I can't use my arms and hands at chest level or above, or they become dead and numb. If I'm flared up they become dead in any position. I also can't use my arms away from my body, unless they are supported. Even then, I have to keep them lowish, or they get puffy and numb.

As far as how I got it, it was an RSI, but that RSI came 10 years after an MVA whiplash injury to my neck that I had long recovered from, but I supposed might have contributed to my developing TOS. I didn't have arm and hand symptoms until 10 years after the MVA, during a time when I was working 60-70 hours a week with a terrible set up, and I had steadily worsening neck pain, and then suddenly all the vascular and nerve symptoms came on all at once, and have never gone away.