Updated MRI Guidelines for Multiple Sclerosis

Newly revised guidelines merge recommendations from the Magnetic Resonance Imaging in Multiple Sclerosis study group, Consortium of Multiple Sclerosis Centres, and North American Imaging in Multiple Sclerosis Cooperative. The guidelines are published in The Lancet Neurology and aim to improve the use of MRI for people with multiple sclerosis (MS). Changes in MRI acquisition protocols emphasize the value of 3 dimensional-fluid-attenuated inversion recovery (3D-FLAIR) as the core brain pulse sequence to improve diagnostic accuracy and identify new lesions or monitor treatment effectiveness. Recommendations for the judicious use of gadolinium-based contrast agents are also provided as is MRI in individuals with multiple sclerosis (MS) during pregnancy, the postpartum period, and childhood.

MRI with field strength of at least 1.5 T and, preferably, 3.0 T is recommended. For 3D imaging, slice thickness of 1 mm isotropic is preferred but, if not available, should not be greater than 1.5 mm with 0.75 mm overlap. For 2D imaging, slices should be no less than 3 mm with no gap, except for diffusion-weighted imaging, which should be at least 5 mm slices with a 10%-30% gap. MRI should cover the whole brain, including as much of cervical cord as possible in the subcallosal plane for 2D imaging or axial oblique for 3D imaging. 

For spinal cord MRI field strength of at least 1.5 T is recommended and 3 T MRI is noted as having no added value compared with 1.5 T. A sagittal slice thickness of at least 3 mm with no gap is recommended and axial slices be at most 5 mm with no gap. Spinal MRI should cover the cervical and thoracolumbar spinal cord, which includes the conus and a perpendicular axial scan orientation to the spinal cord. 

The optic nerve MRI field strength is recommended to be at least 1.5 T and have a sagittal slice thickness of 2 to 3 mm with no gap. There should be coverage for the optic nerve and optic chiasm aligned to the orientation of both.

Specific recommendations for MRI protocols in diagnosis and disease and treatment monitoring are shown in the Table.

For diagnosis, gadolinium-based contrast agents is recommended to show dissemination in time on the baseline MRI scan, contribute to differential diagnosis, predict disease activity, and for phenotyping patients with progressive disease. For disease monitoring, it is recommended that use of gadolinium-based contrast be judiciously used: 
•    In year 1 of follow up if a new baseline MRI was not obtained, especially in those on lower efficacy treatments. 
•    As soon as possible and before steroid treatment in those for whom confirmation of clinical disease activity is needed (when no recent reference MRI is available).To show presence of gadolinium-enhancing lesions if required to initiate or change a specific treatment. 
•    When detection of disease activity is required but difficult to show on the basis of new or enlarged T2 lesions with diffuse and confluent chronic lesions.When lesions on noncontrast MRI are suspicious for progressive multifocal leukoencephalopathy screening 

The new recommendations further simplified and shortened the brain MRI protocol for monitoring purposes, making it easier and more useful than previous guidelines. A new baseline brain MRI scan without gadolinium at least 3 months after treatment initiation and annual noncontrast follow-up scans thereafter is recommended. New to the guidelines is the recommendation to reduce the repeated use of gadolinium-based contrast agents.