Simultaneous 18F-FDG PET/MR metabolic and structural changes in visual snow syndrome and diagnostic use

Abstract

Purpose Visual snow syndrome (VSS) is a recently recognized chronic neurologic condition characterized by the constant perceiving of tiny flickering dots throughout the entire visual field. Metabolic overactivity and grey matter volume increase in the lingual gyrus has been reported. We investigated this by 18F-FDG PET/MR in comparison to healthy controls. Aside from voxel-based characterization, the classification accuracy of volume-of-interest (VOI)-based multimodal assessment was evaluated, also in comparison with visual analysis. Methods Simultaneous 18F-FDG PET and MR imaging was performed in 7 patients with VSS (24.6 ± 5.7 years; 5 M/2F) and 15 age-matched healthy controls (CON) (28.0 ± 5.3 years; 8 M/7F). SPM12 and voxel-based morphometric analysis was performed. A VOI-based discriminant analysis was performed with relative 18F-FDG uptake, MR grey matter (GM) volumes and their combination. A visual analysis was done by two blinded experienced readers. Results Relative increased hypermetabolism was found in VSS patients in the lingual gyrus and cuneus (pFWE < 0.05, peak change + 24%), and hypometabolism in the mesiotemporal cortex (pheight,uncorr < 0.001, peak change − 14%). VSS patients also had increased GM volume in the limbic system and frontotemporal cortex bilaterally (pFWE < 0.05), and in the left secondary and associative visual cortex and in the left lingual gyrus (pheight,uncorr < 0.001). Discriminant analysis resulted in 100% correct classification accuracy for 18F-FDG with lingual gyrus, cuneus and lateral occipital lobe (BA 17 and BA 18) as main discriminators. Unimodal MR- and combined 18F-FDG + MR classification resulted in an accuracy of 91% and 95%, respectively. Visual analysis of 18F-FDG was highly observer dependent. Conclusion Patients with VSS have highly significant structural and metabolic abnormalities in the visual and limbic system. VOI-based discriminant analysis of 18F-FDG PET allows reliable individual classification versus controls, whereas visual analysis of experienced observers was highly variable. Further investigation in larger series, also in comparison to VSS mimicking disorders such as migraine, is warranted. Trail registration: Retrospectively registered at clinicaltrials.gov under NCT05569733 on Oct 5, 2022.

Visual snow syndrome: recent advances in understanding the pathophysiology and potential treatment approaches

“…Van Laere et al [19] conducted an FDG-PET/ MRI study demonstrating hypermetabolism in secondary visual brain areas (lingual gyrus and cuneus), aligning with previous findings [8,9], as well as increased gray matter volume in the left secondary and associative visual cortex and in the left lingual gyrus. Additionally, hypometabolism in the mesiotemporal cortex and increased gray matter volume in frontotemporal areas, including components of the limbic system, were found [19].…”

Visual Snow is Alleviated by Adapting to Visual Noise

“…Which specific regions give rise to the visual snow percept remains unclear. Visual cortex in people with VSS appears to be more active at rest 18,20 , to be sending stronger signals to other parts of the brain at rest 13,14,16 and to have increased grey matter volume 14,15,18,20 compared to normally sighted controls. The lingual gyrus, found on the ventral surface of the occipital lobe, shows these differences most consistently [13][14][15]18,20 , and probably supports mid-level visual processing.…”

“…Visual cortex in people with VSS appears to be more active at rest 18,20 , to be sending stronger signals to other parts of the brain at rest 13,14,16 and to have increased grey matter volume 14,15,18,20 compared to normally sighted controls. The lingual gyrus, found on the ventral surface of the occipital lobe, shows these differences most consistently [13][14][15]18,20 , and probably supports mid-level visual processing. However, comorbid symptoms associated with visual snow (e.g., photophobia, palinopsia, tinnitus, and migraine) make it difficult to determine whether reported differences are due to visual snow specifically.…”

“…mechanisms producing VSS, other than it originates beyond the retina, which appears normal [9][10][11][12] . Accordingly, visual cortex is a likely origin [13][14][15][16][17][18][19][20] .…”

Alterations of the Alpha Rhythm in Visual Snow Syndrome: A Case-Control Study

“…In neuroimaging, individuals affected by VSS show functional and structural differences in various areas of the visual system, higher-order attentional networks and in the limbic system (7)(8)(9)(10)(11).…”