I can only tell you that I had something similar many years ago on my brain MRI. I think it was called a "flair".

I was freaked out about it, but it was noted that it was likely due to aging, and I had a great neurologist at the time who was very well respected so I trusted him when he told me not to worry.

If you're really concerned, you can always see another neurologist for a 2nd opinion of the MRI results.