Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 95. Peripheral Nerve Disorders

Topics: Introduction | Disorders of Muscle Stimulation | Disorders of the Neuromuscular Junction | Plexus Disorders | Thoracic Outlet Syndromes | Mononeuropathy | Mononeuritis Multiplex | Polyneuropathy | Hereditary Neuropathies | Spinal Muscular Atrophies

Thoracic Outlet Syndromes

Thoracic outlet syndromes are an ill-defined group of disorders that cause pain and pins-and-needles sensations (paresthesias) in the hand, shoulder, and arm.

The thoracic outlet is the passageway between the neck and the chest, through which the esophagus, major blood vessels, trachea, and many nerves pass. Because this passageway is very crowded, problems can occur when blood vessels or nerves to the arm become compressed between a rib and the overlying muscle. However, the exact cause of these disorders is often unclear. Very rarely, the cause is a clear-cut anatomic abnormality, such as an extra little rib in the neck (cervical rib) that compresses an artery or a blockage of one of the subclavian arteries. (The subclavian arteries are located under the collarbone and supply blood to the arms.)

Symptoms and Diagnosis

Pain and pins-and-needles sensations are felt usually along the inner surface of the arm and sometimes down the side. If one of the subclavian arteries is compressed, the hands, arms, and shoulders may swell or the overlying skin may look bluish because the oxygen supply is inadequate (a condition called cyanosis). Sometimes the compression is severe enough to cause Raynaud's syndrome, in which the fingers turn white when exposed to cold. In severe cases, compression may cause gangrene in the fingers.

The diagnosis is suggested by a combination of information from the history, physical examination, and several diagnostic procedures. Nerve conduction studies and electromyography (see Section 6, Chapter 77) may detect abnormalities characteristic of thoracic outlet syndrome. Through a stethoscope placed on the collar bone or near the top of the armpit, doctors may hear sounds indicating abnormal blood flow (bruits) in a compressed artery. Angiography of the arteries in the arm (brachial arteries) may be performed to detect abnormal blood flow. In this procedure, x-rays are taken after a radiopaque dye is injected into the bloodstream. However, none of these procedures can definitively confirm or rule out the diagnosis of thoracic outlet syndrome.

Treatment

For most people with symptoms of thoracic outlet syndrome, physical therapy and exercise result in improvement. Surgery may be needed if an anatomic abnormality or blockage of the subclavian artery is confirmed. However, because a definitive diagnosis is difficult to make and because symptoms often persist after surgery, most doctors try to avoid surgery.