughout the visual field, sometimes resembling "TV static." Patients who experience this symptom may also have additional visual symptoms (e.g., photophobia, palinopsia, floaters, and nyctalopia) with a pattern now defined as visual snow syndrome (VSS). This manuscript describes both VS and VSS in detail and provides an updated review on the clinical features, pathophysiology, and optimal management strategies for these symptoms. RECENT FINDINGS VS/VSS may be primary or secondary to a variety of etiologies, including ophthalmologic or brain disorders, systemic disease, and medication/hallucinogen exposure. Evaluation involves ruling out secondary causes and mimics of VS. Increasing evidence suggests that VSS is a widespread process extending beyond the visual system. Pathophysiology may involve cortical hyperexcitability or dysfunctional connectivity of thalamocortical or attention/salience networks. VSS is typically a benign, non-progressive syndrome and can be managed with non-medicine strategies. Though no medication provides complete relief, some may provide partial improvement in severity of VS.
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Affiliation(s)
- Jennifer I Stern
- Neurology Department, Mayo Clinic College of Medicine and Science, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, USA
| | - Carrie E Robertson
- Neurology Department, Mayo Clinic College of Medicine and Science, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, USA.
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Satgunam P, Kannan K, Hathibelagal AR. Understanding visual snow syndrome: A retrospective study from a tertiary eye care center. Indian J Ophthalmol 2024; 72:211-216. [PMID: 38099384 PMCID: PMC10941942 DOI: 10.4103/ijo.ijo_2180_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 05/02/2023] [Accepted: 05/16/2023] [Indexed: 12/19/2023] Open
Abstract
PURPOSE Visual snow syndrome is a debilitating neurological condition. A comprehensive eye examination may not detect any abnormalities in this condition. Presently the condition is recognized only through the history elicited. Hence, it becomes important to understand the presenting complaints and profile of these patients. A retrospective study at a tertiary eye care center was undertaken to achieve this goal. METHODS Electronic medical records of patients presenting to a Binocular Vision and Orthoptics clinic were reviewed. Records of the patients containing keywords such as "light sensitivity, shadowing, visual snow, multiple images, and night vision" were retrieved and inspected. Those matching the diagnostic criteria of visual snow syndrome were included in the study. RESULTS A total of 33 patients (average age ± standard deviation: 29.7 ± 9.8 years) were identified. Majority of the patients were males (69%). All the patients had logMAR visual acuity 0 or better in each eye. The most prominent (84.4%) presenting symptom was palinopsia (or afterimage or trailing). About 34.4% complained of floaters (including snow-like appearance). More than half (54.6%) of the patients also had binocular dysfunction. CONCLUSION Visual snow syndrome is a relatively new condition on the rise, with unclear pathology. The symptoms of this condition can easily be confused with regular floaters or black spots seen in vitreous and retinal pathologies. In the absence of such pathology, an elaborate history should be elicited, and the distress of the patient should be acknowledged. The patient should also be reassured that this is not a blinding condition.
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Affiliation(s)
- PremNandhini Satgunam
- Brien Holden Institute of Optometry and Vision Sciences, Hyderabad Eye Research Foundation, Hyderabad, Telangana, India
| | - Kiruthika Kannan
- Srimati Kanuri Santhamma Centre for Vitreoretinal Diseases, Anant Bajaj Retina Institute, L. V. Prasad Eye Institute, Hyderabad, Telangana, India
| | - Amithavikram R Hathibelagal
- Brien Holden Institute of Optometry and Vision Sciences, Hyderabad Eye Research Foundation, Hyderabad, Telangana, India
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Puledda F, Dipasquale O, Gooddy BJM, Karsan N, Bose R, Mehta MA, Williams SCR, Goadsby PJ. Abnormal Glutamatergic and Serotonergic Connectivity in Visual Snow Syndrome and Migraine with Aura. Ann Neurol 2023; 94:873-884. [PMID: 37466404 DOI: 10.1002/ana.26745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 06/22/2023] [Accepted: 07/15/2023] [Indexed: 07/20/2023]
Abstract
OBJECTIVE Neuropharmacological changes in visual snow syndrome (VSS) are poorly understood. We aimed to use receptor target maps combined with resting functional magnetic resonance imaging (fMRI) data to identify which neurotransmitters might modulate brain circuits involved in VSS. METHODS We used Receptor-Enriched Analysis of Functional Connectivity by Targets (REACT) to estimate and compare the molecular-enriched functional networks related to 5 neurotransmitter systems of patients with VSS (n = 24), healthy controls (HCs; n = 24), and migraine patients ([MIG], n = 25, 15 of whom had migraine with aura [MwA]). For REACT we used receptor density templates for the transporters of noradrenaline, dopamine, and serotonin, GABA-A and NMDA receptors, as well as 5HT1B and 5HT2A receptors, and estimated the subject-specific voxel-wise maps of functional connectivity (FC). We then performed voxel-wise comparisons of these maps among HCs, MIG, and VSS. RESULTS Patients with VSS had reduced FC in glutamatergic networks localized in the anterior cingulate cortex (ACC) compared to HCs and patients with migraine, and reduced FC in serotoninergic networks localized in the insula, temporal pole, and orbitofrontal cortex compared to controls, similar to patients with migraine with aura. Patients with VSS also showed reduced FC in 5HT2A -enriched networks, largely localized in occipito-temporo-parietal association cortices. As revealed by subgroup analyses, these changes were independent of, and analogous to, those found in patients with migraine with aura. INTERPRETATION Our results show that glutamate and serotonin are involved in brain connectivity alterations in areas of the visual, salience, and limbic systems in VSS. Importantly, altered serotonergic connectivity is independent of migraine in VSS, and simultaneously comparable to that of migraine with aura, highlighting a shared biology between the disorders. ANN NEUROL 2023;94:873-884.
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Affiliation(s)
- Francesca Puledda
- Headache Group, Wolfson SPaRRC, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- National Institute for Health Research (NIHR) King's Clinical Research Facility, King's College London, London, UK
| | - Ottavia Dipasquale
- National Institute for Health Research (NIHR) King's Clinical Research Facility, King's College London, London, UK
| | - Benjamin J M Gooddy
- Department of Neuroimaging, Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Nazia Karsan
- Headache Group, Wolfson SPaRRC, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- National Institute for Health Research (NIHR) King's Clinical Research Facility, King's College London, London, UK
| | - Ray Bose
- Headache Group, Wolfson SPaRRC, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- National Institute for Health Research (NIHR) King's Clinical Research Facility, King's College London, London, UK
| | - Mitul A Mehta
- Department of Neuroimaging, Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Steven C R Williams
- Department of Neuroimaging, Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Peter J Goadsby
- Headache Group, Wolfson SPaRRC, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- National Institute for Health Research (NIHR) King's Clinical Research Facility, King's College London, London, UK
- Department of Neurology, University of California, Los Angeles, Los Angeles, CA
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Silva EM, Puledda F. Visual snow syndrome and migraine: a review. Eye (Lond) 2023; 37:2374-2378. [PMID: 36788360 PMCID: PMC10397188 DOI: 10.1038/s41433-023-02435-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 01/19/2023] [Accepted: 01/30/2023] [Indexed: 02/16/2023] Open
Abstract
Visual snow syndrome is a neurological condition characterized by ongoing prominent phenomena described consistently as tiny dots moving across the entire visual field, often associated with complex visual symptoms. These can take the form of afterimages, entoptic phenomena, nyctalopia and light sensitivity. Although some of these symptoms can be benign, they can nonetheless become significantly impactful for many who experience them, particularly in cases that have a sudden and abrupt start. As visual snow syndrome becomes increasingly recognized in clinical practice we begin to learn about its typical presentation and underlying pathophysiology. Treatment of visual snow, however, still proves quite challenging, and efforts need to be focused on unravelling the biological mechanisms of the syndrome. This endeavour has characterized the most recent research on visual snow, mostly involving neuroimaging, neurophysiological and neurobehavioral studies aimed at understanding its underlying neural signature. Another important aspect of the syndrome, which will likely prove critical in deepening our understanding of visual snow, is represented by the intricate biological and historical connexion with migraine. This narrative review focused on visual snow syndrome will explore its clinical, pathophysiological and treatment aspects in detail.
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Affiliation(s)
| | - Francesca Puledda
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, UK.
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Rusztyn P, Stańska W, Torbus A, Maciejewicz P. Visual Snow: A Review on Pathophysiology and Treatment. J Clin Med 2023; 12:3868. [PMID: 37373563 DOI: 10.3390/jcm12123868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 05/28/2023] [Accepted: 06/02/2023] [Indexed: 06/29/2023] Open
Abstract
OBJECTIVE Visual snow (VS) is a rare clinical entity in neuro-ophthalmology. It is described as the presence of flickering dots affecting the whole visual field, often compared by patients to snow or pixelated television static. Importantly, it can be an alarming symptom for many patients, lowering their quality of life. Our purpose is to increase awareness of this disease, because many healthcare professionals have difficulty identifying symptoms as the nature of the condition is subjective. In this review, we aimed to describe the updates in the etiology and treatment of visual snow. We searched for articles in English, presenting original data and published after December 2019. Different studies show inconsistent data. Neuroimaging studies found, among other things, hypermetabolism of the lingual gyrus, increased gray matter in different brain areas, and altered connectivity in visual pathways. However, these findings were not present in all patients. According to the literature, among the most effective drugs is lamotrigine. Unfortunately, it also carries a risk of worsening the symptoms. It is crucial to remember that VS can be worsened or induced by alcohol, recreational drugs, and certain medication. In terms of treatment, nonpharmacological approaches such as color filters and repetitive Transcranial Magnetic Stimulation were also used. INTERPRETATION Further studies are needed to understand the nature of VS fully. Even though the pathophysiology and effective treatment of the condition remains unknown, expanding the knowledge about visual snow can impact the comfort of patients.
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Affiliation(s)
- Przemysław Rusztyn
- Students' Scientific Club, Department of Ophthalmology, Medical University of Warsaw, 02-005 Warsaw, Poland
| | - Wiktoria Stańska
- Students' Scientific Club, Department of Ophthalmology, Medical University of Warsaw, 02-005 Warsaw, Poland
| | - Anna Torbus
- Students' Scientific Club, Department of Ophthalmology, Medical University of Warsaw, 02-005 Warsaw, Poland
| | - Piotr Maciejewicz
- Department of Ophthalmology, Medical University of Warsaw, 02-005 Warsaw, Poland
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Frattale I, Papetti L, Ursitti F, Sforza G, Monte G, Voci A, Proietti Checchi M, Mazzone L, Valeriani M. Visual Disturbances Spectrum in Pediatric Migraine. J Clin Med 2023; 12:jcm12082780. [PMID: 37109116 PMCID: PMC10143789 DOI: 10.3390/jcm12082780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2023] [Revised: 04/04/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
Migraine is a complex neurological disorder with partially unknown pathophysiological mechanisms. The prevalence in childhood ranges from 7.7% to 17.8%, thus representing the most frequent primary headache. In half of the cases, migraine is accompanied or preceded by various neurological disturbances, among which the visual aura is the best known. In literature, other conditions, such as Alice in Wonderland Syndrome and Visual Snow syndrome, are characterized by visual manifestations and are often associated with migraine. The aim of this narrative review is to describe the spectrum of visual disturbances in pediatric migraine and their pathophysiological mechanisms.
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Affiliation(s)
- Ilaria Frattale
- Child Neurology and Psychiatry Unit, Systems Medicine Department, Hospital of Rome, Tor Vergata University, 00165 Rome, Italy
| | - Laura Papetti
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
| | - Fabiana Ursitti
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
| | - Giorgia Sforza
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
| | - Gabriele Monte
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
| | - Alessandra Voci
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
| | | | - Luigi Mazzone
- Child Neurology and Psychiatry Unit, Systems Medicine Department, Hospital of Rome, Tor Vergata University, 00165 Rome, Italy
| | - Massimiliano Valeriani
- Developmental Neurology, Bambino Gesù Children Hospital, IRCCS, 00165 Rome, Italy
- Center for Sensory Motor Interaction, Aalborg University, 9220 Aalborg, Denmark
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Solly EJ, Clough M, McKendrick AM, White OB, Fielding J. Eye movement characteristics are not significantly influenced by psychiatric comorbidities in people with visual snow syndrome. Brain Res 2023; 1804:148265. [PMID: 36709021 DOI: 10.1016/j.brainres.2023.148265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 01/11/2023] [Accepted: 01/23/2023] [Indexed: 01/26/2023]
Abstract
Visual snow syndrome (VSS) is a neurological disorder primarily affecting the processing of visual information. Using ocular motor (OM) tasks, we previously demonstrated that participants with VSS exhibit altered saccade profiles consistent with visual attention impairments. We subsequently proposed that OM assessments may provide an objective measure of dysfunction in these individuals. However, VSS participants also frequently report significant psychiatric symptoms. Given that that these symptoms have been shown previously to influence performance on OM tasks, the objective of this study was to investigate whether psychiatric symptoms (specifically: depression, anxiety, fatigue, sleep difficulties, and depersonalization) influence the OM metrics found to differ in VSS. Sixty-one VSS participants completed a battery of four OM tasks and a series of online questionnaires assessing psychiatric symptomology. We revealed no significant relationship between psychiatric symptoms and OM metrics on any of the tasks, demonstrating that in participants with VSS, differences in OM behaviour are a feature of the disorder. This supports the utility of OM assessment in characterising deficit in VSS, whether supporting a diagnosis or monitoring future treatment efficacy.
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Affiliation(s)
- Emma J Solly
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Meaghan Clough
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Allison M McKendrick
- Department of Optometry & Vision Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Owen B White
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Joanne Fielding
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia.
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Shu Y, Huang Y, Chen J, Chen L, Cai G, Guo Y, Li S, Gao J, Zeng X. Effects of primary angle-closure glaucoma on interhemispheric functional connectivity. Front Neurosci 2023; 17:1053114. [PMID: 36845423 PMCID: PMC9947534 DOI: 10.3389/fnins.2023.1053114] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 01/10/2023] [Indexed: 02/11/2023] Open
Abstract
Background Previous studies on primary angle-closure glaucoma (PACG) primarily focused on local brain regions or global abnormal brain activity; however, the alteration of interhemispheric functional homotopy and its possible cause of brain-wide functional connectivity abnormalities have not been well-studied. Little is known about whether brain functional alteration could be used to differentiate from healthy controls (HCs) and its correlation with neurocognitive impairment. Methods Forty patients with PACG and 40 age- and sex-matched healthy controls were recruited for this study; resting-state functional magnetic resonance imaging (rs-fMRI), and clinical data were collected. We used the voxel-mirrored homotopic connectivity (VMHC) method to explore between-group differences and selected brain regions with statistically significant differences as regions of interest for whole-brain functional connectivity analysis. Partial correlation was used to evaluate the association between abnormal VMHC values in significantly different regions and clinical parameters, with with age and sex as covariates. Finally, the support vector machine (SVM) model was performed in classification prediction of PACG. Results Compared with healthy controls, patients with PACG exhibited significantly decreased VMHC values in the lingual gyrus, insula, cuneus, and pre- and post-central gyri; no regions exhibited increased VMHC values. Subsequent functional connectivity analysis revealed extensive functional changes in functional networks, particularly the default mode, salience, visual, and sensorimotor networks. The SVM model showed good performance in classification prediction of PACG, with an area under curve (AUC) of 0.85. Conclusion Altered functional homotopy of the visual cortex, sensorimotor network, and insula may lead to impairment of visual function in PACG, suggesting that patients with PACG may have visual information interaction and integration dysfunction.
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Affiliation(s)
- Yongqiang Shu
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Yuying Huang
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Jingting Chen
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Liting Chen
- Medical Imaging Center, The First Affiliated Hospital of Jinan University, Guangzhou, China
| | - Guoqian Cai
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Yu Guo
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Shenghong Li
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Junwei Gao
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Xianjun Zeng
- Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, China,*Correspondence: Xianjun Zeng, ; orcid.org/0000-0003-4089-1568
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Differential Diagnosis of Visual Phenomena Associated with Migraine: Spotlight on Aura and Visual Snow Syndrome. Diagnostics (Basel) 2023; 13:diagnostics13020252. [PMID: 36673062 PMCID: PMC9857878 DOI: 10.3390/diagnostics13020252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 12/30/2022] [Accepted: 12/30/2022] [Indexed: 01/11/2023] Open
Abstract
Migraine is a severe and common primary headache disorder, characterized by pain as well as a plethora of non-painful symptoms. Among these, visual phenomena have long been known to be associated with migraine, to the point where they can constitute a hallmark of the disease itself. In this review we focus on two key visual disorders that are directly or indirectly connected to migraine: visual aura and visual snow syndrome (VSS). Visual aura is characterized by the transient presence of positive and negative visual symptoms, before, during or outside of a migraine attack. VSS is a novel stand-alone phenomenon which has been shown to be comorbid with migraine. We discuss key clinical features of the two disorders, including pathophysiological mechanisms, their differential diagnoses and best treatment practices. Our aim is to provide an aid for clinicians and researchers in recognizing these common visual phenomena, which can even appear simultaneously in patients with an underlying migraine biology.
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Scutelnic A, Slavova N, Klein A, Horvath T, de Beukelaer SAL, Arnold M, Jung S, Schankin CJ. Symptomatic visual snow in acute ischemic stroke: A case series. Headache 2023; 63:173-176. [PMID: 36651600 DOI: 10.1111/head.14445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 11/23/2022] [Accepted: 11/25/2022] [Indexed: 01/19/2023]
Abstract
Visual snow is the main symptom of visual snow syndrome, a disorder of predominantly visual disturbances initially described in patients without abnormalities on ancillary investigations. We present a case series of patients with visual snow in the setting of acute ischemic stroke. The first and second patient reported previous episodic visual snow with migraine attacks. The third patient experienced visual snow for the first time during the ischemic stroke. In the first patient, the ischemic stroke affected the right and left precuneus and the right lingual gyrus. In the second patient, the ischemic stroke was located in the left lingual gyrus, parts of the left fusiform and parahippocampal gyrus, left dorso-lateral thalamus, and left cerebellar hemisphere. In the third patient, occipital pole, trunk of the corpus callosum on the right, right paramedian pons, right cerebellar hemisphere, and vermis were affected. Our case series indicates that the symptom visual snow can be caused by vascular lesions in areas of visual processing. Because patients did not meet criteria for visual snow syndrome, dysfunction in the affected areas might only explain part of the complex pathophysiology of visual snow syndrome.
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Affiliation(s)
- Adrian Scutelnic
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Nedelina Slavova
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.,Institute of Diagnostic and Interventional Neuroradiology, Bern University Hospital, Bern, Switzerland
| | - Antonia Klein
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Thomas Horvath
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Sophie A L de Beukelaer
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Marcel Arnold
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Simon Jung
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Christoph J Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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14
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Strik M, Clough M, Solly EJ, Glarin R, White OB, Kolbe SC, Fielding J. Brain network dynamics in people with visual snow syndrome. Hum Brain Mapp 2022; 44:1868-1875. [PMID: 36478470 PMCID: PMC9980880 DOI: 10.1002/hbm.26176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 11/10/2022] [Accepted: 11/29/2022] [Indexed: 12/13/2022] Open
Abstract
Visual snow syndrome (VSS) is a neurological disorder characterized by a range of continuous visual disturbances. Little is known about the functional pathological mechanisms underlying VSS and their effect on brain network topology, studied using high-resolution resting-state (RS) 7 T MRI. Forty VSS patients and 60 healthy controls underwent RS MRI. Functional connectivity matrices were calculated, and global efficiency (network integration), modularity (network segregation), local efficiency (LE, connectedness neighbors) and eigenvector centrality (significance node in network) were derived using a dynamic approach (temporal fluctuations during acquisition). Network measures were compared between groups, with regions of significant difference correlated with known aberrant ocular motor VSS metrics (shortened latencies and higher number of inhibitory errors) in VSS patients. Lastly, nodal co-modularity, a binary measure of node pairs belonging to the same module, was studied. VSS patients had lower modularity, supramarginal centrality and LE dynamics of multiple (sub)cortical regions, centered around occipital and parietal lobules. In VSS patients, lateral occipital cortex LE dynamics correlated positively with shortened prosaccade latencies (p = .041, r = .353). In VSS patients, occipital, parietal, and motor nodes belonged more often to the same module and demonstrated lower nodal co-modularity with temporal and frontal regions. This study revealed reduced dynamic variation in modularity and local efficiency strength in the VSS brain, suggesting that brain network dynamics are less variable in terms of segregation and local clustering. Further investigation of these changes could inform our understanding of the pathogenesis of the disorder and potentially lead to treatment strategies.
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Affiliation(s)
- Myrte Strik
- Melbourne Brain Centre Imaging Unit, Department of Radiology, Melbourne Medical SchoolUniversity of MelbourneMelbourneVictoriaAustralia
| | - Meaghan Clough
- Department of Neuroscience, Central Clinical SchoolMonash UniversityMelbourneVictoriaAustralia
| | - Emma J. Solly
- Department of Neuroscience, Central Clinical SchoolMonash UniversityMelbourneVictoriaAustralia
| | - Rebecca Glarin
- Melbourne Brain Centre Imaging Unit, Department of Radiology, Melbourne Medical SchoolUniversity of MelbourneMelbourneVictoriaAustralia
| | - Owen B. White
- Department of Neuroscience, Central Clinical SchoolMonash UniversityMelbourneVictoriaAustralia
| | - Scott C. Kolbe
- Department of Neuroscience, Central Clinical SchoolMonash UniversityMelbourneVictoriaAustralia
| | - Joanne Fielding
- Department of Neuroscience, Central Clinical SchoolMonash UniversityMelbourneVictoriaAustralia
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15
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Graber M, Scutelnic A, Klein A, Puledda F, Goadsby PJ, Schankin CJ. Natural course of visual snow syndrome: a long-term follow-up study. Brain Commun 2022; 4:fcac230. [PMID: 36147453 PMCID: PMC9487631 DOI: 10.1093/braincomms/fcac230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/18/2022] [Accepted: 09/08/2022] [Indexed: 11/13/2022] Open
Abstract
Visual snow syndrome is characterized by a continuous visual disturbance resembling a badly tuned analogue television and additional visual and non-visual symptoms causing significant disability. The natural course of visual snow syndrome has not hitherto been studied. In this prospective longitudinal study, 78 patients with the diagnosis of visual snow syndrome made in 2011 were re-contacted in 2019 to assess symptom evolution using a semi-structured questionnaire. Forty patients (51% of 78) were interviewed after 84 ± 5 months (mean ± SD). In all patients, symptoms had persisted. Visual snow itself was less frequently rated as the most disturbing symptom (72 versus 42%, P = 0.007), whereas a higher proportion of patients suffered primarily from entopic phenomena (2 versus 17%, P = 0.024). New treatment was commenced in 14 (35%) patients, of whom in seven, visual snow syndrome was ameliorated somewhat. Three (7%) experienced new visual migraine aura without headache, and one (2%) had new migraine headache. There were no differences in the levels of anxiety and depression measured by the Patient Health Questionnaire 8 and the Generalized Anxiety Disorder Scale 7. Thirty-eight patients (49%) were lost to follow-up. In visual snow syndrome, symptoms can persist over 8 years without spontaneous resolution, although visual snow itself might become less bothersome.
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Affiliation(s)
- Michael Graber
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern , Bern 3010 , Switzerland
| | - Adrian Scutelnic
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern , Bern 3010 , Switzerland
| | - Antonia Klein
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern , Bern 3010 , Switzerland
| | - Francesca Puledda
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King’s College London SE1 1YR, London , UK
- NIHR-Wellcome Trust King’s Clinical Research Facility, SLaM Biomedical Research Center, King’s College London SE5 9PJ, London , UK
| | - Peter J Goadsby
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King’s College London SE1 1YR, London , UK
- NIHR-Wellcome Trust King’s Clinical Research Facility, SLaM Biomedical Research Center, King’s College London SE5 9PJ, London , UK
| | - Christoph J Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern , Bern 3010 , Switzerland
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16
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White OB, Fielding J, Pelak VS, Schankin CJ. Editorial: Visual Snow: Old Problem, New Understanding. Front Neurol 2022; 13:884752. [PMID: 35493832 PMCID: PMC9051336 DOI: 10.3389/fneur.2022.884752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Accepted: 03/14/2022] [Indexed: 12/04/2022] Open
Affiliation(s)
- Owen B. White
- Central Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC, Australia
- *Correspondence: Owen B. White
| | - Joanne Fielding
- Central Clinical School, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, VIC, Australia
| | | | - Christoph J. Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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17
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Puledda F, Villar-Martínez MD, Goadsby PJ. Case Report: Transformation of Visual Snow Syndrome From Episodic to Chronic Associated With Acute Cerebellar Infarct. Front Neurol 2022; 13:811490. [PMID: 35242098 PMCID: PMC8886039 DOI: 10.3389/fneur.2022.811490] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/24/2022] [Indexed: 12/23/2022] Open
Abstract
Visual snow syndrome is a novel neurological condition characterized by a panfield visual disturbance associated with several additional symptoms. Although it is usually a continuous and primary disorder, cases of intermittent visual snow have been described in the literature, as well as rare secondary forms. This report is the first description of a case of intermittent visual snow syndrome, which transformed into a persistent form following a posterior circulation stroke due to vertebral artery dissection. At 1 and 2 years after experiencing the acute cerebellar infarct, the patient's only neurological sequalae was visual snow. This case provides a description of how visual snow syndrome may be caused by an underlying brain disorder, and highlights the importance of the cerebellum in the pathophysiology of this relatively unknown condition. It further shows evidence of how existing predispositions might be relevant to the development of visual snow, in certain subjects and following specific circumstances.
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Affiliation(s)
- Francesca Puledda
- Headache Group, Wolfson Centre for Age-Related Diseases (CARD), SLaM Biomedical Research Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, National Institute for Health Research (NIHR)-Wellcome Trust King's Clinical Research Facility, King's College Hospital, London, United Kingdom
| | - María Dolores Villar-Martínez
- Headache Group, Wolfson Centre for Age-Related Diseases (CARD), SLaM Biomedical Research Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, National Institute for Health Research (NIHR)-Wellcome Trust King's Clinical Research Facility, King's College Hospital, London, United Kingdom
| | - Peter J Goadsby
- Headache Group, Wolfson Centre for Age-Related Diseases (CARD), SLaM Biomedical Research Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, National Institute for Health Research (NIHR)-Wellcome Trust King's Clinical Research Facility, King's College Hospital, London, United Kingdom.,Department of Neurology, University of California, Los Angeles, Los Angeles, CA, United States
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18
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Abstract
Purpose of Review Until the last 5 years, there was very little in the literature about the phenomenon now known as visual snow syndrome. This review will examine the current thinking on the pathology of visual snow and how that thinking has evolved. Recent Findings While migraine is a common comorbidity to visual snow syndrome, evidence points to these conditions being distinct clinical entities, with some overlapping pathophysiological processes. There is increasing structural and functional evidence that visual snow syndrome is due to a widespread cortical dysfunction. Cortical hyperexcitability coupled with changes in thalamocortical pathways and higher-level salience network controls have all shown differences in patients with visual snow syndrome compared to controls. Summary Further work is needed to clarify the exact mechanisms of visual snow syndrome. Until that time, treatment options will remain limited. Clinicians having a clearer understanding of the basis for visual snow syndrome can appropriately discuss the diagnosis with their patients and steer them towards appropriate management options.
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Affiliation(s)
- Clare L Fraser
- Faculty of Health and Medicine, Save Sight Institute, The University of Sydney, 8 Macquarie Street, Sydney, NSW, 2000, Australia. .,Macquarie Ophthalmology, School of Clinical Medicine, Macquarie University, Sydney, Australia.
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19
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Zito GA, Tarrano C, Jegatheesan P, Ekmen A, Béranger B, Rebsamen M, Hubsch C, Sangla S, Bonnet C, Delorme C, Méneret A, Degos B, Bouquet F, Brissard MA, Vidailhet M, Gallea C, Roze E, Worbe Y. Somatotopy of cervical dystonia in motor-cerebellar networks: Evidence from resting state fMRI. Parkinsonism Relat Disord 2021; 94:30-36. [PMID: 34875561 DOI: 10.1016/j.parkreldis.2021.11.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Revised: 11/25/2021] [Accepted: 11/29/2021] [Indexed: 01/15/2023]
Abstract
INTRODUCTION Cervical dystonia is the most frequent form of isolated focal dystonia. It is often associated with a dysfunction in brain networks, mostly affecting the basal ganglia, the cerebellum, and the somatosensory cortex. However, it is unclear if such a dysfunction is somato-specific to the brain areas containing the representation of the affected body part, and may thereby account for the focal expression of cervical dystonia. In this study, we investigated resting state functional connectivity in the areas within the motor cortex and the cerebellum containing affected and non-affected body representations in cervical dystonia patients. METHODS Eighteen patients affected by cervical dystonia and 21 healthy controls had resting state fMRI. The functional connectivity between the motor cortex and the cerebellum, as well as their corresponding measures of gray matter volume and cortical thickness, were compared between groups. We performed seed-based analyses, selecting the different body representation areas in the precentral gyrus as seed regions, and all cerebellar areas as target regions. RESULTS Compared to controls, patients exhibited increased functional connectivity between the bilateral trunk representation area of the motor cortex and the cerebellar vermis 6 and 7b, respectively. These functional abnormalities did not correlate with structural changes or symptom severity. CONCLUSIONS Our findings indicate that the abnormal function of the motor network is somato-specific to the areas encompassing the neck representation. Functional abnormalities in discrete relevant areas of the motor network could thus contribute to the focal expression of CD.
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Affiliation(s)
- Giuseppe A Zito
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Clément Tarrano
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Prasanthi Jegatheesan
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Asya Ekmen
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Benoît Béranger
- Center for NeuroImaging Research CENIR, Paris Brain Institute, Sorbonne University, UPMC Univ Paris 06, Inserm U1127, CNRS UMR 7225, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Michael Rebsamen
- Support Center for Advanced Neuroimaging SCAN, University Institute of Diagnostic and Interventional Neuroradiology, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010, Bern, CH, Switzerland.
| | - Cécile Hubsch
- Department of Neurology, Rothschild Foundation, 25-29 Rue Manin, 75019, Paris, France.
| | - Sophie Sangla
- Department of Neurology, Rothschild Foundation, 25-29 Rue Manin, 75019, Paris, France.
| | - Cécilia Bonnet
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Cécile Delorme
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Aurélie Méneret
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Bertrand Degos
- Neurology Unit, Assistance Publique-Hôpitaux de Paris, Avicenne University Hospital, Sorbonne Paris Nord, 125 Rue de Stalingrad, 93000, Bobigny, France; Center for Interdisciplinary Research in Biology, Collège de France, Inserm U1050, CNRS UMR 7241, PSL University, 11 place Marcelin Berthelot, 75231, Paris, France.
| | - Floriane Bouquet
- Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Marion Apoil Brissard
- Department of Neurology, University of Caen Normandie Hospital Center, Av. de la Côte de Nacre, 14000, Caen, France.
| | - Marie Vidailhet
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Cécile Gallea
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Emmanuel Roze
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurology, Assistance Publique-Hôpitaux de Paris, Pitié-Salpêtrière Hospital, 47-83 Boulevard de l'Hôpital, 75013, Paris, France.
| | - Yulia Worbe
- Sorbonne University, Inserm U1127, CNRS UMR7225, UM75, Paris Brain Institute, Movement Investigation and Therapeutics Team, 47-83 Boulevard de l'Hôpital, 75013, Paris, France; Department of Neurophysiology, Saint-Antoine Hospital, Assistance Publique-Hôpitaux de Paris, 184 Rue du Faubourg Saint-Antoine, 75012, Paris, France.
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20
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Puledda F, Vandenbussche N, Moreno-Ajona D, Eren O, Schankin C, Goadsby PJ. Evaluation of treatment response and symptom progression in 400 patients with visual snow syndrome. Br J Ophthalmol 2021; 106:1318-1324. [PMID: 34656983 PMCID: PMC9411880 DOI: 10.1136/bjophthalmol-2020-318653] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 03/24/2021] [Accepted: 03/26/2021] [Indexed: 11/03/2022]
Abstract
AIMS To gather information on useful medications to treat visual snow syndrome (VSS) as well as to validate an instrument to assess its clinical severity and the course of the disorder over time. METHODS Four hundred patients with VSS were included in this web-based prospective questionnaire study. All subjects completed a treatment questionnaire and a clinical diary. The first allowed evaluation of the effects of previous medications on visual snow, while the second measured VSS symptoms daily over the course of 30 days. RESULTS Patients commonly reported previous use of medications such as antidepressants, antiepileptics, antibiotics and benzodiazepines. However, none of these drug classes was beneficial for the majority of patients. Recreational drugs and alcohol worsened visual snow symptoms in several reports. Vitamins and benzodiazepines had high therapeutic ratios, although in most cases they did not change the course of VSS.The monthly diary confirmed that the static in VSS is a consistent symptom over time. It also showed that indoor and fluorescent lights have a worse effect on symptoms when compared with natural outdoor lighting. CONCLUSIONS The study confirms clinical experience that medications are generally ineffective in VSS, with the exception of vitamins and perhaps benzodiazepines, which could be beneficial in some patients. The 30-day diary represents a useful tool to measure symptom progression over time, which could be used in future trials on VSS.
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Affiliation(s)
- Francesca Puledda
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK .,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM Biomedical Research Centre, King's College Hospital, NIHR, London, UK
| | | | - David Moreno-Ajona
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM Biomedical Research Centre, King's College Hospital, NIHR, London, UK
| | - Ozan Eren
- Neurology, University Hospital LMU Munich, Munchen, Germany
| | | | - Peter J Goadsby
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM Biomedical Research Centre, King's College Hospital, NIHR, London, UK.,Neurology, University of California Los Angeles, Los Angeles, California, USA
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21
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Michels L, Stämpfli P, Aldusary N, Piccirelli M, Freund P, Weber KP, Fierz FC, Kollias S, Traber G. Widespread White Matter Alterations in Patients With Visual Snow Syndrome. Front Neurol 2021; 12:723805. [PMID: 34621237 PMCID: PMC8490630 DOI: 10.3389/fneur.2021.723805] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 08/04/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Visual snow is considered a disorder of central visual processing resulting in a perturbed perception of constant binocular flickering or pixilation of the whole visual field. The underlying neurophysiological and structural alterations remain elusive. Methods: In this study, we included patients (final n = 14, five dropouts; five females, mean age: 32 years) with visual snow syndrome (VSS) and age- and sex-matched controls (final n = 20, 6 dropouts, 13 females, mean age: 28.2 years). We applied diffusion tensor imaging to examine possible white matter (WM) alterations in patients with VSS. Results: The patient group demonstrated higher (p-corrected < 0.05, adjusted for age and sex) fractional anisotropy (FA) and lower mean diffusivity (MD) and radial diffusivity (RD) compared to controls. These changes were seen in the prefrontal WM (including the inferior fronto-occipital fascicle), temporal and occipital WM, superior and middle longitudinal fascicle, and sagittal stratum. When additionally corrected for migraine or tinnitus-dominant comorbidities in VSS-similar group differences were seen for FA and RD, but less pronounced. Conclusions: Our results indicate that patients with VSS present WM alterations in parts of the visual cortex and outside the visual cortex. As parts of the inferior fronto-occipital fascicle and sagittal stratum are associated with visual processing and visual conceptualisation, our results suggest that the WM alterations in these regions may indicate atypical visual processing in patients with VSS. Yet, the frequent presence of migraine and other comorbidities such as tinnitus in VSS makes it difficult to attribute WM disruptions solely to VSS.
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Affiliation(s)
- Lars Michels
- Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Philipp Stämpfli
- Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Zurich, Switzerland
| | - Njoud Aldusary
- Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich, Switzerland.,Department of Diagnostic Radiology, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Marco Piccirelli
- Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | | | - Konrad P Weber
- Department of Neurology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Fabienne C Fierz
- Department of Ophthalmology, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Spyros Kollias
- Department of Neuroradiology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich, Switzerland
| | - Ghislaine Traber
- Institute of Molecular and Clinical Ophthalmology Basel (IOB), Basel, Switzerland.,Department of Ophthalmology, University of Basel, Basel, Switzerland
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22
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Foletta PJ, Clough M, McKendrick AM, Solly EJ, White OB, Fielding J. Delayed Onset of Inhibition of Return in Visual Snow Syndrome. Front Neurol 2021; 12:738599. [PMID: 34603190 PMCID: PMC8484518 DOI: 10.3389/fneur.2021.738599] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/11/2021] [Indexed: 11/22/2022] Open
Abstract
Visual snow syndrome (VSS) is a complex, sensory processing disorder. We have previously shown that visual processing changes manifest in significantly faster eye movements toward a suddenly appearing visual stimulus and difficulty inhibiting an eye movement toward a non-target visual stimulus. We propose that these changes reflect poor attentional control and occur whether attention is directed exogenously by a suddenly appearing event, or endogenously as a function of manipulating expectation surrounding an upcoming event. Irrespective of how attention is captured, competing facilitatory and inhibitory processes prioritise sensory information that is important to us, filtering out that which is irrelevant. A well-known feature of this conflict is the alteration to behaviour that accompanies variation in the temporal relationship between competing sensory events that manipulate facilitatory and inhibitory processes. A classic example of this is the “Inhibition of Return” (IOR) phenomenon that describes the relative slowing of a response to a validly cued location compared to invalidly cued location with longer cue/target intervals. This study explored temporal changes in the allocation of attention using an ocular motor version of Posner's IOR paradigm, manipulating attention exogenously by varying the temporal relationship between a non-predictive visual cue and target stimulus. Forty participants with VSS (20 with migraine) and 20 controls participated. Saccades were generated to both validly cued and invalidly cued targets with 67, 150, 300, and 500 ms cue/target intervals. VSS participants demonstrated delayed onset of IOR. Unlike controls, who exhibited IOR with 300 and 500 ms cue/target intervals, VSS participants only exhibited IOR with 500 ms cue/target intervals. These findings provide further evidence that attention is impacted in VSS, manifesting in a distinct saccadic behavioural profile, and delayed onset of IOR. Whether IOR is perceived as the build-up of an inhibitory bias against returning attention to an already inspected location or a consequence of a stronger attentional orienting response elicited by the cue, our results are consistent with the proposal that in VSS, a shift of attention elicits a stronger increase in saccade-related activity than healthy controls. This work provides a more refined saccadic behavioural profile of VSS that can be interrogated further using sophisticated neuroimaging techniques and may, in combination with other saccadic markers, be used to monitor the efficacy of any future treatments.
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Affiliation(s)
- Paige J Foletta
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Meaghan Clough
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Allison M McKendrick
- Department of Optometry and Vision Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Emma J Solly
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Owen B White
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
| | - Joanne Fielding
- Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia
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Klein A, Schankin CJ. Visual Snow Syndrome as a Network Disorder: A Systematic Review. Front Neurol 2021; 12:724072. [PMID: 34671311 PMCID: PMC8521005 DOI: 10.3389/fneur.2021.724072] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 08/31/2021] [Indexed: 11/13/2022] Open
Abstract
Aim: By reviewing the existing clinical studies about visual snow (VS) as a symptom or as part of visual snow syndrome (VSS), we aim at improving our understanding of VSS being a network disorder. Background: Patients with VSS suffer from a continuous visual disturbance resembling the view of a badly tuned analog television (i.e., VS) and other visual, as well as non-visual symptoms. These symptoms can persist over years and often strongly impact the quality of life. The exact prevalence is still unknown, but up to 2.2% of the population could be affected. Presently, there is no established treatment, and the underlying pathophysiology is unknown. In recent years, there have been several approaches to identify the brain areas involved and their interplay to explain the complex presentation. Methods: We collected the clinical and paraclinical evidence from the currently published original studies on VS and its syndrome by searching PubMed and Google Scholar for the term visual snow. We included original studies in English or German and excluded all reviews, case reports that did not add new information to the topic of this review, and articles that were not retrievable in PubMed or Google Scholar. We grouped the studies according to the methods that were used. Results: Fifty-three studies were found for this review. In VSS, the clinical spectrum includes additional visual disturbances such as excessive floaters, palinopsia, nyctalopia, photophobia, and entoptic phenomena. There is also an association with other perceptual and affective disorders as well as cognitive symptoms. The studies that have been included in this review demonstrate structural, functional, and metabolic alterations in the primary and/or secondary visual areas of the brain. Beyond that, results indicate a disruption in the pre-cortical visual pathways and large-scale networks including the default mode network and the salience network. Discussion: The combination of the clinical picture and widespread functional and structural alterations in visual and extra-visual areas indicates that the VSS is a network disorder. The involvement of pre-cortical visual structures and attentional networks might result in an impairment of "filtering" and prioritizing stimuli as top-down process with subsequent excessive activation of the visual cortices when exposed to irrelevant external and internal stimuli. Limitations of the existing literature are that not all authors used the ICHD-3 definition of the VSS. Some were referring to the symptom VS, and in many cases, the control groups were not matched for migraine or migraine aura.
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Affiliation(s)
| | - Christoph J. Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Klein A, Schankin CJ. Visual snow syndrome, the spectrum of perceptual disorders, and migraine as a common risk factor: A narrative review. Headache 2021; 61:1306-1313. [PMID: 34570907 PMCID: PMC9293285 DOI: 10.1111/head.14213] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/06/2021] [Accepted: 08/19/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The aim of this narrative review is to explore the relationship between visual snow syndrome (VSS), migraine, and a group of other perceptual disorders. BACKGROUND VSS is characterized by visual snow and additional visual and nonvisual disturbances. The clinical picture suggests a hypersensitivity to internal and external stimuli. Imaging and electrophysiological findings indicate a hyperexcitability of the primary and secondary visual areas of the brain possibly due to an impairment of inhibitory feedback mechanisms. Migraine is the most frequent comorbidity. Epidemiological and clinical studies indicate that other perceptual disorders, such as tinnitus, fibromyalgia, and dizziness, are associated with VSS. Clinical overlaps and parallels in pathophysiology might exist in relation to migraine. METHODS We performed a PubMed and Google Scholar search with the following terms: visual snow syndrome, entoptic phenomenon, fibromyalgia, tinnitus, migraine, dizziness, persistent postural-perceptual dizziness (PPPD), comorbidities, symptoms, pathophysiology, thalamus, thalamocortical dysrhythmia, and salience network. RESULTS VSS, fibromyalgia, tinnitus, and PPPD share evidence of a central disturbance in the processing of different stimuli (visual, somatosensory/pain, acoustic, and vestibular) that might lead to hypersensitivity. Imaging and electrophysiological findings hint toward network disorders involving the sensory networks and other large-scale networks involved in the management of attention and emotional processing. There are clinical and epidemiological overlaps between these disorders. Similarly, migraine exhibits a multisensory hypersensitivity even in the interictal state with fluctuation during the migraine cycle. All the described perceptual disorders are associated with migraine suggesting that having migraine, that is, a disorder of sensory processing, is a common link. CONCLUSION VSS, PPPD, fibromyalgia, and chronic tinnitus might lie on a spectrum of perceptual disorders with similar pathophysiological mechanisms and the common risk factor migraine. Understanding the underlying network disturbances might give insights into how to improve these currently very difficult to treat conditions.
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Affiliation(s)
- Antonia Klein
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Christoph J Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Puledda F, Schankin CJ, O'Daly O, Ffytche D, Eren O, Karsan N, Williams SCR, Zelaya F, Goadsby PJ. Localised increase in regional cerebral perfusion in patients with visual snow syndrome: a pseudo-continuous arterial spin labelling study. J Neurol Neurosurg Psychiatry 2021; 92:918-926. [PMID: 34261750 PMCID: PMC8372400 DOI: 10.1136/jnnp-2020-325881] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 06/09/2021] [Indexed: 12/11/2022]
Abstract
OBJECTIVES We aimed to investigate changes in regional cerebral blood flow (rCBF) using arterial spin labelling (ASL) in patients with visual snow syndrome (VSS), in order to understand more about the underlying neurobiology of the condition, which remains mostly unknown. METHODS We performed an MRI study in which whole-brain maps of rCBF were obtained using pseudo-continuous ASL. Twenty-four patients with VSS and an equal number of gender and age-matched healthy volunteers took part in the study. All subjects were examined with both a visual paradigm consisting of a visual-snow like stimulus, simulating key features of the snow, and a blank screen at rest, randomly presented. RESULTS Patients with VSS had higher rCBF than controls over an extensive brain network, including the bilateral cuneus, precuneus, supplementary motor cortex, premotor cortex and posterior cingulate cortex, as well as the left primary auditory cortex, fusiform gyrus and cerebellum. These areas were largely analogous comparing patients either at rest, or when looking at a 'snow-like' visual stimulus. This widespread, similar pattern of perfusion differences in either condition suggests a neurophysiological signature of visual snow. Furthermore, right insula rCBF was increased in VSS subjects compared with controls during visual stimulation, reflecting a greater task-related change and suggesting a difference in interoceptive processing with constant perception of altered visual input. CONCLUSION The data suggest VSS patients have marked differences in brain processing of visual stimuli, validating its neurobiological basis.
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Affiliation(s)
- Francesca Puledda
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, King's College London, London, UK .,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM NIHR Biomedical Research Centre, King's College Hospital, London, UK
| | - Christoph J Schankin
- Department of Neurology, Inselspital University Hospital Bern, Bern, Switzerland
| | - Owen O'Daly
- Centre for Neuroimaging Sciences, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Dominic Ffytche
- Old Age Psychiatry, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Ozan Eren
- Department of Neurology, University Hospital Munich Campus Grosshadern, Munchen, Germany
| | - Nazia Karsan
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, King's College London, London, UK
| | - Steve C R Williams
- Centre for Neuroimaging Sciences, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Fernando Zelaya
- Centre for Neuroimaging Sciences, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Peter J Goadsby
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology & Neuroscience, King's College London, King's College London, London, UK.,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM NIHR Biomedical Research Centre, King's College Hospital, London, UK
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Ciuffreda KJ, Han ME, Tannen B, Rutner D. Visual snow syndrome: evolving neuro-optometric considerations in concussion/mild traumatic brain injury. Concussion 2021; 6:CNC89. [PMID: 34084555 PMCID: PMC8162163 DOI: 10.2217/cnc-2021-0003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Kenneth J Ciuffreda
- SUNY/College of Optometry, University Eye Center, Vision Rehabilitation Service, New York, NY 10036, USA
| | - Mh Esther Han
- SUNY/College of Optometry, University Eye Center, Vision Rehabilitation Service, New York, NY 10036, USA
| | - Barry Tannen
- SUNY/College of Optometry, University Eye Center, Vision Rehabilitation Service, New York, NY 10036, USA
| | - Daniella Rutner
- SUNY/College of Optometry, University Eye Center, Vision Rehabilitation Service, New York, NY 10036, USA
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Puledda F, O'Daly O, Schankin C, Ffytche D, Williams SC, Goadsby PJ. Disrupted connectivity within visual, attentional and salience networks in the visual snow syndrome. Hum Brain Mapp 2021; 42:2032-2044. [PMID: 33448525 PMCID: PMC8046036 DOI: 10.1002/hbm.25343] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 12/11/2020] [Accepted: 01/04/2021] [Indexed: 01/22/2023] Open
Abstract
Here we investigate brain functional connectivity in patients with visual snow syndrome (VSS). Our main objective was to understand more about the underlying pathophysiology of this neurological syndrome. Twenty‐four patients with VSS and an equal number of gender and age‐matched healthy volunteers attended MRI sessions in which whole‐brain maps of functional connectivity were acquired under two conditions: at rest while watching a blank screen and during a visual paradigm consisting of a visual‐snow like stimulus. Eight unilateral seed regions were selected a priori based on previous observations and hypotheses; four seeds were placed in key anatomical areas of the visual pathways and the remaining were derived from a pre‐existing functional analysis. The between‐group analysis showed that patients with VSS had hyper and hypoconnectivity between key visual areas and the rest of the brain, both in the resting state and during a visual stimulation, compared with controls. We found altered connectivity internally within the visual network; between the thalamus/basal ganglia and the lingual gyrus; between the visual motion network and both the default mode and attentional networks. Further, patients with VSS presented decreased connectivity during external sensory input within the salience network, and between V5 and precuneus. Our results suggest that VSS is characterised by a widespread disturbance in the functional connectivity of several brain systems. This dysfunction involves the pre‐cortical and cortical visual pathways, the visual motion network, the attentional networks and finally the salience network; further, it represents evidence of ongoing alterations both at rest and during visual stimulus processing.
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Affiliation(s)
- Francesca Puledda
- Headache Group, Department of Basic and Clinical Neuroscience, King's College London, London, United Kingdom.,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM NIHR Biomedical Research Centre, King's College Hospital, London, United Kingdom
| | - Owen O'Daly
- Centre for Neuroimaging Sciences, Department of Neuroimaging, King's College London, London, United Kingdom
| | - Christoph Schankin
- Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Dominic Ffytche
- Department of Old Age Psychiatry, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Steven Cr Williams
- Centre for Neuroimaging Sciences, Department of Neuroimaging, King's College London, London, United Kingdom
| | - Peter J Goadsby
- Headache Group, Department of Basic and Clinical Neuroscience, King's College London, London, United Kingdom.,NIHR-Wellcome Trust King's Clinical Research Facility, SLaM NIHR Biomedical Research Centre, King's College Hospital, London, United Kingdom
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