Diffusion and perfusion MRI in inflammation and demyelination

In inflammatory and demyelinating disorders of the central nervous system (CNS), conventional MR imaging (MRI) findings are unable to differentiate the heterogeneous pathological substrates of individual lesions, since different tissue changes (i.e., inflammation, demyelination, remyelination, gliosis, and axonal loss) lead to a similar appearance of increased signal intensity on T2-weighted images. Moreover, conventional MRI does not delineate tissue damage occurring beyond T2-visible lesions (i.e., in the normal-appearing white matter [NAWM] and gray matter [GM]).[1,2] Diffusion-weighted MRI (DWI) and perfusion-weighted MRI (PWI) have the potential to improve our understanding of the pathophysiology of inflammatory and demyelinating disorders of the CNS, by overcoming some of these limitations.