Balance impairment is frequent in Multiple Sclerosis (MS). Attempts to measure balance deficits in clinical practice have mostly relied on EDSS, but its scarce capability to detect subtle deficits is an important limitation.
To compare NIH Toolbox Standing Balance Test (SBT) with EDSS in detecting balance impairment in MS and to assess the contribution of the different Functional Systems (FS) involved in balance on SBT metrics.
128 consecutive MS patients and 36 age and sex-matched healthy controls (HCs) underwent NIH Toolbox SBT at the MS Center of the University of Genoa. Patients underwent clinical evaluation with EDSS FS recording and 3T brain MRI (Siemens Prisma). Theta scores (θ) were derived and corrected for age, sex, height and weight. T2 and T1 lesion volumes (LV) were obtained for the cerebellum and the total brain separately. A linear logistic regression model was performed to evaluate the relative contribution of cerebellar, sensory and brainstem impairment
on balance performance.
92 (73.9%) MS patients were females, mean (SD) age was 41.2 (11.6) years; 108 (84.4%) patients had relapsing-remitting (RRMS) and 20 (15.6%) progressive MS (PMS). Mean disease duration was 10.6 (9.3) years, median (IQR) baseline EDSS was 2.5 (1-4). According to their FS, 73 (53.0%), 57 (44.5%) and 79 (61.7%) patients had no evidence of cerebellar, sensory and brainstem dysfunction respectively. On brain MRI, 95 (74.2%) patients exhibited cerebellar lesions [mean T2LV 0.31 (0.44) mL; mean T1LV 0.20 (0.31) mL]. Patients had significantly lower θ compared with HCs (-0.27vs0.91;p=0.003). RRMS had better performance than PMS patients (-0.05 vs -1.45;p=0.006). Patients with a cerebellar and brainstem FS=0 had higher θ than impaired patients (0.34vs-1.07;p<0.0001 and 0.12vs-0.89;p=0.008 respectively). Patients without impairment in sensory and brainstem FS had worse performance than HCs (0.08vs0.91;p=0.046 and 0.12vs0.91;p=0.048, respectively). Each 1 point increase in cerebellar FS independently determined a -0.50 decrease in θ (95%CI:-0.91-0.09; p=0.017). correlated with cerebellar T2LV and T1LV (Spearman r-0.29,p=0.001 and r=-0.28,p=0.001 respectively) but not with global T2LV and T1LV.
NIH Toolbox SBT is able to detect subtle balance impairment in MS patients, not detected by clinical examination. Clinical and radiological cerebellar involvement seem to be specifically related to NIH Toolbox SBT metric.