What is the role of MRI in the workup of neurosarcoidosis?

Updated: Nov 13, 2018
  • Author: Gabriel Bucurescu, MD, MS; Chief Editor: Tarakad S Ramachandran, MBBS, MBA, MPH, FAAN, FACP, FAHA, FRCP, FRCPC, FRS, LRCP, MRCP, MRCS  more...
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Answer

MRI scans of the brain and spine are indispensable in assessing nervous system involvement. Imaging studies of specific regions or organ systems may be appropriate if clinically indicated or if laboratory testing suggests involvement of that organ system. Although computed tomography may also be used, MRI has become the modality of choice because of the superior images obtained.

The use of gadolinium and fluid-attenuated inversion recovery (FLAIR) has increased the sensitivity of an MRI, helping identify T2 enhancement of nerve roots, plexuses, and limb nerves. MRI of peripheral nerves may occasionally show a diffusely enlarged nerve as a soft tissue mass.

Some series have shown that gadolinium enhancement demonstrated leptomeningeal involvement in cases that unenhanced images might have missed. The enhancement can follow the contour of the brain, extending into the cortical sulci. Gadolinium also can leak into the contiguous CSF because of disruption of capillary endothelial tight junctions of the arachnoid matter.

A thick and ragged pial enhancement is indicative of invasion along perivascular spaces, leading to a meningoencephalovasculopathy. Enhancement of linear and nodular areas from the pial surface into the white matter indicates infiltration along Virchow-Robin spaces.

In the FLAIR technique, the signal from the CSF is suppressed, and mild or heavy T2 weighting (long TE) is used to detect lesions. This technique is of value in detecting low-contrast lesions. It also can be used to improve the accuracy of detecting T2 prolongation in the temporal lobe in cases of mesial temporal sclerosis.

The nulling of the CSF signal maximizes the sensitivity of the sequence to changes in the T1 of the CSF. The FLAIR technique is valuable in diffusion weighting and is especially sensitive to contrast enhancement. It also can be combined with fat suppression.


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