Thoracic Outlet Syndrome

Thoracic outlet syndromes result from compression of the neurovascular structures supplying the upper extremity.

Symptoms and signs arise from intermittent or continuous pressure on elements of the brachial plexus (> 90% of cases) or the subclavian or axillary vessels (veins or arteries) by a variety of anatomic structures of the shoulder girdle region.

The neurovascular bundle can be compressed between the anterior or middle scalene muscles and a normal first thoracic rib or a cervical rib.

Most commonly, thoracic outlet syndromes are caused by scarred scalene neck muscle secondary to neck trauma or sagging of the shoulder girdle resulting from aging, obesity, or pendulous breasts.

Faulty posture, occupation, or thoracic muscle hypertrophy from physical activity (eg, weight-lifting, baseball pitching) may be other predisposing factors.

Clinical Findings

Thoracic outlet syndromes present in most patients with some combination of four symptoms involving the upper extremity: pain, numbness, weakness, and swelling.

The predominant symptoms depend on whether the compression chiefly affects neural or vascular structures.

The onset of symptoms is usually gradual but can be sudden.

Some patients spontaneously notice aggravation of symptoms with specific positioning of the arm.

Pain radiates from the point of compression to the base of the neck, the axilla, the shoulder girdle region, arm, forearm, and hand.

Paresthesias are common and distributed to the volar aspect of the fourth and fifth digits.

Sensory symptoms may be aggravated at night or by prolonged use of the extremities.

Weakness and muscle atrophy are the principal motor abnormalities.

Vascular symptoms consist of arterial ischemia characterized by pallor of the fingers on elevation of the extremity, sensitivity to cold and, rarely, gangrene of the digits or venous obstruction marked by edema, cyanosis, and engorgement.

Symptoms can be provoked within 60 seconds > 90% of the time by having a patient elevate the arms in a “stick-em-up” position (ie, abducted 90 degrees in external rotation).

Reflexes are usually not altered.

Obliteration of the radial pulse with certain maneuvers of the arm or neck, once considered a highly sensitive sign of thoracic outlet obstruction, does not occur in most cases.

Imaging and Other Studies

Chest radiography will identify patients with cervical ribs (although most patients with cervical ribs are asymptomatic).

MRI with the arms held in different positions is useful in identifying sites of impaired blood flow.

Intra-arterial or venous obstruction is confirmed by angiography.

Determination of conduction velocities of the ulnar and other peripheral nerves of the upper extremity may help localize the site of their compression.

Differential Diagnosis

Thoracic outlet syndrome must be differentiated from osteoarthritis of the cervical spine, tumors of the superior pulmonary sulcus, cervical spinal cord, or nerve roots, and periarthritis of the shoulder.

Treatment

Treatment is directed toward relief of compression of the neurovascular bundle.

Greater than 95% of patients can be treated successfully with conservative therapy consisting of physical therapy and avoiding postures or activities that compress the neurovascular bundle.

Operative treatment, required by < 5% of patients, is more likely to relieve the neurologic rather than the vascular component that causes symptoms.