Simultaneous Fluorodeoxyglucose Positron Emission Tomography (PET) and Magnetic Resonance (MR) in Visual Snow Syndrome

Study Overview
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Brief Summary
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Visual snow syndrome (VSS) is a neurologic condition where patients experience tiny flickering dots in their entire visual field. It has been reported that the brain consumes more glucose in the lingual gyrus (a subdivision of the occipital cortex) and that this also shows increased volume of grey matter (neurons and supporting cells). In this study, the investigators apply fluor-18 fluorodeoxyglucose positron emission tomography with magnetic resonance imaging (18F-FDG PET/MR) in patients with VSS and compare this to healthy controls. Aside from an analysis in each brain volume element (voxel), the accuracy of classifying groups based on a volume-of-interest (VOI) analysis of both PET and MR is studied, Lastly, this is also compared to a visual assessment of the PET and MR images.

Detailed Description
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Aim : Prospective measurement of brain glucose metabolism and structural integrity in the brain of subjects with visual snow syndrome (VSS). Voxel-based and volume-of interest comparison to age matched healthy controls retrospectively obtained on the same simultaneous PET/MR imaging system. Hypothesis : 1/ VSS patients show overactivation of parts of the visual system, in particular the lingual gyrus, which is likely related to larger volume of the gyrus on structural imaging. 2/ Discrimination of VSS patients versus controls can be done by visual read of FDG PET and/or volume-of-interest based discriminant analysis. Methods : Recruitment through neurology practice specialised in VSS, detailed history taking and assessment of in/exclusion criteria, scanning with simultaneous18F-FDG PET/MR Signa GE Healthcare. Analysis : visual assessment, group-based voxel and volume-of-interest based analysis (FDG PET, volumetry T1 MRI) with appropriate statistics and corrections for multiple regional comparisons. Discriminant analysis on VOI based data. Dual observer scoring of visual data and assessment of accuracy, sensitivity and specificity of visual image analysis compared to clinical final diagnosis.

Official Title
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Simultaneous Fluorodeoxyglucose and Magnetic Resonance Imaging (18F-FDG PET/MR) Study of Metabolic and Structural Changes in Visual Snow Syndrome Compared to Healthy Controls

Conditions
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Visual Snow Syndrome

Intervention / Treatment
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* Diagnostic Test: simultaneous fluor-18 fluorodeoxyglucose (FDG) positron emission tomography with magnetic resonance imaging (PET/MRI)


Participation Criteria
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Eligibility Criteria
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GROUP 1: VSS Patients Inclusion Criteria: M/F, age 18-85, diagnosis of VSS by an experienced neurologist : dynamic, continuous, black and white tiny dots in the entire visual field lasting longer than 3 months, with at least two additional visual symptoms Exclusion Criteria: - other underlying neurological conditions inclusive ophthalmological examinations GROUP 2 : Controls Inclusion Criteria: age 18-85 years, M/F, in general healthy condition normal neurological examination, Mini-Mental State Examination (MMSE) ≥ 28, Beck's Depression Inventory (BDI) score ≤ 9, and a normal structural volumetric MRI. Exclusion Criteria: history of major internal pathology, neurological and/or psychiatric disorders (including psychosis, depression, and anxiety), history of frequent migraine attacks, substance abuse or current use of any central acting medication first-degree relatives with dementia.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 85 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| VSS<br>Patients with visual snow syndrome | Diagnostic Test: simultaneous fluor-18 fluorodeoxyglucose (FDG) positron emission tomography with magnetic resonance imaging (PET/MRI)<br>* All subjects fast at least for 4 hours prior to 18F-FDG injection. 18F-FDG is injected intravenously (150 megabecquerel (MBq)) in standard ambient conditions, supine in a dark, noise free room with eyes and ears open. 18F-FDG PET images are acquired for 20 min on a simultaneous GE Signa 3 Tesla (3T) PET/MR scanner with integrated Time-of-Flight (TOF) (GE Healthcare, Chicago, USA). Simultaneous with the 18F-FDG PET/MR acquisition, zero-echo-time (ZTE) MR data are acquired for attenuation correction and a 3D volumetric T1-weighted BRAVO MR sequence using a vendor supplied high-resolution 8-channel phased array head coil (GE Healthcare, Milwaukee, USA).<br>|
| controls<br>healthy, screened age-matched controls | Diagnostic Test: simultaneous fluor-18 fluorodeoxyglucose (FDG) positron emission tomography with magnetic resonance imaging (PET/MRI)<br>* All subjects fast at least for 4 hours prior to 18F-FDG injection. 18F-FDG is injected intravenously (150 megabecquerel (MBq)) in standard ambient conditions, supine in a dark, noise free room with eyes and ears open. 18F-FDG PET images are acquired for 20 min on a simultaneous GE Signa 3 Tesla (3T) PET/MR scanner with integrated Time-of-Flight (TOF) (GE Healthcare, Chicago, USA). Simultaneous with the 18F-FDG PET/MR acquisition, zero-echo-time (ZTE) MR data are acquired for attenuation correction and a 3D volumetric T1-weighted BRAVO MR sequence using a vendor supplied high-resolution 8-channel phased array head coil (GE Healthcare, Milwaukee, USA).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Group difference in regional brain metabolism as assessed with 18F-FDG positron emission tomography | Visual, voxel- and volume-of-interest based assessment of of FDG PET | analysis done immediately after imaging | 
| Group difference in regional brain volume assessed with volumetric magnetic resonance imaging. | Visual, voxel- and volume-of-interest based assessment of MRI images | at baseline | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Discriminant analysis of PET metabolic differences | Statistical discriminant analysis of FDG between VSS patients and controls | at baseline | 
| Visual scoring of PET metabolic differences | Visual scoring of FDG between VSS patients and controls | at baseline | 
| Discriminant analysis of MR volumetric differences | Statistical discriminant analysis of regional MR volumetry between VSS patients and controls | at baseline | 
| Visual scoring of MR volumetric differences | Visual scoring of regional MR volumetry between VSS patients and controls | at baseline | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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FDG PET, PET/MR, volumetry, visual analysis, discriminant analysis