Abstract and Introduction
This review will address the critical role of radiographic techniques in monitoring multiple sclerosis disease course and response to therapeutic interventions using conventional imaging. We propose an algorithm of obtaining a contrast-enhanced brain MRI 6 months after starting a disease-modifying therapy, and considering a gadolinium-enhancing lesion on that scan to indicate suboptimal response to therapy. New or enlarging T2 lesions should be followed on scans at 6-month intervals to assess for change, and the presence of one or more enhancing lesions on a 6- or 12-month scan, or two or more new or enlarging T2 lesions on a 12-month scan should prompt consideration of therapy change. New techniques such as PET imaging, magnetic resonance spectroscopy, magnetic resonance relaxometry, iron-sensitive imaging and perfusion MRI will also be overviewed, with their potential roles in monitoring disease course and activity.
Recent updates to the MRI diagnostic criteria for multiple sclerosis (MS) have simplified the guidelines and allowed for earlier diagnosis with preserved diagnostic sensitivity and specificity. CNS lesions disseminated in space and time remain the two key features of the diagnosis, and the latter can be established with a single scan in a patient with a clinically silent gadolinium (GAD)-enhancing lesion and another clinically silent T2 lesion. Alternatively, any new T2 lesion after an original scan can define dissemination in time. Dissemination in space may be satisfied by at least one T2 lesion in two of the following four characteristic areas for MS: periventricular, juxtacortical, infratentorial and spinal cord. These 2010 criteria make diagnosis of relapsing–remitting MS (RRMS) more straightforward compared with a prior version of the McDonald criteria, revised in 2005.
While MRI metrics as described above have been critically important in MS diagnostic criteria, in this review we will focus on the importance of white matter lesions in clinical decision-making, specifically in determining suboptimal response to therapy. Several advanced imaging techniques have potential importance in diagnosing MS and following progression and response to treatment. These include methods of imaging gray matter in MS patients, in addition to normal-appearing white matter and quantification of brain atrophy. We will discuss these methods, as well as potential applications of myelin and iron-sensitive imaging and other advanced imaging techniques that hold promise for furthering the understanding of MS. We recognize, however, that at this time the mainstay of imaging in MS is focused on lesions and conventional techniques.
Expert Rev Neurother. 2012;12(3):323-333. © 2012 Expert Reviews Ltd.