Long story due to work comp - didn't get much help from MDs as my sx kept moving around.

Had best luck w/ skilled & expert chiropractor & some advanced very good PTs.
chiro & 2 PTs dx'd TOS but no MD would commit to it.
Cervico-thoracic spine strain w/ arm pain - was what one MD wrote.
That MD didn't even do any of the basic positional tests - his adv PT guy did it tho and he agreed w/TOS.

I think I was very lucky to be able to be off work and finally stumble upon that really good chiro.
ENG/NCV neg
MRI- minor c 4/5/6 spurs all else OK
the positional blood flow tests - yes- pulse stopped when arms raised out & up
EAST test -hands turned white and lost coordination at about 30 seconds

but a small % of normals will have the blood flow stop too, so that alone is not conclusive.
But add in all the other stuff ....

Some have mild/moderate cases of TOS and unfortunately some have very severe cases of it.