Microstructural characterization of the corticospinal tract in stroke patients using advanced diffusion Magnetic Resonance Imaging techniques

Stroke is the leading cause of disability worldwide. Diffusion magnetic resonance imaging (dMRI) is extensively used for performing the diagnosis and prognosis of stroke. Diffusion weighted MRI models are used to accurately characterize the microstructural alterations of brain tissues after stroke. This study aims at assessing the correlation between the structural integrity evolution of white matter brain regions and motor outcome in patients. To investigate these changes, analysis were performed on a set of 15 chronic stroke patients suffering from ischemic and hemorrhagic stroke, and divided into two populations. A total of four MRI data acquisition sessions were conducted between which patient populations followed the HABIT-ILE intensive motor rehabilitation method at different times. Diffusion parameters derived from several microstructural models (DTI, NODDI, DIAMOND, MF) were obtained using the measured MRI scans. The extraction of these diffusion parameters were used for the longitudinal assessment of the microstructural changes in the corticospinal tract (CST), cerebellar peduncles (CP), cortico-ponto cerebellar (CPC) pathway and superior longitudinal fasciculus I (SLF I). The obtained results report contrasted tendencies between both populations as the first population indicated loss of density in WM fibers, loss of myelin sheath integrity and mixing results regarding axonal degeneration whereas the second population showed signs of axonal regrowth, increased fiber density as well as improved myelin sheath integrity. Both populations displayed the majority of their changes in brain WM regions associated with primary motor functions but also showed some variations in secondary motor pathways. These findings reflect the potential but also the limitations of the use of dMRI models in the framework of motor stroke recovery assessment.