Laura -

Typically, TOS is diagnosed by ruling out other problems. People can still have TOS (as LadyLaura mentions) but not test positive on the various tests. My physiatrist believes that TOS is frequently underdiagnosed because doctors want something positive to confirm TOS. He bases his treatment on how the patient presents in the office rather than relying on a bunch of testing that may or may not show something. In my case, the testing has supported the TOS diagnosis both times around. Symptoms will vary person to person and this probably doesn't help the doctors accept it or believe it. In my own experience, my TOS symptoms are dramatically different between the two sides.

What area of the country are you in? You may want to consider consulting with another doctor that specializes in TOS. Another diagnostic test they can do is a scalene block. They inject anesthetic into the brachial plexus. If you experience temporary relief from the symptoms, this is considered positive.