Neuroimaging in multiple sclerosis

Abstract

Magnetic Resonance Imaging (MRI) is the principal neuroimaging technique applied to Multiple Sclerosis (MS). Since the early 1990s, conventional MRI (c-MRI) has become a fundamental tool for MS diagnosis, management and research (Miller DH, Grossman RI, Reingold SC, McFarland HF (1998) The role of magnetic resonance techniques in understanding and managing multiple sclerosis. Brain 1(121):3-24). The distinctive features of c-MRI are its high sensitivity to focal white matter (WM) lesions as well as to infraclinical disease activity which is characterized by the appearance of new lesions in the absence of signs and/or symptoms of clinical relapse. In acknowledging these properties, MS diagnostic criteria have implemented specific c-MRI criteria, so that this technique has been chosen as the main paraclinical tool for supporting and reaching MS diagnosis (McDonald WI, Compston A, Edan G, et al (2001) Recommended diagnostic criteria for multiple sclerosis: guidelines from the international panel on the diagnosis of multiple sclerosis. Ann Neurol 50:121-127; Polman CH, Reingold SC, Edan G, et al (2005) Diagnostic criteria for multiple sclerosis: 2005 revisions to the McDonald Criteria. Ann Neurol 58:840-846; Polman CH, Reingold SC, Banwell B, et al (2011) Diagnostic criteria for multiple sclerosis: 2010 revisions to the McDonald criteria. Ann Neurol 69(2):292-302). More recently, non-conventional MRI (nc-MRI) techniques have allowed researchers to investigate in vivo the pathophysiology of MS. These techniques have been able to confirm, or even anticipate, results of neuropathological studies showing the presence of diffuse microscopic damage outside focal WM lesions, including normal-appearing WM (NAWM) and gray matter (GM). nc-MRI-derived metrics have also prompted considerable interest since it has been shown that they correlate better with clinical disability scores than those deriving from c-MRI-derived. Finally, functional MRI (fMRI), the most recent and advanced nc-MRI technique, has made it possible to investigate mechanisms of cortical neuroplasticity in MS, reporting very promising results.