Description of the Neurovisual and Radiological Specificities of Patients With Visual Snow Syndrome

Study Overview
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Brief Summary
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NEVICOG is a single-center study evaluating neurovisual and radiological specificities in patients with visual snow syndrome (VSS) compared to a control population.

Detailed Description
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Visual snow syndrome (SNV) is characterized by a continuous grainy or pixelated visual sensation additional to the perceived image. Patients often report a feeling similar to seeing noise from cathode-ray televisions. The prevalence is not well known but about 2% of the population could be reached. Although benign and stable, this pathology is often troublesome in everyday life. Its precise etiology remains unknown to this day. Ophthalmologic explorations do not reveal any significant abnormalities. Neurologically, standard examinations appear normal. Only the examinations carried out in the context of research have been able to highlight anomalies such as an imbalance between visual cortical inhibition and excitation as well as a high spontaneous neural triggering and hypermetabolism of the associative visual cortex (functional MRI, PET- MRI). In addition, the Visual Evoked Potentials show a lack of habituation, testifying to cortical hyperexcitability. To our knowledge, no specific neurovisual study focusing on the functions involved in the processing of visual information has been carried out to date. We propose the realization of a complete evaluation made up of existing tasks as well as the adaptation of some of them specific to SNV. The posterior abnormalities currently highlighted by imaging have been carried out in examinations not available on a daily basis. A non-invasive brain MRI study will be carried out in our patients using more recent techniques (MRI with arterial spin labelling or ASL for Arterial Spin Labelling, and diffusion tensor imaging or DTI for Diffusion Tensor Imaging) in order to search for possible posterior lesions and clinical radiological correlations. Thus, this study aims to carry out a more in-depth neurovisual exploration of this syndrome, in order to allow a better understanding of this frequent and disabling disorder on a daily basis.

Official Title
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Description of the Neurovisual and Radiological Specificities of Patients With Visual Snow

Conditions
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Visual Snow Syndrome

Intervention / Treatment
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* Procedure: Neurovisual evaluation
* Procedure: Cerebral MRI


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Case group: Patient aged up to 55 Diagnosis of visual snow syndrome according to the international criteria Visual snow symptoms still present Express consent to participate in the study Control group: Person aged up to 60 Matched to an SNV patient on age (+/- 5 years) and sex Express consent to participate in the study Exclusion Criteria: Case group: Patient with an absolute or relative contraindication to MRI (claustrophobia, incompatible implantable device, etc.) Patient benefiting from a legal protection measure Pregnant or breastfeeding woman Non-French speaking patient Added psychiatric or neurodegenerative pathology unrelated to visual snow likely to induce neurocognitive and neurovisual disorders in the short or long term Ophthalmologic comorbidity that may interfere with the interpretation of examinations Control group: Patient with an absolute or relative contraindication to MRI (claustrophobia, incompatible implantable device, etc.) Person benefiting from a legal protection measure Pregnant or breastfeeding woman Non-French speaking person Psychiatric or neurodegenerative pathology likely to induce neurocognitive and neurovisual disorders in the short or long term Ophthalmologic comorbidity that may interfere with the interpretation of examinations

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Case group<br>Patients with visual snow syndrome according to international criteria | Procedure: Neurovisual evaluation<br>* Standardized tests and scales classically used during a neurovisual evaluation,<br>Procedure: Cerebral MRI<br>* Sequences realized : 3D T1 TFE i1.0 3D FLAIR i1.0 2D T2 0.3 coro, centré sur les orbites 3D T2 i0.6 SWIp 0.6 3D PD T2 NO, centré sur les orbites 3D ASL DTI 64dir<br>|
| Control group<br>Patients without visual snow syndrome according to international criteria | Procedure: Neurovisual evaluation<br>* Standardized tests and scales classically used during a neurovisual evaluation,<br>Procedure: Cerebral MRI<br>* Sequences realized : 3D T1 TFE i1.0 3D FLAIR i1.0 2D T2 0.3 coro, centré sur les orbites 3D T2 i0.6 SWIp 0.6 3D PD T2 NO, centré sur les orbites 3D ASL DTI 64dir<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Results of the neurovisual assessment | Rey-Osterrieth test will be used to assess the neurovisual ability. Patients have to reproduce a figure composed of 18 elements. A score between 0 and 2 is given to each of these elements according to their accuracy. The score varies from 0 to 36 and assesses the patient's visuo-constructive ability (36 corresponds to the best visuo-constructive ability). | 1 day (Inclusion) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Visual Snow Syndrome