i am actually trying to drive this point across in another thread. VTOS and NTOS are two totally different disease processed. VTOS is by definition compression of the subclavian vein at costoclavicular space ( the space between your collar bone and your first rib ) NTOS is the compression of brachial plexus in scalene triangle (triangle consist of anterior scalene, middle scalene and first rib ) These are two separate spaces. In my experience ( close to 260 cases in the past two years). the best diagnostic test is a invasive procedure called venogram ( done by a catheter in the affected arm vein and contrast dye injected under x-ray ) this is the gold standard for VTOS dx. MRI or MRV or MRA is not the test of choice. the universal symptom of VTOS( aka effort thrombosis) is arm swelling.