Multiple sclerosis update: use of MRI for early diagnosis, disease monitoring and assessment of treatment related complications

Abstract

MRI has long been established as the most sensitive in vivo technique for detecting multiple sclerosis (MS) lesions. The 2010 revisions of the McDonald Criteria have simplified imaging criteria, such that a diagnosis of MS can be made on a single contrast-enhanced MRI scan in the appropriate clinical context. New disease-modifying therapies have proven effective in reducing relapse rate and severity. Several of these therapies, most particularly natalizumab, but also dimethyl fumarate and fingolimod, have been associated with progressive multifocal leukoencephalopathy (PML). PML-immune reconstitution inflammatory syndrome (IRIS) has been recognized in patients following cessation of natalizumab owing to PML, and discontinuation for other reasons can lead to the phenomenon of rebound MS. These complications often provide a diagnostic dilemma and have implications for imaging surveillance of patients. We demonstrate how the updated McDonald Criteria aid the diagnosis of MS and describe the imaging characteristics of conditions such as PML and PML-IRIS in the context of MS. Potential imaging surveillance protocols are considered for the diagnosis and assessment of complications. We will explain how changes in MS treatment are leading to new imaging demands in order to monitor patients for disease progression and treatment-related complications.

Figure 1.

A 29-year-old male presented with a 2-week history of right leg numbness, right hand weakness and brisk reflexes bilaterally with sustained clonus. T₂ weighted and fluid-attenuated inversion recovery imaging show multiple hyperintensityies. A posterior left frontal lobe lesion (arrows) shows enhancement following contrast administration. An anterior right frontal lobe lesion does not (dashed arrows). This single study demonstrates both dissemination in space and dissemination in time.

Figure 2.

A patient with known multiple sclerosis (MS) on treatment with natalizumab presented with progressive changes in behaviour. Coronal fluid-attenuated inversion recovery (FLAIR) imaging (a, b) shows an ill-defined focus of high signal within the medial left frontal lobe (solid arrows), without restricted diffusion on diffusion-weighted imaging/apparent diffusion coefficient (c, d). A repeat MRI scan performed 6 weeks later shows enlargement of the pre-existing left frontal lobe lesion (e and f, solid arrows). There is also faint punctate contrast enhancement at the posterior aspect of the lesion (h, dashed line). A new ill-defined high T₂/FLAIR lesion is also now seen within the left temporal lobe (f, dotted line). Findings are consistent with progressive multifocal leukoencephalopathy. Pre-existing MS lesions within both centrum semiovale are noted.

Figure 3.

Axial fluid-attenuated inversion recovery (a, b) and contrast-enhanced T₁ weighed images (c, d) of a 54-year-old patient with patients with relapsing-remitting multiple sclerosis being treated with natalizumab longer than 3 years at the time of progressive multifocal leukoencephalopathy (PML) diagnosis (a, c) and at the time of PML- immune reconstitution inflammatory syndrome (IRIS) (b, d). The PML lesion at the time of the diagnosis shows typical PML lesion characteristics without any mass effect or perilesional oedema (closed head arrows). At the PML-IRIS stage, the immune reconstitution causes substantial inflammation leading to multifocal contrast enhancement inside and outside of the main PML lesion (d, open head arrows) and swelling, mass effect and perilesional oedema (c, open head arrows).