Prognostic power of psoas muscles structure and metabolism in amyotrophic lateral sclerosi

Aim/Introduction: Amyotrophic lateral sclerosis (ALS) is a lethal degeneration of upper and lower motor neurons. Median survival, from onset to death, is extremely variable and, to date, no reliable prognostic factors have been validated. Recent literature suggests a primary role of skeletal muscle and its derived signals in ALS progression. To verify this hypothesis, in the present study we evaluated whether ALS is associated with alteration in FDG uptake and total volume of both psoas as a sample of skeletal muscles already used for prognostic stratification in different disorders. Materials and Methods: We analyzed 54 ALS patients with spinal onset consecutively submitted to PET/CT imaging. These data were compared with the corresponding findings in an age-and sex-matched control population. A computational 3D method was used to extract psoas muscle's volumes from CT images and to evaluate total muscle volume and attenuation coefficient. In co-registered PET images, FDG accumulation was defined by average standardized uptake value (a-SUV) and the heterogeneity of its distribution expressed by SUV standard deviation (SUV-SD). Psoas volume was normalized for the ideal body weight. Results: Average psoas attenuation coefficient was similar in patients and controls (39±9 vs 38±11 Housfield units, respectively, ns). By contrast, ALS was associated with a significant reduction in Psoas volume (221±74 mL vs 262±85 mL; p<0.01). This difference persisted when normalization for ideal body weight was considered (3.54±1.02 vs 4.12±1.33 mL/Kg; p<0.05). Similarly, at PET imaging, a-SUV was significantly lower in patients than in controls (0.77±0.21 vs 0.90±0.18; p<0.01). Finally, heterogeneity of psoas a-SUV, expressed by SUV-SD, predicted overall survival rate at Kaplan-Meyer analysis (p<0.05) with a predictive power that was confirmed by univariate as well as by multivariate Cox analysis (p<0.02). Conclusion: ALS is associated with a reduction in volume and FDG uptake of psoas muscles. The heterogeneity of glucose metabolism within this muscular district is related to disease aggressiveness. References: None.