Hi Zeara
Welcome to NeuroTalk

.
FLAIR is a MRI method which suppresses signals from fluids. The effect of this is that solid tissues are focused on. It can be used as part of diagnosis of MS.
The MS forum (
https://www.neurotalk.org/forum17/) is very active so you could ask there if any members who live with MS know more about FLAIR in this context.
Best wishes.