What is the role of MRI in the diagnosis and follow-up of multiple sclerosis (MS)?

Updated: Mar 27, 2019
  • Author: James A Wilson, MD, MSc, FRCPC; Chief Editor: James G Smirniotopoulos, MD  more...
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Answer

The advent of MRI has revolutionized the diagnosis and monitoring of MS. MRI is well established as the preferred imaging modality for depicting MS lesions. In patients with clinically definite MS (CDMS), MRI demonstrates a high rate of abnormal findings compatible with the diagnosis. In a study by Lukes et al, lesions were demonstrated in 10 patients with CDMS. [23] In a larger study by Robertson et al, MRI findings were abnormal in 124 of 133 patients with CDMS. Ormerod et al found that 112 of 114 patients with CDMS had abnormal MRI findings and that 102 of 114 had discrete white matter lesions. [24]

Another major use of MRI has been the evaluation of patients who have had only 1 episode of neurologic impairment and who do not meet the clinical criteria for the diagnosis. The overall risk of developing MS after a single episode of neurologic impairment is estimated to be as low as 12% (2-yr follow-up study by Beck et al) to as high as 45% (12.9-yr follow-up study by Sandberg-Wollheim et al [25] ) or 58% (14.9-yr follow-up study by Rizzo et al [26] ).

MRI has been proven to be the most useful investigation for predicting the progression to MS. In a 10-year follow-up study of patients with a clinically isolated event, 45 (83%) of 54 patients with abnormal MRI findings went on to develop clinical MS, whereas only 3 of 27 with normal MRI findings developed MS. [27]

Tintoré et al followed up 70 patients for an average of 28.3 months after an isolated neurologic event and compared various MRI criteria for the diagnosis MS, as defined by Paty et al, Fazekas et al, and Barkhof et al. [4, 5, 28, 29] With the method of Paty et al, which requires 3 or 4 lesions (1 of which is periventricular), the authors reported a sensitivity of 86% but a specificity of only 54%. The criteria of Fazekas et al resulted in the same sensitivity and specificity. These criteria require 3 lesions with 2 of the 3 following characteristics: infratentorial location, periventricular location, and lesion greater than 6 mm. The criteria of Barkhof require 1 infratentorial lesion, 1 juxtacortical lesion, 3 periventricular lesions, and either 1 gadolinium-enhanced lesion or more than 9 lesions on T2-weighted MRI scans. These criteria resulted in a sensitivity of 73% and a specificity of 73%. Thus, as the MRI criteria become more stringent in the diagnosis of MS, specificity increases at the expense of decreasing sensitivity.

In a cohort of the BENEFIT study (a multicenter, randomized, clinical study of 468 patients), the modified Barkhof criteria showed moderate predictive value for conversion to CDMS over 3 years, despite the fact that all patients received interferon beta-1b therapy for at least 1 year. Follow-up MRI was found to be most informative after 9 months in patients without dissemination in space at baseline. The overall conversion rate to CDMS was 42%. Barkhof criteria with the strongest prognostic value were the presence at baseline of at least 9 T2-weighted lesions and at least 3 periventricular lesions. [30]

According to a study of postmortem MS tissue by Pitt et al, 3-dimensional (3-D), T2*-weighted, gradient-echo (T2*GRE) and white matter–attenuated, turbo-field-echo (TFE) sequences at a 7T field strength can detect most cortical lesions. The 3-D T2*GRE and white matter–attenuated TFE sequences retrospectively detected 93% and 82% of all cortical lesions, respectively. [31]

Susceptibility MRI contrast variations reflect alterations in brain iron and myelin content. In 24 MS patients (306 white matter lesions) who underwent 7T MRI of the brain, most lesions were hypointense on R2*. Hyperintense lesions on quantitative susceptibility mapping were more frequent in relapsing-remitting MS than in progressive MS. Hyperintense lesion rims on quantitative susceptibility maps were more common in progressive MS and in patients with higher levels of disability and fatigue. Mean lesion R2* was inversely related to disability and fatigue and significantly reduced in progressive MS. Relative susceptibility was lower in lesions in progressive MS than in relapsing-remitting MS. [32]


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