I know MS is another for demylenating autoimmune disease, but that's my diagnoses. Regardless, I have drug sensitivity so I do Copaxone (a synthetic myelin) with vegan keto diet. Keto takes a lot of research, and make sure you have the right of nutrients, RDI of vitamins and minerals, plus extra hydration for potassium etc (must avoid keto acidosis). I drink biosteel....
But think, nuts seeds coconut, Mct, pea protein, vitamins, tahini, olive oil, spices, veg powders and juices, berries etc. Anyways saw instant affect for my brain fog.

I don't do much activity, so I don't need that many calories, just follow the macros and rdi,

If you just want to eat healthy, do a Mediterranean diet and cut out anything that makes your symptoms worse (it's easier to do). Then add mct and a hood multivitamin with methylated bs....

That's what I found works for the "untreatable " symptoms, making it more bearable. I also take other supplements to help because healthy people can make all sorts of compounds, but aged or unwell people have recently been shown to benefit from certain supplements.... again this is new research, ask your doctor before starting any regime.
If Doing diet, gains keep gaining after the one and two and three year mark, even when triggers (ieweather etc) and symptoms are conistent . I found the most relief for the terrible brain fog using diet, and it may not be worth it to you for drastic dietary changes if the symptoms are different. Always have medical supervision. I have nutrition background and never thought I would do keto, because I don't eat cheese or meat or eggs, and because It is challenging and potentially dangerous. It's the only food my body will handle - I react to animal products and sugars now. I did the low fodmap thing at the beginning... that's a good starting point.
Good luck, healing thoughts to alll