Hi.....I've been a victim of autoimmune encephalitis. I didn't suffer the pain you're describing, but a young woman, Susan Cahallan, wrote a book actually titled "Brain on Fire." It's not a masterpiece, I'll warn you, however it does outline her experience with autoimmune encephalitis. It was good of her to write it.
We don't much about this condition, I believe the latest thinking is that encephalitis leads to autoimmune encephalitis and I had some strange symptoms beforehand, but I also have two different types of epilepsy and a heart condition (7 stents), plus 2 other neurological illnesses apart from ME. It gets rather difficult to sort things out.
There is also a type of documentary by the same name, but in all honesty, it's pretty bad (or at last I thought).
The usual way of testing for this is via a spinal tap that is then sent to the Mayo Clinic (they have tests they run). I had two taps a few weeks apart as I was hospitalized for ???? at the time. The test is much easier than when I had my first one some 30+ years ago. You do have to have your back facing up and then lay flat for approx. 24 hrs.(on your back) so there is no headache reaction. The mind can quickly be affected, so a psychiatrist is often used in addition to the usual MRI's, CAT scans and other tests.
I was in a coma for ?? and had a headache for about a year, but I did come out of it with everything working fairly well. Words are elusive at times, but I walk, talk, etc. Susan Cahallan was one of the early patients, very young and no one could figure out her problem.
The Mayo Panel confirmed both times that I had AE, but I've never had a recurrence. I would see your neurologist. Yours, Lenora