The Thoracic Outlet Clinic at Baylor Medicine in Houston ... Three to four percent of cases of TOS are due to obstruction or clotting of the main vein to the arm - the subclavian vein - a condition ...

Thoracic outlet syndrome occurs when there is nerve compression ... specifically the subclavian artery and rarely the subclavian vein, which does not normally pass through the scalene hiatus.

The subclavian vein is the most anterior structure ... The neurologic symptoms suggestive of thoracic outlet syndrome that may be confused with cervical nerve root compression are pain ...