What is the role of FLAIR MRI in the diagnosis 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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Newer MRI pulse sequences and techniques, including fluid-attenuated inversion recovery (FLAIR) MRI and MR spectroscopy, have emerged that are potentially useful in the evaluation of patients with MS.

FLAIR MRI is a heavily T2-weighted technique that dampens the ventricular (ie, free-water) CSF signal. Thus, the highest signals on the sequence are from certain brain parenchymal abnormalities, such as MS lesions, while the CSF appears black. This appearance is different from that on PD-weighted MRIs, on which periventricular MS lesions may appear nearly isointense to the adjacent CSF.

MTR-based imaging or multi-compartment diffusion imaging might be useful to investigate the effect of drugs promoting remyelination, while post-contrast FLAIR could be applied to investigate the monitoring response to drugs targeting B cells. [39]

(See the image below.)

Coronal fluid-attenuated inversion recovery (FLAIR Coronal fluid-attenuated inversion recovery (FLAIR) MRI in a patient with multiple sclerosis demonstrates periventricular high–signal intensity lesions, which exhibit a typical distribution for multiple sclerosis. FLAIR MRI is a highly sensitive sequence for lesion detection, particularly supratentorially.

The greater relative suppression of CSF on FLAIR images compared with PD-weighted series increases the contrast between periventricular lesions and CSF, enhancing their detection. FLAIR has been shown to be superior to PD-weighted sequences in the detection of MS lesions in the cerebral hemispheres. However, PD-weighted imaging remains the investigation of choice for infratentorial lesions. [40]

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