St. Joseph Hospital of Orange
1100 West Stewart Dr, Orange, CA 92868714.633.9111
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Thoracic Outlet Syndrome

The vascular specialists at the St. Joseph Hospital Vascular Institute specialize in the diagnosis, prevention and treatment of thoracic outlet syndrome (TOS). The "thoracic outlet" is a triangular space at the base of the neck bounded by the uppermost rib and the scalene muscles. The main blood vessel (subclavian artery) that supplies blood flow to the upper extremity and large nerves (brachial plexus) that innervate the upper extremity pass through this triangular space. The main vein (subclavian vein) returning blood flow from the upper extremity passes just in front of this triangular space. Thoracic outlet symptoms can result from compression or chronic irritation of the subclavian artery or brachial plexus. Compression and chronic irritation can also lead to the acute formation of a blood clot within the subclavian vein.

Risk Factors

The most common cause of this syndrome is compression of the large nerves (brachial plexus) within the thoracic outlet. In some cases, the cause of compression is due to an anatomical abnormality such as an extra rib near the neck (a.k.a. cervical rib), extra muscle tissue or fibrous bands, or an old fracture of the clavicle, which reduces the space of the thoracic outlet. In other cases, the cause is not entirely clear and may be the result of chronic irritation due to repetitive activities that can occur with some occupations such as dental hygiene or other jobs that require the arms to be held out or overhead for long periods of time. Swimmers, other athletes and body builders have a higher risk of TOS.


Symptoms of TOS are nerve, artery or vein related and include:

  • Chronic upper extremity pain, numbness and tingling in the affected nerve distribution
  • Acute upper extremity swelling, pain and bluish discoloration due to acute blood clotting within the subclavian vein
  • Finger ulcers due to arterial embolization or aneurysmal degeneration of the subclavian artery

Other conditions can mimic the symptoms of TOS such can as a herniated disk in the neck, carpal tunnel syndrome, or even bursitis of the shoulder. Thus, this syndrome can be very difficult to diagnose, particularly when the primary problem is nerve related.

Screening and Diagnosis

A thorough patient history is paramount to diagnose TOS; however, key diagnostic clues can also be gleaned with physical examination. Plain x-rays and other types of radiological imaging (MRI, CT scan, angiogram, venogram) are often used to rule out other conditions and to evaluate for anatomical abnormalities. Special nerve tests are also used to assist in the diagnosis in most cases.


Since most cases of TOS are nerve related, treatment usually begins conservatively with modification of the work environment and physical therapy specifically designed for TOS nerve symptoms. For instance, the length of time the arms are used in outstretched or overhead positions should be reduced. Taking frequent breaks, changing positions, and stretching are also useful techniques that can be used to maintain employment. We also can help you find a work-site specialist who can evaluate your workplace to determine safe alignment, work site postures, and work-related furniture. The St. Joseph Hospital Vascular Institute has physical and occupational therapists who can teach TOS exercises that can be done at home. Good posture and overall conditioning are also key to successful conservative treatment.

If the above-mentioned conservative maneuvers are unsuccessful or when a structural abnormality such as a cervical rib is the obvious cause of symptoms, surgery can correct the problem. The procedure basically decompresses (increases the space of) the thoracic outlet by removing the first rib, scalene muscles and any other extra muscle tissue or fibrous bands that may be causing compression of the brachial plexus or subclavian artery. If the subclavian vein acutely thrombosis due to a blood clot, it is best to swiftly reopen the vein with clot-dissolving drugs. Once this is accomplished, surgical decompression of the thoracic outlet as described above is performed to decrease the chance of recurrence. Results of thoracic outlet surgery are overwhelmingly good for all three types of TOS.