Association of daily physical activity with brain volumes and cervical spinal cord areas in multiple sclerosis.

BACKGROUND: Remote activity monitoring has the potential to evaluate real-world, motor function, and disability at home. The relationships of daily physical activity with spinal cord white matter and gray matter (GM) areas, multiple sclerosis (MS) disability and leg function, are unknown. OBJECTIVE: Evaluate the association of structural central nervous system pathology with ambulatory disability. METHODS: Fifty adults with progressive or relapsing MS with motor disability who could walk >2 minutes were assessed using clinician-evaluated, patient-reported outcomes, and quantitative brain and spinal cord magnetic resonance imaging (MRI) measures. Fitbit Flex2, worn on the non-dominant wrist, remotely assessed activity over 30 days. Univariate and multivariate analyses were performed to assess correlations between physical activity and other disability metrics. RESULTS: Mean age was 53.3 years and median Expanded Disability Status Scale (EDSS) was 4.0. Average daily step counts (STEPS) were highly correlated with EDSS and walking measures. Greater STEPS were significantly correlated with greater C2-C3 spinal cord GM areas (ρ = 0.39, p = 0.04), total cord area (TCA; ρ = 0.35, p = 0.04), and cortical GM volume (ρ = 0.32, p = 0.04). CONCLUSION: These results provide preliminary evidence that spinal cord GM area is a neuroanatomical substrate associated with STEPS. STEPS could serve as a proxy to alert clinicians and researchers to possible changes in structural nervous system pathology.

A simplified approach to define cervical vertebral levels in spinal cord MRI studies.

BACKGROUND AND PURPOSE: Spinal cord (SC) cross-sectional areas (CSAs) assessed with MRI have proven to be extremely valuable imaging markers in several diseases. Among the challenges is the delineation of vertebral levels to determine level-dependent changes in cord atrophy. With this study, we aimed to (1) test the hypothesis that there is proportionality in the position of the first six intervertebral discs and the length of the upper portion of the SC and (2) show that a proportionality approach can simplify the CSA assessment across vertebrae offering good reliability. METHODS: Forty-six volunteers underwent standard T2-weighted and T1-weighted cervical SC MRI acquisitions. The distance between the obex and the intervertebral discs (from C2-C3 to T1-T2) was measured on the T2-weighted acquisitions of the entire cohort. In a test-retest experiment on 12 subjects, the % disc position values were used to define vertebral levels, and a comparison was performed with manual vertebrae assignment in terms of mean CSA and its coefficient of variation. RESULTS: The mean upper cord length for the cohort was 144.0 ± 13.1 mm. The discs' level % position in the upper cord was found to be fairly consistent, with standard deviations of 0.8%-1.7%. The mean vertebral CSA obtained with the proportionality method was substantially equivalent to the manual approach in terms of mean CSA values and test-retest reliability. CONCLUSIONS: With this study, we propose a proportionality method for the assignment of cervical SC vertebral levels that can simplify the processing of MRI datasets in the context of CSA measurements.