Multiple Sclerosis Severity Scale and whole-brain N-acetylaspartate concentration for patients’ assessment

BACKGROUND—Predicting multiple sclerosis (MS) course is highly desirable but lacking. OBJECTIVE—To test whether the MS Severity Scale (MSSS) and global neuronal viability, assessed through the quantification of the whole-brain N-acetylaspartate concentration, (WBNAA) concur or complement the assessment of individual patient's disease course. METHODS—The MSSS and average WBNAA loss rate (ΔWBNAA, extrapolated based on one current measurement and assumption that at disease onset neural sparing was similar to healthy controls, obtained with proton magnetic resonance (MR) spectroscopy and MRI) from 61 MS patients (18 male and 43 female) with long (15 years or more) disease duration were retrospectively examined. Twenty seven patients exhibited a “benign” disease course, characterized by an Expanded Disease Status Scale score (EDSS) of less than 3.0; and 34 were “non-benign:” EDSS score higher than 3.0. RESULTS—The two cohorts were indistinguishable in age and disease duration. Benign patients' EDSS and MSSS (2.1±0.7, 1.15±0.60) were significantly lower than non-benign (4.6±1.0, 3.6±1.2; both p 0.7). While MSSS is both sensitive to (92.6%) and specific for (97.0%) benign MS, ΔWBNAA is only sensitive (92.6%) but not specific (2.9%). CONCLUSION—Since the WBNAA loss rate is similar in both phenotypes, the only difference between them is their clinical classification, characterized by MSSS and EDSS. This may indicate that “benign” MS probably reflects fortuitous sparing of clinically eloquent brain regions and better utilization of brain plasticity.