Evidence for gray matter pathology in multiple sclerosis: a neuroimaging approach

The purpose of this special issue is to synthesize current concepts about the pathogenesis, MRI measurements and clinical relevance of gray matter (GM) pathology in patients with multiple sclerosis (MS). Progressive GM pathology in MS has been recognized for a long time, however, only in recent years has detection of cortical GM lesions by specific pathology techniques uncovered the full extent of GM damage in MS. This issue reviews current knowledge about GM pathology, as assessed by neuroimaging techniques in early and chronic MS. Some new concepts are discussed with respect to how venous hemodynamic alterations may play an important role in the pathophysiology of MS. The issue emphasizes the critical need for development of better neuroimaging tools that can be used for in vivo visualization of GM pathology in patients with MS. Measures described include specific regional atrophy, diffusion tensor imaging, magnetic resonance spectroscopy, and magnetization transfer imaging, as well as optic nerve imaging techniques. Under development are promising new MRI sequences and analyses that will better identify and characterize cortical lesions. GM pathology imaging correlates are related to disability progression, as measured both by motor and cognitive functional outcomes.