word count: 250 Text word count: 2894 2 ABSTRACT Purpose: The disease course of multiple sclerosis (MS) is unpredictable and reliable prognostic biomarkers are needed. Positron emission tomography (PET) with β-amyloidtracers is a promising tool to evaluate white matter (WM) damage and repair. Our aims were to investigate amyloid uptake in damaged (DWM) and normal-appearing WM (NAWM) of MS patients, and to evaluate possible correlations between cerebrospinal fluid (CSF) β-Amyloid1-42 (Aβ) levels, amyloid tracer uptake and brain volumes.Methods: Twelve MS patients were recruited and divided according to their disease activity into active and non-active groups. All participants underwent neurological examination, neuropsychological testing, lumbar puncture, brain magnetic resonance (MRI) imaging, and 18 F-florbetapir PET. Aβ levels were determined in CSF samples from all patients. MRI and PET images were co-registered and mean standardized uptake values (SUV) were calculated for each patient in the NAWM and in the DWM. To calculate brain volumes, brain segmentation with statistical parametric mapping software was performed. Non-parametric statistical analyses for between-group comparisons and regression analyses were conducted.
Results:We found a lower SUV in DWM compared to NAWM (p<0.001) in all patients.A decreased NAWM-SUV in active compared to non-active group was observed (p<0.05). Considering only active patients, NAWM volume correlated with NAWM-SUV (p=0.01). Interestingly, CSF Aβ concentration was a predictor of both NAWM-SUV (r=0.79; p=0.01) and NAWM volume (r=0.81, p=0.01).
Conclusions:The correlation between CSF Aβ levels and NAWM-SUV suggests that the predictive role of β-amyloid may be linked to myelin early damage and may reflect the disease activity and the clinical progression.