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.
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>.
