Prevalence and patterns of subclinical motor and cognitive impairments in non-disabled individuals with early multiple sclerosis: A multicenter cross-sectional study

Background: Motor and cognitive disorders appear early in the course of multiple sclerosis (MS) and develop gradually over time. Objective: To study the frequency and pattern of subtle functional disorders in people with MS (PwMS) with no overt signs of disability in an early phase of the disease and their association with walking impairments in daily activities. Methods: In this cross-sectional study, we recruited PwMS with an Expanded Disability Status Scale (EDSS) score <= 2.5 and disease duration <= 5 years. Participants were assessed with functional scales rating walking endurance (6-Min Walk Test), perceived walking ability (Twelve-item Multiple Sclerosis Walking Scale), balance (Fullerton Advanced Balance scale_short), manual dexterity (Nine Hole Peg Test), fatigue (Fatigue Severity Scale), and cognitive impairments (Brief International Cognitive Assessment). Results: About 90% of the 82 PwMS (mean [SD] EDSS score 1.5 [0.7] and disease duration 2.2 [1.7] years) showed endurance values below the expected score; almost 30% showed impairment, and for 57%, perceived walking ability score was abnormal. Balance was impaired in 48% of participants, as was manual dexterity (29%) and fatigue (24%), but only a few showed cognitive impairments. Only 11% of PwMS had no abnormal score on the scales used in the assessment. As compared with EDSS score 0 to 1.5, with EDSS score 2 to 2.5, performance was worse for endurance (difference + 61.0 m, P= 0.016), perceived walking ability (-11 points, P = 0.002), balance (+1.9 points, P = 0.005), manual dexterity (-2.8 s, P = 0.004), and fatigue (-1.3 points, P = 0.013). Factors that predicted perceived walking ability were balance (B = -1.37, P < 0.001) and fatigue (B = 5.11, P < 0.001) rather than endurance (B = -0.01, P = 048). Conclusion: Even PwMS with no clinical disability and classified as having "no problem walking" present walking and other functional deficits when assessed with specific functional tests. The addition of specific tools could better identify subtle motor and cognitive deficits. Finally, the assessment of balance disorders and fatigue is important to understand individuals' perceived walking impairments in daily activities. (C) 2021 Elsevier Masson SAS. All rights reserved.