Motor fatigue and fatigability in early multiple sclerosis patients: an analysis of clinical, radiological and psychological underpinnings

While fatigue is highly reported in newly diagnosed people with Multiple Sclerosis (pwMS) and motor fatigability is reported in about 20% of non-disabled patients, relationship among them in early MS has been less studied. To evaluate correlations between fatigue and motor fatigability in early pwMS, and their clinical, radiological, psychological underpinnings. Relapsing pwMS aged 18-65 years, Expanded Disability Status Scale (EDSS) score <2.0, disease duration <5 years were recruited. PwMS underwent clinical, cognitive, radiological assessment. They performed a 6-minute-walking-test; fatigability was calculated as the ratio of distance walked in the final minute to the first minute (distance walking index, DWI6−1). Fatigue was evaluated through the Modified Fatigue Impact Scale (MFIS). Spearman ρ examined the relationship among variables; linear regression analyses examined predictors of fatigue and fatigability. 70 pwMS (age 37.8+11years; female n=50, 71.4%, EDSS 1.5[1;2]) were enrolled. 15 (21.4%) reported significant levels of fatigue, 14 (20%) presented motor fatigability. Fatigue and motor fatigability were not significantly correlated with one another (ρ=0.100;p=0.425) or with other clinical, cognitive, radiological features. Fatigue was related to Hospital Anxiety and Depression Scale (HADS) anxiety subscale (ρ=0.375,p=0.002), Beck Depression Inventory (BDI-II) (ρ=0.543;p<0.001), neuroticism (ρ=0.313;p=0.006), and all subscales of MS-Quality-Of-Life 54. We did not find predictors of fatigability, while HADS-anxiety (b=0.76; p=0.003) and BDI-II (b=0.33; p=0.009) significantly predicted fatigue. Our results support different neurobiological underpinnings for motor fatigue and fatigability and reinforce the need for a multidimensional assessment from the earliest stages of the disease, to tailor therapeutic and rehabilitation strategies.