thoracic outlet syndrome


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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).

thoracic

 [thŏ-ras´ik]
pertaining to the chest (thorax); called also pectoral.
thoracic outlet syndrome compression of the brachial plexus nerve trunks and subclavian vessels, with pain in the upper limbs, paresthesia of fingers, vasomotor symptoms, and weakness and wasting of small muscles of the hand; it may be caused by drooping shoulder girdle, a cervical rib (cervical rib syndrome) or fibrous band, an abnormal first rib, continual hyperabduction of the arm (as during sleep), or compression of the edge of the scalenus anterior muscle.
thoracic surgery surgical procedures involving entrance into the chest cavity. Until techniques for endotracheal anesthesia were perfected, this type of surgery was extremely dangerous because of the possibility of lung collapse. By administering anesthesia under pressure through an endotracheal tube it is now possible to keep one or both lungs expanded, even when they are subjected to atmospheric pressure. Thoracic surgery includes procedures involving the lungs, heart, and great vessels, as well as tracheal resection, esophagogastrectomy, and repair of hiatal hernia. In order to give intelligent care to the patient before and after surgery, one must have adequate knowledge of the anatomy and physiology of the chest and thoracic cavity. It is especially important to know the difference in pressures within and outside the thoracic cavity. (See also discussion of Mechanics of Inflation and Deflation, under lung.)
Patient Care. Prior to surgery the care of the patient will depend on the specific operation to be done and the particular disorder requiring surgery. In general, the patient should be given an explanation of the operative procedure anticipated and the type of equipment that will be used in the postoperative period. The patient will be taught the proper method of coughing to remove secretions accumulated in the lungs. Although coughing may be painful in the immediate postoperative period and may require analgesic medication to relieve the discomfort, if the patient understands the need for coughing up the secretions he or she will be more cooperative. Special exercises may be given to preserve muscular action of the shoulder on the affected side and to maintain proper alignment of the upper portion of his or her body and arm. Usually the physical therapist supervises these exercises, but the nursing staff must coordinate them with other aspects of patient care.



Narcotics are rarely given before thoracic surgery because they can depress respiration. Usually the preoperative medication is atropine in combination with a barbiturate.

The development of intensive care units has sharply improved the care of the post-thoracotomy patient. The availability of monitors, ventilators, and special assist devices has increased not only the safety of the operation but also the comfort of the patient. Many patients return from the operating room with endotracheal tubes still in place, ventilated by machines, and monitored with such special equipment as Swan-Ganz catheters for observation of cardiac output, oxygenation, and level of hydration.

During the postoperative period, alteration in respiratory status is a major potential problem for patients having thoracic surgery. Impaired gas exchange can result from atelectasis, pneumothorax, mediastinal shift, bronchopulmonary fistula, pneumonia, pleural effusion, pulmonary edema, narcotics, or abdominal distention. To identify any change in respiratory status, the patient's arterial blood gases are serially monitored, breath sounds are auscultated, and the rate and character of respirations are assessed. To facilitate removal of obstructive mucus and other secretions in the air passages the patient is encouraged to deep breathe and cough every one to two hours. Chest physical therapy may be ordered to help mobilize the secretions so that they are more easily coughed up. The amount and character of sputum is noted and recorded. If necessary, nasotracheal suctioning may be done to help clear the air passages. Oxygen may be administered to prevent anoxia.

The patient is also periodically assessed for pain, abdominal distention, and alteration in cardiac function related to decreased cardiac output, arrhythmias, or cardiac tamponade. If the pericardial sac becomes filled with fluid and produces an acute cardiac tamponade, an emergency pericardiocentesis may be necessary.

Almost all patients having thoracic surgery will have chest tubes. (One exception is the patient who has had a lung removed. In this case fluid is deliberately allowed to accumulate in the pleural space to prevent mediastinal shift.) Chest tubes are attached to closed drainage systems to avoid pneumothorax and allow for drainage of the pleural space and gradual reexpansion of the lung. (See chest tube for care.)

As the operative site heals and the lung expands, the chest tubes can be safely removed. After their removal an airtight bandage is applied to the area. As a precaution against leakage of air into the chest cavity, the physician may apply petrolatum to the edges of the wound before applying the dressing.

tho·rac·ic out·let syn·drome (TOS),

collective title for a number of conditions attributed to compromise of blood vessels or nerve fibers (brachial plexus) at any point between the base of the neck and the axilla; formerly classified on the basis of presumed injurious structure or mechanism, that is, scalenus anticus syndrome, hyperabduction syndrome, costoclavicular syndrome; currently classified on the basis of the structure known or presumed to be compromised, and divided into two main groups: vascular and neurologic (simultaneous compromise of both neural and vascular structures is rare); vascular subdivisions include arterial and venous; some neurologic subdivisions remain in dispute.

tho·rac·ic out·let syn·drome (TOS),

collective title for a number of conditions attributed to compromise of blood vessels or nerve fibers (brachial plexus) at any point between the base of the neck and the axilla; formerly classified on the basis of presumed injurious structure or mechanism, that is, scalenus anticus syndrome, hyperabduction syndrome, costoclavicular syndrome; currently classified on the basis of the structure known or presumed to be compromised, and divided into two main groups: vascular and neurologic (simultaneous compromise of both neural and vascular structures is rare); vascular subdivisions include arterial and venous; some neurologic subdivisions remain in dispute.

thoracic outlet syndrome

n.
Any of several syndromes in which blood vessels or nerves are compressed, usually by an overlying muscle, as they pass from the neck region to the arm, causing pain, numbness, and weakness of the arm and hand.

thoracic outlet syndrome

an abnormal type of mononeuropathy characterized by paresthesia. It may be caused by a nerve root compression by a cervical disk.

thoracic outlet syndrome

Scalenus syndrome, thoracic outlet compression syndrome Thoracic surgery Any of the neurovascular disorders characterized by compression of the inner branches of the brachial plexus and/or subclavian artery, related among other factors, to kinking of vessels over a cervical rib, fibrous bands passing from a prominent transverse process of the 7th cervical vertebra to the 1st rib, or edge of the scalenus anterior or medius muscle(s) Clinical Pain, unilateral paresthesiae along the medial border of the arm, forearm, and little finger, ischemia, atrophy of the small hand muscles, especially of the thenar eminence, myalgia, myasthenia, with vasomotor disorders, edema and thromboses; TOS most commonly affects ♀ with osteoporosis, and may also occur in pregnancy, trauma or overstretching; compromise of this space causes the cervical rib syndrome, scalenus anticus syndrome, costoclavicular syndrome, pectoralis minor syndrome, and first rib syndrome; vascular compromise occurs in 90% of TOSs, but Sx are predominantly neurogenic

tho·rac·ic out·let syn·drome

(TOS) (thōr-as'ik owt'lĕt sin'drōm)
Collective name for several conditions attributed to compromise of blood vessels or nerve fibers (brachial plexus) at any point between the base of the neck and the axilla; classified on the basis of the structure known or presumed to be compromised, and divided into two main groups: vascular and neurologic.
Synonym(s): costoclavicular syndrome, hyperabduction syndrome, thoracic outlet compression syndrome, Wright syndrome.
References in periodicals archive ?
The "Injuries" section discusses bursitis, tendonitis, thoracic outlet syndrome and temporomandibular joint dysfunction (TJM), with each section describing the condition, its causes and prevention, and providing worthwhile links to other websites.
A conservative point of view of the thoracic outlet syndrome.
770 consecutive supraclavicular first rib resections for thoracic outlet syndrome.
The place for scalenectomy and first-rib resection in thoracic outlet syndrome.
Thoracic outlet syndrome (TOS) refers to compression of one or more of the neurovascular structures traversing the superior aperture of the chest.
Transaxillary approach for first rib resection to relieve thoracic outlet syndrome.
Their partnership at Baylor treated the largest series in the USA of lung cancer patients over 20 years (>10,000) and operated on the largest number of patients with superior sulcus carcinoma, thoracic outlet syndrome, Paget-Schroetter syndrome, and Poland's syndrome.
Video assisted sympathectomy and thoracic outlet syndrome.
Many patients with thoracic outlet syndrome develop a chronic pain syndrome (1).
The history of surgery for thoracic outlet syndrome.
Chapters on reconstructive procedures, birth palsies, and thoracic outlet syndromes have been substantially revised.

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