I agree- most tests show no compression which makes diagnosis difficult. But I remember in the hospital he showed me the scan, pointed to the area and said "see it's supposed to have more space here. You dont have enough room and you're getting compression on the subclavian vein." He knew it was TOS, which made me very lucky. Dr. Dennis Bandyk, Vascular Surgeon and Professor at UCSD. He did mention later we went straight to surgery due to the DVT, but for him to see the problem was a huge relief for me.