This is a great topic - thanks to all of you. I experienced what I considered to be "fibro fog" for many years prior to dealing with the onset of UCTD and other AI symptoms. It would generally last a day or so and then I would return to normal. It was generally manageable. In the last year or so, it seems much more chronic with certain days being worse - and then I don't feel that return to "normal" in the same way. I've never been a math or technologically oriented person - I lean towards the artistic side, and the most disturbing thing to me is loss of creative energy and thought process.
It's like I can't pull it together or maintain focus.....it all peters out before I can make something happen. And I also notice memory deficits and the inability to stay "audibly" focused. Formerly I had several creative projects going on at once outside of work, along with work, family, social life, etc. My physical fatigue has much to do with the narrowing down of all of these elements - but I've really been noticing the brain fatigue narrowing things even further and I've wondered what in the heck it means, and/or what to do about it. It's so far beyond the occasional fibro fog days, and even on "good days" I don't function nearly at the same level I did only a couple years ago. It may be the most depressing thing of all!
All of the information and comments are so helpful - I'm really grateful!
Lucy