Another thing I forgot to mention is that some doctors take note of and inspect is at what angle your veins drain. With TOS, it takes a higher angle for the veins to drain out. So the doctor will have you raise your arm from straight down and then gently and slowly raise your arm (while you let your arm be passive) at 45, 60 and 90 and higher, the veins drain of blood and on the back of the hand/arm veins get flattened as you raise your arm. When the veins are flat, they record that angle.

Doctors take note of at what angle the veins get flat. The worse your impingement is, the higher the angle (more vertical) when the veins lie flat. They compare the Right and Left sides.

There is a specific "normal" angle when the veins should empty. (I do not know what it is, sorry!)

I hope that helps.