I think I found the word that describes best one the main symptoms I am dealing with (other than dizziness, nausea, headaches,...): cognitive stamina.

I can solve a well defined task, sometimes better than a lot of people (I used to have high IQ) but I cannot work on a project. The latter usually involve many steps of thinking, gathering and multitasking and a lot of stamina.

For example I had to pay lawyers 10K to do some paperwork for my GC that anyone could have done on their own given the time (and I have plenty of time being off work).

At the same time, I was able to solve a 15 mins maths problem better than my smart brother. So I know that among other things it is a stamina issue.

Here is the issue: one of my neuros I am pretty sure thinks I am malingering. She asked for a neuropsych test, which I think she will use to evaluate my sick leave.

Sure the test will reflect some stamina issue, but is not equivalent to a project in complexity. Rather a series of tasks. So I might Ace the test while and confirm the suspicion of my neuro.

This is not mentioning the fact that I have major vision/convergence issues that make it impossible for me to work until my convergence is normalized...