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What is Thoracic Outlet Syndrome (TOS)? 


Grey's Anatomy Plate
Courtesy of Wikepedia
This page explains the basics of Thoracic Outlet Syndrome, for more extensive information please visit our Research Library
Where is the Thoracic Outlet? 
The Thoracic Outlet region is located on the side of the neck towards and across the upper chest. This area is bound by the first rib, clavicle, scapula, sternum and the cervical-thoracic spine.  This region is highly complex, highly vascular and contains vital structures such as the subclavian vein, subclavian artery and the Brachial Plexus. The thoracic outlet region contains additional vital structures such as the Phrenic nerve, Long Thoracic nerve and Vertebral Artery. Additional structures are the scalene musles.  
What is Thoracic Outlet Syndrome(TOS)?  For symptoms of TOS Click here
Thoracic Outlet Syndrome is a complex condition involving compression, irritation or direct injury of major structures within the thoracic outlet such as the subclavian vein, subclavian artery and the Brachial Plexus. TOS can be very painful, debilitating and sometimes life and limb threatening. TOS can be a very difficult condition to diagnose and treat. Surgical and non surgical outcomes vary with every patient.

What causes Thoracic Outlet Syndrome?
Thoracic Outlet Syndrome can be caused be several different reasons such as but not limited to: repetitive strain, motor vehicle accidents, congenital(extra cervical ribs) or other traumatic injuries.  
There are three main types of TOS
Neurogenic TOS usually involves compression or direct injury of the Brachial Plexus. Neurogenic TOS is the most controversial of all types as symptoms are vast and often EMG studies are inconclusive. Many TOS physicians do not consider EMG studies reliable enough to make a diagnosis of Neurogenic TOS without further testing. It is common to have completely normal EMG studies with positive neurological objective and subjective findings.  Nevertheless, Neurogenic TOS can be extremely painful and debilitating. 

Venous TOS or some may call it, "effort induced" or "Paget Schroetter's Syndrome" occurs less frequently than Neurogenic TOS. Venous TOS most often involves the subclavian vein and is usually (not absolutely) caused by compression of the subclavian vein between the first rib and the clavicle. Venous TOS is usually quite dramatic in that patients tend to have obvious clinical signs and symptoms associated with compression or complete occlusion of the subclavian vein. (Deep vein thrombosis or blood clot) Venous TOS can be quite serious and can lead to life threatening complications such as a Pulmonary Embolism (blood clot in lung). Venous TOS is relatively easy to identify as vascular tests are usually able to detect a clot, narrowing within the vein or compression of the vein with arm movement. These tests can be invasive but are extremely accurate.
Arterial TOS also occurs less frequently than Neurogenic and is most often caused by an extra cervical rib compressing the subclavian artery. As with venous TOS, Arterial TOS is often easily identified with vascular diagnostic testing. Often arterial TOS presents with dramatic signs and symptoms and can be life and/or limb threatening if not resolved in a timely manner.

Note: *It is possible to have a combination of neurogenic and vascular TOS with associated signs and symptoms of both.  Some physicians believe that a combination of both always exists. In addition, some physicians believe that the main cause of pain is due to lack of blood flow to the brachial plexus which in turn causes pain related symptoms.
content reviewed by Chief Medical Editor, Dr. Carlos Selmonoksy
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