Did you ever have PEM like symptoms? I can identify with the symptoms you posted as well as the linked post. My cognition is often very poor. No short term memory. A piece of paper is my short term memory but even if I write a few things down I am still confused and often don't remember what I am writing. I can do things by reflex but having to think in real time is often an intractable problem. My brain just feels like its on fire a lot of the timeI don't get any PEM or crashes at all, or at least they arn't noticable. And my condition hardly fluctuates in any way, it just seems to be a permenant degradation with all my symptoms. I don't appear to have any major problems with my energy levels either, I just feel generally sluggish, weak and low on stamina all the time, more so as my condition deteriorates.
I definitelly think it's another disorder and not actual ME. I've sadly seen many people on here in a similar boat, testing positive for Lyme, Candida, or growth hormone deficiency for example after being previously diagnosed with ME/CFS or Fibromyalgia.
The brain issues you speak of sound like they could be related to some sort of neurotransmitter imbalance perhaps, rather than the brain degrading itself.
I have emailed and messaged patients on other forums and Facebook who have symptoms similar to mine and they have had no luck either it seems, despite more tests and investigations being done than in my case. It does seem to be something very rare I have, although probably more straightforward than anything like ME/CFS or fibro, and likely treatable in some way.
Currently I live with my mum who is also unable to work due to health problems. Both of us have just barely have enough money to pay the bills now. I was about go to university before suddenly becoming ill, and now I have no chance of getting a job or doing anything with my life now, all my prospects are gone for the time being. The fact I have this illness on top of having Asperger's syndrome makes things even more difficult, and makes some things seem impossible now.
I'm a musician and still play sometimes with bands but it's becoming hard work for me now with this condition . I need my bandmates to transport my equipment and set it up on the stage for me. And for me, it's simply a matter of showing up and getting the job done. I'm always having people at gigs congratulating me and wishing me luck on my future career, often calling me names like "Rick Wakeman", etc which depresses me so much as I feel like I have no future now and others have no idea of the pain I'm really in. Nonetheless, I'm still glad to be out doing something that gives my life some sort of meaning and purpose while I still can.
In the meantime I will continue trying anything I can and continue seeking help from others. It is not selfish at all to reach out and ask others for help, especially when you're in a constant state of suffering all the time with an illness and they can help you in some way.