PTSD symptoms
There are a lot of good resources including books that describe PTSD and its symptoms. I recommend the book The body keeps the Score. He describe many of the symptoms I experience much better than I ever could. However, the effects are so devastating, that they do require repeated and multiple explanations for people who have not experienced it to at least get some understanding of it.
Cognitive decline
This is probably the most annoying symptom - you can not act if you can not think.
Permanent decline
My cognitive decline after the injury was very drastic. I was able to act in autopilot mode, but when I needed to think, to plan, or to learn something new then I would hit brick wall. Event at the best estimates I felt that I am functioning at 5% of previous capacity while many areas become impossible at all. Yet, from outside, it might not seemed so bad as I still could do trivial things on autopilot and memories from past were still accessible.
In time it got a bit better, but my productivity even at best times is below 10% what it used to be. The main problem is that even average complexity problems were too complex for me now.
When stressed
When stressed my head can completely shutdown. Even if it does not shut down it becomes very hard to function. It is very easy to manipulate me as I become very suggestive.
English language deterioration
One of the interesting and noticeable impacts is how significantly my knowledge of English language drops if I am stressed. That was especially difficult when I needed to read legal documents related to my injury. Few complex sentences and I am no longer able to understand anything even if the rest of the document is in relatively simple English.
In some cases it helps if I ask for someone to read what I wrote. Well actually since the injury I have to do it with almost all text I write, including this site. So, after updating few pages I asked one support worker to read it. He told that he was able to understand my story, but asked maybe one of the parts he just read was written long time ago. That was actually the newest part and I thought I wrote it well. I was feeling only moderately stressed compared to my usual (which is highly stressed compared to normal) and I took long time to write and checked few times before asking to read. I asked why he thought so. He pointed to many errors, and there were many.
However, I have to write. Just need to keep asking to read it. I think if you look at my productivity it would be negative as I need more resources to help me, than I actually produce something useful. However, this is sad reality.