Time course of lesion-induced atrophy in multiple sclerosis.

BACKGROUND AND PURPOSE: White matter (WM) tract disruption impacts volume loss in connected deep gray matter (DGM) over 5 years in people with multiple sclerosis (PwMS). However, the timeline of this phenomenon remains poorly characterized. MATERIALS AND METHODS: Annual serial MRI for 181 PwMS was retrospectively analyzed from a 10-year clinical trial database. Annualized thalamic atrophy, DGM atrophy, and disruption of connected WM tracts were measured. For time series analysis, ~700 epochs were collated using a sliding 5-year window, and regression models predicting 1-year atrophy were applied to characterize the influence of new tract disruption from preceding years, while controlling for whole brain atrophy and other relevant factors. RESULTS: Disruptions of WM tracts connected to the thalamus were significantly associated with thalamic atrophy 1 year later (ß: 0.048-0.103). This effect was not observed for thalamic tract disruption concurrent with the time of atrophy nor for thalamic tract disruption preceding the atrophy by 2-4 years. Similarly, disruptions of white matter tracts connected to the DGM were significantly associated with DGM atrophy 1 year later (ß: 0.078-0.111), but not for tract disruption concurrent with, nor preceding the atrophy by 2-4 years. CONCLUSION: Increased rates of thalamic and DGM atrophy were restricted to 1 year following newly developed disruption in connected WM tracts. In research and clinical settings, additional gray matter atrophy may be expected 1 year following new lesion growth in connected white matter.

Lower self-report fatigue in multiple sclerosis is associated with localized white matter tract disruption between amygdala, temporal pole, insula, and other connected structures.

BACKGROUND: Fatigue, a frequent and disabling symptom for people with multiple sclerosis (PwMS), inconsistently correlates with white matter (WM) pathology. Network-based analysis, accounting for the manner in which lesions disrupt networks of structurally connected gray matter (GM) regions, may provide additional insight. OBJECTIVE: To identify patterns of WM tract disruption which explain self-reported fatigue severity in PwMS. METHODS: 137 PwMS and 50 age- and sex-matched healthy controls (HC) underwent fatigue assessment and brain MRI. Lesion maps were applied to determine the severity of WM tract disruption between pairs of GM regions. Then, the Network-Based-Statistics tool was applied to identify structural networks whose disruption explained fatigue severity. To determine whether these networks explain unique variance above conventional MRI measures and depression, regressions were applied controlling for age, sex, brain volume, T2-lesion volume, and depression. RESULTS: Patient-perceived fatigue in PwMS was positively associated with overall lesion burden (ß = 0.563, p-value < 0.001). In contrast, localized disruptions in WM tracts between regions including the amygdala, insula, hippocampus, putamen, temporal pole, caudal-middle-frontal gyrus, rostral-middle-frontal gyrus, inferior-parietal gyrus, and banks of the superior temporal sulcus were significantly negatively correlated with fatigue in PwMS (ß = -0.586, p-value < 0.001). Average disruption within this specific, localized network explained significant additional variance in fatigue above what was otherwise explained by depression and conventional MRI measures of neuropathology (ΔR2 = 0.078, p-value < 0.001). CONCLUSION: Although overall lesion burden correlates positively with fatigue in PwMS, localized WM damage between the amygdala, temporal pole, and other connected structures is associated with lower severity of patient-perceived fatigue.

White matter tract network disruption explains reduced conscientiousness in multiple sclerosis.

Quantifying white matter (WM) tract disruption in people with multiple sclerosis (PwMS) provides a novel means for investigating the relationship between defective network connectivity and clinical markers. PwMS exhibit perturbations in personality, where decreased Conscientiousness is particularly prominent. This trait deficit influences disease trajectory and functional outcomes such as work capacity. We aimed to identify patterns of WM tract disruption related to decreased Conscientiousness in PwMS. Personality assessment and brain MRI were obtained in 133 PwMS and 49 age- and sex-matched healthy controls (HC). Lesion maps were applied to determine the severity of WM tract disruption between pairs of gray matter regions. Next, the Network-Based-Statistics tool was applied to identify structural networks whose disruption negatively correlates with Conscientiousness. Finally, to determine whether these networks explain unique variance above conventional MRI measures and cognition, regression models were applied controlling for age, sex, brain volume, T2-lesion volume, and cognition. Relative to HCs, PwMS exhibited lower Conscientiousness and slowed cognitive processing speed (p = .025, p = .006). Lower Conscientiousness in PwMS was significantly associated with WM tract disruption between frontal, frontal-parietal, and frontal-cingulate pathways in the left (p = .02) and right (p = .01) hemisphere. The mean disruption of these pathways explained unique additive variance in Conscientiousness, after accounting for conventional MRI markers of pathology and cognition (ΔR2  = .049, p = .029). Damage to WM tracts between frontal, frontal-parietal, and frontal-cingulate cortical regions is significantly correlated with reduced Conscientiousness in PwMS. Tract disruption within these networks explains decreased Conscientiousness observed in PwMS as compared with HCs.