Roos Test / Elevated Arm Stress Test for TOS Thoracic Outlet Syndrome is defined as a neurovascular symptom complex associated with compression of the brachial bundle, which includes the brachial plexus and/or subclavian vessels. This compression may be caused by several anatomical structures in one or more of the following three compartments: the interscalene triangle, the costoclavicular space or retropectoralis minor space. The Roos Test is believed to stress all three intervals since this po