Thoracic Outlet Syndrome Health Article

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.