Thoracic Outlet Syndromes

Thoracic Outlet Syndromes

Thoracic outlet syndromes are a group of disorders that cause pain and abnormal nerve sensations in the neck, shoulder, arm, and/or hand.

 

Description

The thoracic outlet is an area at the top of the rib cage, between the neck and the chest. Several anatomical structures pass through this area, including the esophagus, trachea, and nerves and blood vessels that lead to the arm and neck region. The area contains the first rib; collar bone (clavicle); the arteries beneath the collar bone (subclavian artery), which supply blood to the arms, a network of nerves leading to the arms (brachial plexus); and the top of the lungs.

Pain and other symptoms occur when the nerves or blood vessels in this area are compressed. The likelihood of blood vessels or nerves in the thoracic outlet being compressed increases with increased size of body tissues in this area or with decreased size of the thoracic outlet. The pain of thoracic outlet syndrome is sometimes confused with the pain of angina that indicates heart problems. The two conditions can be distinguished from each other because the pain of thoracic outlet syndrome does not appear or increase when walking, while the pain of angina does. Also, the pain of thoracic outlet syndrome usually increases if the affected arm is raised, which does not happen in cases of angina.

There are three types of thoracic outlet syndromes: (Cf. next excerpt, NINDS)

  • True neurogenic thoracic outlet syndrome is caused by a compression of the nerves in the brachial plexus. Abnormal muscle or other tissue causes the problem.
  • Arterial thoracic outlet syndrome is caused by compression of the major artery leading to the arm, usually by a rib.
  • Disputed thoracic outlet syndrome describes patients who have chronic pain in the shoulders and arms and have no other disease or syndrome, but the underlying cause cannot be accurately determined.

What is Thoracic Outlet Syndrome?

TOS is an umbrella term that encompasses three related syndromes that cause pain in the arm, shoulder, and neck: neurogenic TOS (caused by compression of the brachial plexus), vascular TOS (caused by compression of the subclavian artery or vein) and nonspecific or disputed TOS (in which the pain is from unexplained causes).  Occasionally, neurogenic TOS and vascular TOS co-exist in the same person. Most doctors agree that TOS is caused by compression of the brachial plexus or subclavian vessels as they pass through narrow passageways leading from the base of the neck to the armpit and arm, but there is considerable disagreement about its diagnosis and treatment. Making the diagnosis of TOS even more difficult is that a number of disorders feature symptoms similar to those of TOS, including rotator cuff injuries, cervical disc disorders, fibromyalgia, multiple sclerosis, complex regional pain syndrome, and tumors of the syrinx or spinal cord.  Symptoms of TOS vary depending on the type.

Neurogenic TOS has a characteristic sign, called the Gilliatt-Sumner hand, in which there is severe wasting in the fleshy base of the thumb. There may be numbness along the underside of the hand and forearm, or dull aching pain in the neck, shoulder, and armpit.

Vascular TOS features pallor, a weak or absent pulse in the affected arm, which also may be cool to the touch and appear paler than the unaffected arm. Symptoms may include numbness, tingling, aching, and heaviness.

Non-specific TOS most prominently features a dull, aching pain in the neck, shoulder, and armpit that gets worse with activity. Non-specific TOS is frequently triggered by a traumatic event such as a car accident or a work related injury.  It also occurs in athletes, including weight lifters, swimmers, tennis players, and baseball pitchers.

TOS is more common in women. The onset of symptoms usually occurs between 20 and 50 years of age. Doctors usually recommend nerve conduction studies, electromyography, or imaging studies to confirm or rule out a diagnosis of TOS.

Some of the more common provocation tests that can suggest the presence of thoracic outlet syndrome include:

  • Adson’s maneuver. For this test, you’ll be asked to turn your head toward the symptomatic shoulder while you extend your arm, neck and shoulder slightly away from your body. While you inhale, your doctor will check for a pulse on the wrist of your extended arm. If your pulse is diminished or if your symptoms are reproduced during the maneuver, your doctor considers this a positive test result, which may indicate thoracic outlet syndrome. Because false-positives often occur, your doctor may repeat the test on the unaffected side.
  • Wright test. From a sitting position and with the help of your doctor, you’ll hold your arm up and back (hyperabduction), rotating it outward, while your doctor checks your pulse to see if it’s diminished. As in the Adson’s maneuver, your doctor will want to know if your symptoms are reproduced during the test.
  • Roos stress test. From a sitting position, your doctor will ask you to hold both elbows at shoulder height while pushing your shoulders back. You will then repeatedly open and close your hands for several minutes. If your symptoms are present after the test, or if you feel heaviness and fatigue in your shoulders, this can indicate the presence of thoracic outlet syndrome.

To confirm the diagnosis of thoracic outlet syndrome, your doctor may also order one or more of the following tests:

  • X-ray. Your doctor may order an X-ray of the affected area, which may reveal an extra rib (cervical rib) and can also rule out other conditions that may be causing your symptoms.
  • Magnetic resonance imaging (MRI) scan. MRI is a painless procedure that uses a magnetic field and radio waves to create computerized images of the soft tissues of your body. These images can help your doctor determine the location and cause of compressions of the brachial plexus nerves or the subclavian artery. The scans may also reveal any congenital anomalies — such as a fibrous band connecting your spine to your rib or a cervical rib — that may be the cause of your symptoms.
  • Electromyography (EMG). This test enables your doctor to see and hear how your muscles and nerves are working. To conduct the test, a small electrode needle is inserted through your skin and into the muscles near where you’re having symptoms. The electrical activity detected by this electrode is displayed on a monitor and may be heard through a speaker.
  • Nerve conduction study. Also called nerve conduction velocity, this test measures the speed of conduction of impulses through a nerve. Doctors use the test to evaluate possible nerve damage. Small electrodes are placed on your skin over the area being tested, and a tiny electrical current is sent to the nerves in your thoracic outlet. The electrical signals produced by nerves and muscles are picked up by a computer, and the information is interpreted by a doctor trained in electrodiagnostic medicine.
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