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Thoracic Outlet Syndrome

Thoracic outlet syndrome

Definition

Thoracic outlet syndrome refers to a condition that results in compression of neurovascular anatomical structures at the superior aperture of the chest (thorax).

Description

Thoracic outlet syndrome (TOS) refers to compression of nerves and blood vessels in the upper portion of the thorax. Neurologic symptoms occur in 95% of affected persons. The cause and treatment of TOS is controversial. In 95% of cases the brachial plexus is involved. The lower two nerves (C8 and T1) are most commonly affected in 90% of persons, following the ulnar nerve distribution. Blood vessels can also be affected. The subclavian vein is involved in 40% of cases and the subclavian artery in 1% of cases. The second most common nerve root involvement occurs in brachial plexus nerves C5, C6, and C7, and symptoms, if these nerves are affected, can be referred to upper back, upper chest, ear, neck, and outer arm that follows a radial nerve distribution.

Demographics

Reports concerning demographic information are controversial and range from three per 1,000 to 80 per 1,000 people. Overall the disorder is three times more common in women than men, with the exception of nervous system involvement which is more common in males. Some reports indicate that TOS is nine times more common in females than males. In the United States the incidence of vascular or neurogenic TOS is considered rare with only one new case per million population for the neurogenic TOS. The usual age of onset is from the second to eighth decade, with a peak age of onset in the fourth decade. Arterial involvement (arterial thoracic outlet syndrome) has no specific gender predilection.

Causes and symptoms

There are three major causes of TOS which include anatomic causes, trauma/repetitive activities, and neurovascular (nerve and blood vessels) entrapment in the chest. Certain anatomic abnormalities of the muscles in the neck and first rib (and a vertebral disk, C7) can cause compression of nerves and arteries. Anatomic abnormalities account for the majority of cases of neurologic and arterial thoracic outlet syndrome. Trauma such as hyperextension injury from motor vehicle accident or effort vein thrombosis (spontaneous thrombosis of the axillary veins following vigorous arm extension) may cause thoracic outlet syndrome. Repetitive activities similar to those of musicians are especially susceptible if they maintain the shoulder in abduction or extension positions for long periods. Nerves and blood vessels can be compressed anatomically in the costoclavicular space between the first rib and the head of the clavicle.

Neurologic pain can occur on either sides of the forearm, upper back and upper chest, neck and ear. Pain is especially evident on the ring and small finger. Patients often experience nocturnal paresthesias, awakening with numbness or pain (dysesthesia). There is often a loss of dexterity, cold intolerance and headache . Venous involvement causes pain, edema (swelling), cyanosis (bluish discoloration of the skin due to lack of oxygen), and distended superficial veins of the shoulder and chest. Arterial involvement causes pain and claudication, pallor, pulselessness, lower blood pressure in affected arm, and embolization (infarcts) of hand and finger. Patients usually have a subtle weakness of affected limb.

Diagnosis

Chest x ray may reveal an anatomic abnormality. Color flow duplex scanning (ultrasound analysis) is indicated for suspected case of vascular thoracic outlet syndrome. If symptoms suggest arterial involvement an arteriogram may be indicated as well as venography (in suspected cases of venous involvement). Nerve conduction evaluation by nerve root stimulation is the best approach to diagnose neurologic thoracic outlet syndrome.

Treatment team

The treatment team usually consists of appropriate specialists which depend on the presentation. Specialists that can be consulted include a neurologist , vascular surgeon or orthopedic surgeon. Physical medicine physicians are required for outpatient workup and evaluation.

Treatment

Neurologic TOS requires outpatient referral and conservative outpatient physiotherapy. Vascular thoracic outlet syndrome requires more urgent care that typically includes immediate heparinization, vascular surgery consultation, color flow (ultrasound), duplex scanning and angiography or venography. Neurologic thoracic outlet syndrome patients may also require surgery if conservative medical therapy fails for more than four months. However, surgical results are not encouraging since a study demonstrated that 60% of postsurgical patients were still work disabled one year after surgery. Outpatient medications can include Coumadin (a blood thinner or anticoagulant), analgesics or short-term antidepressants if there is protracted pain.

Recovery and rehabilitation

Recovery includes stress avoidance and work simplification and modifications on the job site. Recommendations include avoidance of sustained muscular contraction and repetitive or overhead work. Exercise programs may help with chronic pain. Exercises are recommended to maximize the potential outlet space through special stretching and strengthening maneuvers of the shoulder. These exercise can include maneuvers such as bilateral (both sides) shoulder retraction while standing or lying prone, standing corner pushups, hand circles and cervical and lumbar spine extension. Outpatient management typically includes occupational/physical therapy, and manipluation. Inpatient treatment is not indicated unless the patient is a surgical candidate.

Clinical trials

There are projects funded by the National Institute of Neurological Diseases and Stroke <http://www.ninds. nih.gov> concerning pain and pain management. The projects forcus on seeking new treatments for nerve damage and pain.

Prognosis

Neurologic TOS is not progressive and but requires treatment. Arterial or venous thoracic outlet syndrome respond well to adequate treatment and the results are generally good. Some patients can develop chronic pain (neurologic type) or thrombosis (venous and arterial thoracic outlet syndrome). Other complications that can develop include loss of functional ability of arms, neurologic deficit, depression , and ischemia.

Special concerns

Pregnancy can cause an increase in TOS symptoms, because of increased body size and displacement of the abdomen. Increased breast size common during and after pregnancy can displace the shoulder girdle and cause postural changes that can precipitate symptoms. Patients should be educated concerning precipitating factors of TOS, which can decrease the likihood of recurrence.

Resources

BOOKS

Goetz, Christopher G., et al., eds. Textbook of Clinical Neurology, 1st ed. Philadelphia: W. B. Saunders Company, 1999.

Marx, John A., et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice, 5th ed. St. Louis: Mosby, Inc., 2002.

Townsend, Courtney M. Sabiston Textbook of Surgery, 16th ed. W. B. Saunders Company, 2001.

WEBSITES

National Rehabilitation Information Center. <http://www.naric.com>.

ORGANIZATIONS

American Chronic Pain Association. P.O. Box 850, Rocklin, CA 95677-0850. (916) 632-0922 or (800) 533-3231; Fax: (916) 632-3208. ACPA@pacbell.net. <http://www.theacpa.org>.

Laith Farid Gulli, MD

Nicole Mallory, MS, PA-C

Alfredo Mori, MBBS

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"Thoracic Outlet Syndrome." Gale Encyclopedia of Neurological Disorders. . Encyclopedia.com. 30 Apr. 2017 <http://www.encyclopedia.com>.

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"Thoracic Outlet Syndrome." Gale Encyclopedia of Neurological Disorders. . Retrieved April 30, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/thoracic-outlet-syndrome

Thoracic Outlet Syndrome

Thoracic Outlet Syndrome

Definition

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:

  • 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.

Thoracic outlet syndrome is most common in women who are 35 to 55 years of age.

Causes and symptoms

Compression of blood vessels or nerves in the thoracic outlet causes pain and/or abnormal nerve sensations. Compression usually occurs at the location where the blood vessels and nerves pass out of the thoracic outlet into the arm.

There are several factors that contribute to a person developing thoracic outlet syndrome. Poor posture is a major cause and is easy to treat. A person's physical makeup also can cause thoracic outlet syndrome. For example, abnormalities of certain anatomical structures can put pressure on blood vessels or nerves. Typical abnormalities that can cause problems are malformed ribs and too narrow an opening between the collar bone and the first rib.

The main symptom is pain in the affected area. The patient can also develop weakness in the arm and hands, tingling nerve sensations, and a condition called Raynaud's syndrome. In Raynaud's syndrome, exposure to cold causes small arteries in the fingers to contract, cutting off blood flow. This causes the fingers to turn pale. In very severe cases of blood vessel compression, gangrene can result. Gangrene is the death of tissue caused by the blood supply being completely cut off.

In the case of arterial thoracic outlet syndrome, the artery beneath the collar bone leading to the arm is compressed, causing the artery to increase in size. Blood clots (thrombi) may form in the blood vessel. When blood vessels are compressed, the hands, arms, and shoulders do not receive proper blood supply. They can swell and turn blue from a lack of blood.

In the case of true neurogenic thoracic outlet syndrome, the nerves most affected are those of the network of nerves supplying the chest, shoulder, arm, forearm, and hand (brachial plexus). When a nerve is affected in thoracic outlet syndrome it produces a tingling sensation (paresthesia). It can also cause weakness in the hand and reduced sensation in the palm and fingers.

Diagnosis

There are no specific diagnostic tests for thoracic outlet syndromes. The diagnosis is made by ruling out other diseases and by observing the patient. Two nonspecific tests that can suggest the presence of thoracic outlet syndrome are the Adson test and the Allen test. In the Adson test, the patient takes a deep breath and tilts his or her head back and turns it to one side. The physician tests to see if the strength of the patient's pulse is reduced in the wrist on the arm on the opposite side of the head turn. In the Allen test, the arm in which the patient is experiencing symptoms is raised and rotated while the head is turned to the opposite side. The physician tests to see if the pulse strength at the wrist is reduced. If the strength of the pulse is reduced in either of these two tests it indicates compression of the subclavian artery.

Occasionally, examination with a stethoscope may reveal abnormal sounds in affected blood vessels. X rays can reveal constrictions in blood vessels if a special dye is injected into the blood stream to make the blood vessels visible (angiography ).

Certain tests are available to help with the diagnosis of nerve compression. These include the nerve conduction velocity test and somatosensory evoked potential test. In the nerve conduction velocity test, electrodes are placed at various locations on the skin along a nerve that is being tested. A mild electrical impulse is delivered through an electrode at one end of the nerve and the electrical activity is recorded by the other electrodes. The time it takes for the electrical impulse to travel down the nerve from the stimulating electrodes to the recording electrodes is used to calculate the nerve conduction velocity. This can be used to determine if any nerve damage exists.

In a somatosensory evoked potential test, electrodes are placed on the skin at the scalp, neck, shoulder, and wrist. A mild electrical impulse is delivered at the wrist, and a recording is made of the response by the brain and spinal cord. This test also can determine the presence of nerve damage.

Treatment

The main treatment for thoracic outlet syndrome is physical therapy. Exercises aimed at improving the posture of the affected person are also useful. In some cases, surgery can be performed to remove the cervical rib if this is causing the problem and physical therapy has failed to work. However, surgery is generally not used to treat thoracic outlet syndrome.

Prognosis

Treatment of true neurogenic and arterial thoracic outlet syndromes is usually successful. Treatment of disputed thoracic outlet syndrome is often unsuccessful. This may relate to the uncertainty of the underlying cause of the pain.

Resources

BOOKS

Berkow, Robert, editor. Merck Manual of Medical Information. Whitehouse Station, NJ: Merck Research Laboratories, 1997.

KEY TERMS

Angina A severe constricting pain in the chest, usually caused by a lack of oxygen to the heart.

Neurogenic Caused by nerves; originating in the nerves.

Subclavian Located beneath the collarbone (clavicle).

Cite this article
Pick a style below, and copy the text for your bibliography.

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"Thoracic Outlet Syndrome." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. 30 Apr. 2017 <http://www.encyclopedia.com>.

"Thoracic Outlet Syndrome." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. (April 30, 2017). http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/thoracic-outlet-syndrome

"Thoracic Outlet Syndrome." Gale Encyclopedia of Medicine, 3rd ed.. . Retrieved April 30, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/thoracic-outlet-syndrome