Objective: Visual snow (VS) is a distressing, life-impacting condition with persistent visual phenomena. VS patients show cerebral hypermetabolism within the visual cortex, resulting in altered neuronal excitability. We hypothesized to see disease-dependent alterations in functional connectivity and gray matter volume (GMV) in regions associated with visual perception. Methods: Nineteen patients with VS and 16 sex-and age-matched controls were recruited. Functional magnetic resonance imaging (fMRI) was applied to examine resting-state functional connectivity (rsFC). Volume changes were assessed by means of voxel-based morphometry (VBM). Finally, we assessed associations between MRI indices and clinical parameters. Results: Patients with VS showed hyperconnectivity between extrastriate visual and inferior temporal brain regions and also between prefrontal and parietal (angular cortex) brain regions (p < 0.05, corrected for age and migraine occurrence). In addition, patients showed increased GMV in the right lingual gyrus (p < 0.05 corrected). Symptom duration positively correlated with GMV in both lingual gyri (p < 0.01 corrected). Conclusion: This study found VS to be associated with both functional and structural changes in the early and higher visual cortex, as well as the temporal cortex. These brain regions are involved in visual processing, memory, spatial attention, and cognitive control. We conclude that VS is not just confined to the visual system and that both functional and structural changes arise in VS patients, be it as an epiphenomenon or a direct contributor to the pathomechanism of VS. These in vivo neuroimaging biomarkers may hold potential as objective outcome measures of this so far purely subjective condition.

Background The optimization of magnetic resonance spectroscopy (MRS) sequences allows improved diagnosis and prognosis of neurological and psychological disorders. Thus, to assess the test–retest and intersequence reliability of such MRS sequences in quantifying metabolite concentrations is of clinical relevance. Purpose To evaluate the test–retest and intersequence reliability of three MRS sequences to estimate GABA and Glx = Glutamine+Glutamate concentrations in the human brain. Study Type Prospective. Subjects Eighteen healthy participants were scanned twice (range: 1 day to 1 week between the two sessions) with identical protocols. Field Strength/Sequence 3T using a 32‐channel SENSE head coil in the PCC region; PRESS, JPRESS, and MEGA‐PRESS sequences. Assessment Metabolite concentrations were estimated using LCModel (for PRESS and MEGA‐PRESS) and ProFit2 (for JPRESS). Statistical Tests The test–retest reliability was evaluated by Wilcoxon signed‐rank tests, Pearson's r correlation coefficients, intraclass‐correlation coefficients (ICC), coefficients of variation (CV), and by Bland–Altman (BA) plots. The intersequence reliability was assessed with Wilcoxon signed‐rank tests, Pearson's r correlation coefficients, and BA plots. Results For GABA, only the MEGA‐PRESS sequence showed a moderate test–retest correlation (r = 0.54, ICC = 0.5, CV = 8.8%) and the BA plots indicated good agreement (P > 0.05) for all sequences. JPRESS provided less precise results and PRESS was insensitive to GABA. For Glx, the r and ICC values for PRESS (r = 0.87, ICC = 0.9, CV = 2.9%) and MEGA‐PRESS (r = 0.70, ICC = 0.7, CV = 5.3%) reflect higher correlations, compared with JPRESS (r = 0.39, ICC = 0.4, CV = 20.1%). Data Conclusion MEGA‐PRESS and JPRESS are suitable for the reliable detection of GABA, the first being more precise. The three sequences included in the study can measure Glx concentrations. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1181–1191.

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