Abstract
ObjectiveTo characterize microstructural white matter changes related to relapsing-remitting multiple sclerosis using advanced diffusion MRI modeling and tractography. The association between imaging data and patient’s cognitive performance, fatigue severity and depressive symptoms is also explored.MethodsIn this cross-sectional study, 24 relapsing-remitting multiple sclerosis patients and 11 healthy controls were compared using high angular resolution diffusion imaging (HARDI). The imaging method includes a multi-shell scheme, free water correction to obtain tissue-specific measurements, probabilistic tracking algorithm robust to crossing fibers and white matter lesions, automatic streamlines and bundle dissection and tract-profiling with tractometry. The neuropsychological evaluation included the Symbol Digit Modalities Test, Paced Auditory Serial Addition Test, Modified Fatigue Impact Scale and Beck Depression Inventory-II.ResultsBundle-wise analysis by tractometry revealed a difference between patients and controls for 11 of the 14 preselected white matter bundles. In patients, free water corrected fractional anisotropy was significantly reduced while radial and mean diffusivities were increased, consistent with diffuse demyelination. The fornix and left inferior fronto-occipital fasciculus exhibited a higher free water fraction. Eight bundles showed an increase in total apparent fiber density and four bundles had a higher number of fiber orientations, suggesting axonal swelling and increased organization complexity, respectively. In the association study, depressive symptoms were associated with diffusion abnormalities in the right superior longitudinal fasciculus.ConclusionTissue-specific diffusion measures showed abnormalities along multiple cerebral white matter bundles in patients with relapsing-remitting multiple sclerosis. The proposed methodology combines free-water imaging, advanced bundle dissection and tractometry, which is a novel approach to investigate cerebral pathology in multiple sclerosis. It opens a new window of use for HARDI-derived measures and free water corrected diffusion measures. Advanced diffusion MRI provides a better insight into cerebral white matter changes in relapsing-remitting multiple sclerosis, namely diffuse demyelination, edema and increased fiber density and complexity.
Highlights
Multiple sclerosis (MS) is a neurodegenerative disease of the central nervous system characterized by chronic inflammation, demyelination, axonal degeneration, and gliosis (Compston and Coles, 2008)
All statistical tests were performed with IBM SPSS Statistics 25 (SPSS Inc., Chicago, Illinois)
For each diffusion MRI measure (FAt, RDt, MDt, free water fraction, AFDtot, number of fiber orientation (NuFO)), the difference between relapsing-remitting multiple sclerosis (RRMS) patients and healthy controls was investigated with the appropriate parametric and non-parametric (Mann–Whitney test) tests
Summary
Multiple sclerosis (MS) is a neurodegenerative disease of the central nervous system characterized by chronic inflammation, demyelination, axonal degeneration, and gliosis (Compston and Coles, 2008). In addition to various physical signs and symptoms, affected individuals present variable degrees of cognitive impairment, which has a prevalence ranging from 40 to 70% in MS patients (Amato et al, 2006; Chiaravalloti and DeLuca, 2008; Langdon, 2011). Information processing speed, episodic memory and executive functions are frequently affected cognitive domains, even early in the disease (Rocca et al, 2015; Johnen et al, 2017). Comorbid depression (Feinstein, 2011) and fatigue (Chiaravalloti and DeLuca, 2008) are highly prevalent in patients with MS. The underlying cause of MS-related fatigue is still poorly understood but it is thought to have a central origin (Filippi et al, 2002; DeLuca et al, 2008)
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