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Thoracic Outlet Syndrome

NORD is very grateful to Richard J Sanders, MD, Clinical Professor of Surgery, University of Colorado Medical School and Rose Medical Center, for the preparation of this report.

Synonyms of Thoracic Outlet Syndrome

  • TOS

Disorder Subdivisions

  • arterial thoracic outlet syndrome
  • neurogenic thoracic outlet syndrome
  • nonspecific thoracic outlet syndrome
  • Paget-Schroetter syndrome
  • pectoralis minor syndrome
  • vascular thoracic outlet syndrome
  • venous thoracic outlet syndrome

General Discussion

Thoracic outlet syndrome (TOS) is a condition presenting with arm complaints of pain, numbness, tingling and weakness. The cause is pressure in the neck against the nerves and blood vessels that go to the arm.

There are three types of TOS depending on which structure is being compressed:
1. Neurogenic TOS-nerve compression comprises 95% of all TOS patients

2. Venous TOS-compression of the main vein comprises 4% of all TOS patients

3. Arterial TOS-compression of the main artery comprises less than 1% of all TOS patients

4. Vascular TOS is a term sometimes used but there is no such entity as vascular TOS. The term refers to TOS due either to compression of an artery or vein (arterial or venous TOS). The appropriate terms, arterial or venous, should be employed and the term vascular discarded.

The three types of TOS are very different from each other. Each will be described separately.


Neurogenic TOS presents with pain, weakness, numbness and tingling in the hand and arm. Additionally, neck pain and headache in the back of the head are common.

Venous TOS, also known as Paget-Schroetter disease, presents with arm swelling, blue or dark discoloration, and a feeling of fullness or aching in the arm.

Arterial TOS presents with coldness, numbness, tingling, pain, and white discoloration in the fingers or whole hand. Cramping of the forearm and hand with activity (claudication) is common. Pain usually involves the hand and arm, but not the neck or shoulder.


Neurogenic TOS is most often caused by neck trauma, whiplash injuries or repetitive stress injury at work being the most common events that bring on symptoms. The injury results in over-stretching neck muscles which heal by forming scar tissue in the muscle. This in turn puts pressure against the nerves to the arm which causes the symptoms.

Venous TOS is often caused by strenuous use of the arm which irritates the main vein to the arm (subclavian vein) lying behind the collar bone (the clavicle). Pressure against the vein is due to variations in normal anatomy. Most people have adequate room for the main vein to travel from the arm to reach the heart. However, some people are born with a very narrow space through which the vein travels. These people are the ones who can develop obstruction and clots in the vein from excessive arm and shoulder activity.

Arterial TOS is caused by clot formation in the artery to the arm (subclavian artery) in the area just behind the collar bone. Even when a clot forms, most people do not develop symptoms until the clot breaks into small pieces which flow down the arm to block arterial circulation at the elbow or hand. The clot formation is due to changes in the artery as a result of a congenital extra rib, called a cervical rib or abnormal first rib.

Affected Populations


Related Disorders

Pectoralis minor syndrome (PMS) is a condition causing pain, numbness and tingling in the hand and arm. It often coexists with thoracic outlet syndrome (TOS) but can also occur alone.

The symptoms are similar to those of TOS: Pain, weakness, numbness and tingling in the hand and arm. But in PMS there also is pain or tenderness in the chest wall below the collar bone and often in the arm pit as well. Like TOS, there may be pain above the shoulder blade in back as well as in the neck. While theoretically this can involve the nerves, vein, and artery to the arm, just like TOS, it rarely involves the vein and artery. It primarily puts pressure on the nerves.

The cause is tightness in the pectoralis minor muscle (lying just below the collar bone) which is located just under the major pec muscle in the front of the chest, under the breast. The condition is often brought about by trauma to the neck or excessive stretching of the shoulder. It is important to note that the symptoms not only are similar to TOS but that the two condtions often exist together.

The distinguishing feature of PMS is there is tenderness over the chest Wall just below the collar bone as well as tenderness in the arm pit. The best test for PMS is a pectoralis minor muscle block. Physical therapy is the initial treatment. Cutting the pectoralis minor tendon at its insertion on the bone below the collar bone (the coracoid process) is the surgical treatment.

Standard Therapies

Neurogenic TOS is diagnosed by using Aprovocative maneuvers to elicit (or provoke) symptoms. These maneuvers put the neck and arms in certain positions which put stress on the nerves to the arm to bring on the symptoms of pain, numbness and tingling in the hand, arm, and neck. Some of these maneuvers have been shown to be unreliable because positive responses are found in many healthy individuals. These include the Adson test, Roos Test, and Wright Test. Other provocative maneuvers which provide greater reliability and seldom are positive in healthy people include rotating the neck or tilt the head to one side which causes symptoms to appear on the opposite side. Another provocative maneuver is extending one arm to the side, bending the wrist upward, and tilting the head to the opposite side (called the upper limb tension test). When all of these maneuvers elicit the same symptoms a diagnosis of neurogenic TOS is highly likely.

Few tests are helpful in making the diagnosis of neurogenic TOS. The most helpful test is a scalene muscle block. This is performed by injecting a small amount of local anesthetic directly into the scalene muscles of the neck. A positive response is improvement of symptoms at rest as well as with the provocative maneuvers which occurs within one or two minutes of the injection.

Nerve tests such as EMG and NCV tests are usually normal. The one exception is that people who have an extra rib (cervical rib) plus arm weakness and atrophy of hand muscles usually have abnormal nerve tests indicating ulnar nerve abnormalities. However, recent introduction of a new nerve test, the MAC test (abreviation for medial antebrachial cutaneous nerve) has proven to be very useful, particularly in people who have symptoms in just one arm. In these people, the good arm serves as a baseline from which to compare the symptomatic arm.

X-rays are usually normal but are worth obtaining as they may demonstrate an extra rib in the neck (cervical rib). While less than 5% of people with neurogenic TOS have an extra rib, when present it is helpful in confirming a diagnosis. Newer diagnostic tests which have yet to prove themselves include MRI of the brachial plexus and injection of dye around the brachial plexus (neurography). The problem with the latter tests is that many healthy individuals demonstrate abnormalities with these examinations.

Arteriography is helpful in the diagnoses of arterial TOS but should not be used to diagnose neurogenic TOS. The reason is that healthy individuals can reveal narrowing in the artery when the arm is elevated. This makes demonstrating narrowing of an artery to the arm in patients with nerve symptoms of no value in the diagnosis of a nerve problem.

Recognition of arterial and venous TOS is usually not too difficult as there are objective tests available to confirm the diagnosis and there are very few other conditions that resemble them. However, neurogenic TOS, by far the most common type of TOS, is more difficult to diagnose because other neurogenic conditions mimic it. An understanding of the anatomy of nerves to the arm is helpful. A nerve is like a telephone wire running from a telephone pole down the street into your house. Damage to the wire anywhere along its course will produce the same result namely cutting off the phone you pick up. Nerves to your hand begin in the neck and run to the fingers like a single wire. Pressure against the nerve anywhere along its course will produce the same symptoms in the hand, namely numbness, tingling, pain, and weakness. The pressure points where this is likely to occur are at the wrist causing carpal tunnel syndrome, in the forearm producing pronator or radial tunnel syndrome, at the elbow against the ulnar nerve causing cuboid tunnel syndrome, below the collar bone under the pectoralis minor muscle eliciting pectoralis minor syndrome, at the side of the neck causing thoracic outlet syndrome, or in the cervical spine produced by cervical disc disease or cervical arthritis. Therefore pressure at any of these points elicits symptoms similar to neurogenic TOS and each of these conditions must be looked for on physical examination and tested for by diagnostic nerve studies. To make diagnosis even more confusing, these other conditions can exist along with neurogenic TOS as associated conditions (called double crush syndrome) or they may be the primary diagnosis instead of neurogenic TOS.

Venous TOS is fairly easily recognized by swelling of the entire arm and hand. Superficial veins that lie just under the skin are more prominent in the involved arm, shoulder, and over the chest wall of the involved side. The arm may or may not be dark in color.

The only tests that help diagnose venous obstruction are Doppler or duplex examinations and venography (injecting dye in to the vein of the arm).

Arterial TOS is recognized by a hand that is colder and paler than the opposite normal hand of that person. The pulse at the wrist is usually diminished or absent.

Tests helpful in the diagnosis of arterial TOS are non-invasive pulse-volume recordings (non-invasive vascular lab studies) and arteriography (injecting dye into the artery).

There are essentially two ways to treat TOS, non-surgical, which is called conservative, or surgical. Neurogenic TOS is always initially treated with physical therapy. Many patients improve with this treatment and nothing further is needed.

Neurogenic TOS can be treated surgically if conservative therapy fails and a patient is still having significant symptoms. Surgery involves removing pressure from the nerves to the arm by either removing the scalene muscles in the neck, removing the first rib which requires detaching the scalene muscles, or doing both scalene muscle and first rib removal. The choice of operations depends on the experience of the surgeon as each of these operations has about the same success rate.

Venous TOS is initially treated with thrombolytic drugs and anticoagulants (blood thinning drugs). Once the initial blood clot has been dissolved, surgery may be required to treat the underlying condition that caused the clot to prevent it from recurring.

Venous TOS is surgically treated by first rib resection including removing the bands and ligaments that surround the subclavian vein. In patients where the vein is totally occluded a bypass graft is sometimes performed to restore venous circulation from the arm.

Arterial TOS has no non-surgical treatment. Physical therapy does not help.

Surgery for arterial TOS includes two steps: First removing the extra rib or the abnormal rib; then the damaged artery is excised and circulation restored with an arterial replacement graft.

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:

Thoracic Outlet Syndrome Resources



Arthur LG, Teich S, Hogan M, Caniano DA, Smead W. Pediatric thoracic outlet syndrome: a disorder with serious vascular complications. J Pediatr Surg. 2008;43:1089-1094.

Sanders RJ. Neurogenic thoracic outlet syndrome and pectoralis minor syndrome: a common sequela of whiplash injuries. Journal of Nurse Practioners. 2008; 4: 586-594.

Sadat U, Weerakkody R, Varty K. Thoracic outlet syndrome: an overview. Br J Hosp Med (Lond). 2008;69:260-263.

Sanders RJ, Hammond SL, Rao NM. Diagnosis of thoracic outlet syndrome. J Vasc Surg.

National Institute of Neurological Disorders and Stroke. Thoracic Outlet Syndrome. Last Updated December 28, 2011. Accessed March 2, 2012.

Mayo Clinic for Medical Education and Research. Thoracic Outlet Syndrome. Updated August 2, 2011. Accessed March 2, 2012.

Sanders Richard J. Thoracic outlet syndrome. Last Updated September 2008. Accessed March 2, 2012.

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Report last updated: 2012/03/19 00:00:00 GMT+0

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