June 15, 2021 – Alicia Bigica
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New consensus guidelines update clinical practice and point to a unified, worldwide approach to multiple sclerosis diagnosis and monitoring.
This article first appeared on Diagnostic Imaging’s sister site, NeurologyLive.
Providers worldwide now have new MRI guidelines for imaging patients with multiple sclerosis that incorporate both new safety data and recent imaging improvements.
For the first time, experts in multiple sclerosis (MS) from North America and Europe have aligned on consensus recommendations for the use of MRI in people with MS. These guidelines—developed by the Magnetic Resonance Imaging in Multiple Sclerosis (MAGNIMS) study group; the Consortium of Multiple Sclerosis Centers (CMSC) working group; and the North America Imaging in Multiple Sclerosis (NAIMS) MRI Guidelines working group—address these developments, as well as other clinical updates.
A main focus and key update included in the recommendations is the use of standardized MRI protocols for both diagnostic and prognostic purposes, the importance of which was emphasized in the 2017 updates to the McDonald criteria. Previous guidelines from MAGNIMS and CMSC issued in 2015 and 2016, respectively, recommended the use of axial single T2-weighted sequences, dual echo T2-weighted spin echo sequences, axial and sagittal T2-weighted fluid-attenuated inversion recovery (FLAIR), and contrast enhanced axial T1-weighted sequences, preferably at 3 Tesla (T). While these recommendations are still in line with the current McDonald criteria, the new recommendations emphasize the use of 3D acquisition techniques, especially for FLAIR and T1-weighted sequences, as they can both improve lesion detection and contribute to better realignment of anatomic orientation on serial scans.
While the groups recommend sagittal 3D FLAIR acquisition to be the core sequence used for both diagnosis and monitoring of MS, high quality 2D pulse-sequences, with less than or equal to 3 mm slice thickness and no gap between slices, is an acceptable alternative. Although 3T scanners offer optimal lesion detection and acquisition times, 1.5T scanners are sufficient; those with a strength less than 1.5T are not recommended. Notably, the groups do not recommend the use of 7T scanners at this time, reserving their use for research purposes.
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Pointing out the high value of spinal cord MRI to show dissemination in time and space and for exclusion of other diagnoses, the groups recommend that the standard MS imaging protocol must include at least 2 of the following 3 sagittal sequences: T2-weighted spin echo with moderately long echo times, proton density-weighted echo, or short tau inversion recovery (STIR). If contrast agents are used, a T1-weighted spin echo sequence should be included, as well.
In light of new safety advisories from both the US FDA and European Medicines Agency regarding the accumulation of gadolinium-based contrast agents (GBCAs) in the brain, the recommendations support the continued use of single-dose GBCA—but not double- or triple-dose—with special considerations for time delay between GBCA administration and T1-weighted acquisition (ideally 10 minutes) during initial and subsequent scans.
Emerging Biomarkers
Several new imaging biomarkers of MS have begun to emerge in the literature, most notably the central vein sign. While valuable for distinguishing MS from mimics, the groups do not currently recommend use of the central vein sign in routine clinical use as the pulse sequences needed for detection are not widely available on clinical scanners and it requires expert image interpretation. Similarly, paramagnetic rim lesions and leptomeningeal inflammation are not currently recommended as more time is needed to validate these as imaging biomarkers.
MRI for Treatment Effectiveness and Disease Monitoring
After obtaining a baseline MRI (with or without GBCA), the groups recommend a new brain MRI without GBCAs 3 to 6 months after starting treatment or switching disease-modifying therapy (DMT). Annual brain MRI should continue while on DMT, and longer intervals are acceptable for those who are clinically stable or don’t require safety monitoring after several years of treatment. Brain MRI should be performed in an identical manner at each follow-up according to the above-mentioned protocol, while spinal cord and optic nerve MRI are not routinely recommended unless in clinical situations that require them. New or enlarging T2 lesions should be reported, as well as recognition of poor sensitivity for cortical grey matter lesions and use of co-registration, fusion, and subtraction tool techniques. Notably, volumetric and quantitative MRI measures are not routinely recommended.
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