Thoracic Outlet Syndromes
Thoracic outlet syndrome (TOS) refers to compression of one or more of the neurovascular structures traversing the superior aperture of the chest. Previously, the name was designated according to the etiologies of compression, such as scalenus anticus muscle, costoclavicular ligament, hyperabduction, cervical rib, or first rib syndromes. Peet coined the term "thoracic outlet syndrome" in 1956 to designate compression of the neurovascular bundle at the thoracic outlet.
Nerve Compression
The symptoms of nerve compression most frequently observed are pain, paresthesias (numbness and tingling) and motor weakness. Pain and paresthesias are segmental in 75% of cases, 90% involving the ulnar nerve distribution. The onset of pain is usually insidious and commonly involves the neck, shoulder, arm, and hand. The pain and paresthesias may be precipitated by strenuous physical exercise or sustained physical effort with the arm in abduction and the neck in hyperextension.
Vein Compression
The axillary subclavian vein traverses the tunnel formed by the clavicle and subclavius muscle anteriorly, the scalenus anticus muscle laterally, the first rib posterior-inferiorly, and the costoclavicular ligament medially. In most patients with thrombosis of the axillary subclavian vein (Paget-Schroetter Syndrome), the costoclavicular ligament congenitally inserts further lateral than normal. Thus, when the scalenus anticus muscle hypertrophies the vein is occluded, rather than simply compressed.
Arterial Compression
Aneurysm (with emboli) or occlusion of the artery may occur. The diagnosis is suspected by the history, physical examination, and Doppler studies and is confirmed with arteriography. Therapy for arterial compression depends on its degree of involvement. Symptoms of arterial compression include coldness, weakness, easy fatigability of the arm and hand, and pain that is usually diffuse.
Sympathetic Compression
Compression of the sympathetic nerves in the thoracic outlet may occur alone or in combination with peripheral nerve and blood vessels. The sympathetics are intimately attached to the artery as well as adjacent to the bone. It may cause atypical chest pain (pseudoangina) which simulates cardiac pain, or excessive cold, sweaty upper extremities.