Structural and cognitive correlates of fatigue in progressive multiple sclerosis

Fatigue in multiple sclerosis (MS) is a debilitating symptom and experienced by most patients. In recent studies investigating this phenomenon, the majority of patients had a relapsing-remitting disease course.

Patients with progressive MS participating in one of three treatment trials during a period from 2010 to 2014 were included. Fatigue was assessed with the Fatigue Scale for Motor and Cognitive Functions (FSMC) and patients were further examined with a cognitive test battery, including Symbol Digit Modalities Test (SDMT), and 3 T MRI with subsequent quantitative analyses of 13 cortical regions of interest, deep grey matter and lesion volume.

Twenty-two patients were enrolled. The thickness of the pre-central gyrus correlated significantly with motor fatigue. We found only a non-significant trend towards a correlation between cognitive fatigue and the thickness of the pre-central gyrus, the parietal inferior supra-marginal gyrus and the opercular part of the inferior frontal gyrus. 36% of participants had impaired processing speed and 9% had normal function on all tests. The scores on the FSMC-cognitive scale were related to performance on SDMT.

In this exploratory study of patients with progressive MS, fatigue was related to processing speed. Motor fatigue was also related to the cortical thickness of the primary motor cortex and there was a trend towards a relationship between cognitive fatigue and the thickness of cortical areas involved in attentional processes. Additional studies are needed to further elucidate the relationship between regional cortical atrophy, cognitive functioning and the perception of fatigue.

FSMC: Motor and Cognitive Functions; MS: Multiple Sclerosis; SDMT: Symbol Digit Modalities Test; MRI: Magnetic Resonance Imaging; RRMS: Relapsing-Remitting Disease Course; EDSS: Kurtzke Expanded Disability Status Scale; FLAIR: Fluid Attenuated Inversion Recovery; NAWM: Normal-Appearing White Matter; CGM: Cortical Grey Matter; CTh: Cortical Thickness; ROIs: Regions of Interest; Raven: Raven Progressive Matrices; TM A: Trail Making A; TM B: Trail Making B; Rey: Rey Complex Figure; Similarities: WAIS III Similarities; Stroop: Stroop Colour Naming Test; BDI: Becks Depression Inventory II.