Thoracic outlet syndrome: anatomy.

The thoracic outlet region contains three important structures: the brachial plexus, the subclavian artery, and the subclavian vein. As they travel from the upper mediastinum to the upper extremity, these structures run through three important spaces: the interscalene triangle, the costoclavicular space, and the subpectoral space. Compression can occur in any of these three spaces because of structural anomalies or trauma.