Association of brain structure and motor function in older persons with multiple sclerosis and healthy controls: A cross-sectional study

Abstract

Introduction: Brain structure deteriorates with aging as well as with neurodegenerative diseases such as multiple sclerosis (MS). While these brain changes are accompanied by deterioration of motor function, the association between brain structures and motor function in older people with MS (pwMS) has been scarcely investigated, especially across a broad range of outcomes. Objective: To investigate the association between a broad range of brain structures and motor function outcomes in older pwMS as well as in older, healthy controls (HC). Methods: The present cross-sectional study included n = 41 older pwMS (>= 60 years) and n = 27 age-and sex-matched HC. Assessments included volume and diffusivity of brain structures (evaluated via magnetic resonance imaging) and lower extremity motor function including neuromuscular function (muscle strength evaluated via leg press dynamometry; muscle power via chair rise test) and physical function (walking capacity evaluated via tests of walking speed, endurance, and balance/coordination). Results: Associations between brain volumes and motor function were observed (generally weak, although moderate for lesion load), with more frequent and pronounced associations for walking capacity compared to neuromuscular function. Regarding brain diffusivity, associations were observed (generally weak-to-moderate), again with more frequent and pronounced associations for walking capacity compared to neuromuscular function. Conclusion: Neurodegeneration-specifically the changes in brain volumes and diffusivity-remains a primary driver of motor decline in older pwMS (as well as in age-and sex-matched HC). This appears particularly evident for lesion load and brain diffusivity, being critically linked to various motor outcomes, most notably walking capacity.