Amyotrophic Lateral Sclerosis with SOD1 mutations shows distinct brain metabolic changes

Purpose. Neuropathological data suggest that ALS with SOD1 mutations (SOD1-ALS) is a distinct form of ALS. We evaluated brain metabolic changes characterizing SOD1-ALS as compared to sporadic ALS (sALS), employing 18F-FDG-PET. Methods. We included 18 SOD1-ALS patients, 40 healthy controls (HC), and 46 sALS patients without mutations in SOD1, TARDBP, FUS, and C9ORF72, randomly selected from 665 subjects who underwent brain 18F-FDG-PET at diagnosis between 2008 and 2019 at the ALS Centre of Turin. We excluded patients with Frontotemporal Dementia. We used the full factorial design in SPM12 to evaluate whether differences among groups exist overall. In case the hypothesis was confirmed, group comparisons were performed through the two-sample t-test model of SPM12. In all the analyses the height threshold was P<0.001 (P<0.05 FWE-corrected at cluster level). Results. The full factorial design resulted in a significant main effect of groups. We identified a relative hypometabolism in sALS patients compared to SOD1-ALS cases in right precentral and medial frontal gyrus, right paracentral lobule, and bilateral postcentral gyrus. SOD1 patients showed a relative hypermetabolism as compared to HC in right precentral gyrus and paracentral lobule. As compared to HC, sALS patients showed relative hypometabolism in frontal, temporal and occipital cortices. Conclusion. SOD1-ALS was characterized by a relative hypermetabolism in motor cortex as compared to sALS and HC. Since promising, targeted, therapeutic strategies are upcoming for SOD1-ALS, our data support the use of PET to study disease pathogenesis and to track its course in clinical trials, both in asymptomatic and symptomatic mutation carriers.