Thoracic Outlet Syndrome (TOS)

Thoracic outlet syndrome (TOS) is a condition in which nerves and/or blood vessels in the upper chest are compressed, causing symptoms such as numbness in the fingers and discomfort in the shoulder, arm, and neck. The passageway for these nerves and blood vessels to exit the chest and supply the upper extremities is referred to as the thoracic outlet. Muscle, bone, and other tissues border the thoracic outlet. Any condition that results in enlargement or movement of these tissues of or near the thoracic outlet can cause thoracic outlet syndrome. These conditions include muscle enlargement (such as from weight lifting), injuries, an extra rib extending from the neck (cervical rib), weight gain, and rare tumors at the top of the lung. Often no specific cause is detectable.

It is felt by some scientists that the evolution of the torso of primates from a four-legged to a two-legged position may predispose humans to the development of thoracic outlet syndrome. The resulting vertical posture produced flattening of the chest cage and a shift of the shoulder joint backward, both of which narrowed the thoracic outlet.



Neurogenic thoracic outlet syndrome can also develop in people who experience trauma to the neck or chest from any accident. Sometimes, people with this condition are born with a misshapen first rib or a cervical rib, which is an extra rib located above the others. This can cause compression on the nerves in the area. The resulting scar tissue may cause pain, numbness, tingling, headaches, or weakness in the arm and hand.


Venous thoracic outlet syndrome is caused by the compression of a subclavian vein, which carries blood from the upper extremities including the shoulders, arms, and hands to the heart. This compression can lead to blood clots, which can travel to the heart and lungs and be life-threatening. People with this condition are frequently born with a narrowing of the space where the subclavian vein extends from the shoulder to the heart. Overuse of the arm and shoulder, such as during sports or work, causes the veins in the thoracic outlet to become compressed, which can lead to blood clots.


This type of thoracic outlet syndrome is caused by a blood clot in a subclavian artery, which carries blood from the heart to the arm. It occurs in people born with a cervical rib or an unusually shaped first rib, which can compress the subclavian artery. The repeated compression can lead to a permanent narrowing in the artery, causing clots to form and travel down the arm toward the hand.


The symptoms that you experience as a result of thoracic outlet syndrome will depend on whether the nerves or the blood vessels are affected.

Compressed nerves can cause:

  • Pain in parts of the neck, shoulder, arm, or hand
  • Numbness in the forearm and fingers
  • Weakness of the hand

Compressed blood vessels can cause:

  • Swelling of the arm
  • Redness of the arm
  • Hands or arms that feel cold to the touch
  • Hands or arms that become easily fatigued

You may also find it difficult to lift objects above your head. You might also have a limited range of motion in your shoulders and arms.


Thoracic outlet syndrome usually occurs when the thoracic outlet becomes narrowed and compresses the nerves and blood vessels. The cause of this compression isn’t always known. However, it may develop as a result of the following conditions:

An Extra Rib

Some people are born with an extra rib above their first rib. This reduces the size of their thoracic outlet and compresses nerves and blood vessels.

Poor Posture & Obesity

People who don’t stand up straight or who have excess abdominal fat may have increased pressure on their joints. This can cause a narrowing of the thoracic outlet.


Car accidents and other traumatic injuries can compress the thoracic outlet as well as the vessels and nerves in this area.

Overuse of the Shoulders & Arms

Repetitive activities, such as working at a computer or lifting heavy objects above the head, can cause damage to the tissues in the thoracic outlet. Over time, the size of the thoracic outlet may shrink, placing pressure on the vessels and nerves.


Making a proper diagnosis is the most important step in TOS. Doctors who treat this condition include vascular surgeons, chest (thoracic) surgeons, and vascular medicine physicians. To diagnose your condition, your doctor will perform a complete physical exam and will review the results of previous diagnostic tests. In some cases, a thorough evaluation by a skilled neurologist may be recommended to rule out cervical spine disease or other neurological conditions that may be mimicking or causing your symptoms.

Additional tests performed to diagnose thoracic outlet syndrome include:

  • Nerve conduction studies (to evaluate the function of the motor and sensory nerves)
  • Vascular studies (of the arteries or veins)
  • Chest X-ray to rule out cervical rib abnormalities
  • Cervical spine X-rays to rule out a cervical rib (extra rib) or cervical (neck) spine abnormalities
  • Computed tomography (CT) scan and magnetic resonance imaging (MRI) of the chest
  • CT scan or MRI of the spine to rule out cervical spine impingement (pressure), which can mimic neurogenic thoracic outlet syndrome
  • Magnetic resonance imaging with angiography (MRA) to view blood vessels
  • Arteriogram/venogram (X-ray that uses dye to look at blood flow)
  • Blood tests

Treatment & Prevention

Physical therapy: You’ll do exercises to stretch and strengthen muscles in your neck and shoulders and improve your posture. This may be all you need to get relief.

Medication: The doctor may recommend that you use a muscle relaxant or that you take ibuprofen or naproxen to ease pain and swelling. You may hear your doctor call these NSAIDs or non-steroidal anti-inflammatory drugs.

Botox shots: A shot into the muscle at the base of your neck can relax the area and help ease the pain. This can work for up to 3 months and be repeated if you need it. Surgery is sometimes an option, but it doesn’t work nearly as well for this type of TOS.

Venous and Arterial: First you’ll be treated for any possible blood clots. Then you’ll most likely need a type of surgery called thoracic outlet decompression. Your surgeon will open up the space for the nerves and blood vessels to pass through. They may remove extra bone or other tissue, and cut or remove muscles that are causing the compression. They’ll also fix or bypass damaged blood vessels.

  • If other treatments don’t fix your symptoms, you may need long-term pain management. You may need medication.
  • Your doctor also may recommend a few things you can do to feel better
  • Get to a healthy weight.
  • Avoid things that aggravate the condition, like carrying a heavy bag on your shoulder.
  • Take breaks often at work to move and stretch.
  • Try a massage or a heating pad on your muscles.
  • Do relaxation exercises, like visualization, autogenic relaxation (repeating a word that gives you peace), or progressive muscle relaxation (clinching then releasing different muscles).

Risk Factors

Risk factors include occupations that involve heavy usage of the upper extremities against resistance, including jack-hammer operators and dental hygienists, weight lifting, pregnancy, and obesity. Any condition that causes encroachment of the space for the brachial plexus at the thoracic outlet can lead to thoracic outlet syndrome, including poor posture.

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Frequently Asked Questions

1. Is thoracic outlet syndrome serious?

Although many cases of thoracic outlet syndrome (TOS) cannot be prevented, the condition is treatable. TOS may lead to greater discomfort and impaired function if left untreated. Certain types of the condition might result in life-threatening blood clots.

2. What happens if thoracic outlet syndrome is not treated?

The thoracic gorge syndrome can cause pain in the neck and shoulders, numbness and tingling in the fingers, and a weak grip. If left untreated, TOS can lead to increased pain and decreased function. Certain forms of the disease can cause serious blood clots.

3. What is the most common type of TOS?

The most prevalent form of TOS is neurogenic TOS, which affects mostly middle-aged women (95 percent of persons with TOS have this version of the condition). Recent studies have shown that, in general, TOS is more common in women than in men, particularly among those with poor muscle development, poor posture, or both.

4. How painful is thoracic outlet syndrome?

Thoracic outlet syndrome can cause several or all of the following symptoms, Pain felt in the hand, arm, shoulder, and/or neck, which can range from dull to sharp. Weakened hand & arm that tire easily. Numbness & tingling in the shoulder, arm, & hand.