Early Upper Limb Motor Impairment in Multiple Sclerosis Across EDSS Levels: A Case–Control Study

BACKGROUND: Upper limb (UL) involvement is common from the early stages in people with multiple sclerosis (PwMS) and has a significant impact on daily activities, quality of life, and autonomy. However, it may be underestimated by the Expanded Disability Status Scale (EDSS). AIM: The objective of this study was to determine differences in UL function between PwMS, stratified by EDSS ≤3.5 and >3.5, and healthy controls (HCs), as well as between PwMS subgroups according to EDSS score. METHODS: A case-control study was conducted following STROBE guidelines. Participants with MS were stratified into two groups on the basis of disease severity (EDSS ≤3.5 and >3.5). UL function was assessed using the hand grip strength (HGS) test, Box and Block Test (BBT), Nine-Hole Peg Test (NHPT), and ABILHAND questionnaire. Additionally, fatigue and disease impact were evaluated using the Fatigue Severity Scale (FSS) and the Multiple Sclerosis Impact Scale 29 (MSIS-29). HCs were assessed using the HGS test, BBT, and NHPT. RESULTS: PwMS (n = 69; median age 49 years [interquartile range-IQR 13]; 66.7% female; 34 relapsing-remitting MS, 21 secondary progressive MS, and 14 primary progressive MS; median EDSS 6.0 [IQR 2.5]) showed significant impairments in all objective UL measures compared with HC (n = 23; median age 44.5 years [IQR 32]; 56.5% female), even at low levels of neurological disability. Differences between EDSS subgroups were observed in BBT and NHPT for the more affected UL, whereas no significant difference was found for the HGS test. For the less affected UL, only NHPT differed significantly between EDSS subgroups. No statistically significant differences were found between EDSS subgroups for ABILHAND, FSS, or MSIS-29. CONCLUSIONS: These findings suggest that EDSS alone may not adequately capture UL dysfunction. The use of objective, sensitive, and validated assessments is essential to detect UL deficits, including subtle impairments, from early stages of MS, supporting the need for a multidimensional approach to UL disability assessment.