Thoracic outlet syndrome

Thoracic outlet syndrome (TOS) consists of a group of distinct pathologies arising as a result of compression of structures at the thoracic outlet. The structures at risk are, from anterior to posterior, the subclavian vein, subclavian artery and brachial plexus. Compression or impingement causes venous (VTOS), arterial (ATOS) or neurogenic (NTOS) TOS. NTOS is the most common presentation, caused by compression of the brachial plexus at the scalene triangle or pectoralis minor space. Other compression syndromes at the carpal and cubital tunnels should be excluded. Management is usually conservative, employing physiotherapy and postural exercises, but pain or muscle wasting may be indications for surgery. VTOS is caused by compression of the subclavian vein at the costoclavicular junction, resulting in venous thrombosis, the Paget-Schroetter syndrome, often as a result of exercise in fit young muscular people or musicians. Positional swelling of the upper limb without thrombosis is termed McCleery's syndrome. In the presence of thrombosis, clot lysis, first rib excision and venoplasty may be indicated. ATOS occurs due to compression of the subclavian artery at the scalene triangle, often in association with an anomalous bony structure, such as cervical rib, causing post-stenotic aneurysmal dilation of the artery, thrombosis and embolization. Acute upper limb ischaemia necessitates urgent cervical rib excision and arterial reconstruction.