Thoracic Outlet Syndrome

Thoracic outlet syndrome (TOS) is a group of disorders characterized by paresthesias, pain and weakness of the upper extremities due to compression, tension or inflammation of the neurovascular bundle as it passes through the thoracic outlet. There are 3 forms of TOS with different clinical pictures and etiologies: neurogenic TOS (NTOS) that can be divided into true or disputed forms, arterial TOS (ATOS) and venous TOS (VTOS) (see these terms).

Epidemiology

The diagnosis of TOS remains controversial so the true incidence is unknown. Neurogenic TOS is the most frequently observed form accounting for 95% of all cases with 99% of these being disputed NTOS.

Clinical description

Compression typically occurs at the interscalene triangle, the costoclavicular space between the first thoracic rib and clavicle, or the subcoracoid space beneath the pectoralis minor tendon causing pain, paresthesias and weakness in the upper extremities. Patients are unable to maintain the position of opening and closing hands while arms are in an elevated position for 3 minutes (the Roos test).

Etiology

Depending on the subtype, TOS is due to subclavian vein obstruction (in VTOS), subclavian artery compression (in ATOS) or lower trunk brachial plexus compression, scarring of scalene muscles, poor posture or a congenital anomaly (in NTOS).