Abstract
Since the first description of visual snow syndrome (VSS) in 1995, there has been increasing interest particularly within the past 5-10 years in phenotyping the condition and differentiating it from conditions such as migraine with aura and hallucinogen persisting perception disorder. Structural and functional neuroimaging has provided valuable insights in this regard, yielding functional networks and anatomical regions of interest, of which the right lingual gyrus is of particular note. Various modalities, including functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and single photon emission computed tomography (SPECT), have all been studied in patients with visual snow. In this article, we conduct a comprehensive literature review of neuroimaging in VSS.
Highlights
The clinical manifestations of visual snow syndrome (VSS) were first described by Liu et al in 1995, who reported a cohort of ten patients with persistent positive visual phenomena that lasted from two months to five years without evidence of migrainous infarction [1]
2.1.2 Increased Gray Matter Volume Increased gray matter volume (GMV) in the lingual gyrus has been found on volumetric MRI in 19 patients with VSS compared to 16 controls [5]
This study found increased GMV in the right middle temporal gyrus, right parahippocampal gyrus, and right anterior cingulate cortex, though these did not have abnormal findings on positron emission tomography (PET)
Summary
The clinical manifestations of visual snow syndrome (VSS) were first described by Liu et al in 1995, who reported a cohort of ten patients with persistent positive visual phenomena that lasted from two months to five years without evidence of migrainous infarction [1]. The symptoms reported included positive visual hallucinations of simple geometric forms, transient loss of vision, as well as more complex visual distortions including palinopsia and associated altered body perceptions [1]. Since this first report, there has been increasing interest in the condition phenomenologically and it was first formally described as visual snow in 2014 [2, 3]. Increasing research, and employment of advanced neuro-imaging has provided invaluable insights into VSS. This article reviews the literature of neuro-imaging in VSS, providing a summary of abnormal findings (Table 1) and discusses possible insights for the condition
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