eMedicine Specialties > Emergency Medicine > Cardiovascular

Thoracic Outlet Syndrome

Author: Andrew K Chang, MD, Assistant Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
Coauthor(s): J Stephen Bohan, MD, FACP, FACEP, Director, Observation Medicine, Department of Emergency Medicine, Clinical Director, Harvard Medical School, Brigham and Women's Hospital
Contributor Information and Disclosures

Updated: Feb 4, 2008

Introduction

Background

Thoracic outlet syndrome (TOS) is a broad term that refers to compression of the neurovascular structures in the area just above the first rib and behind the clavicle. It represents a constellation of symptoms. The cause, diagnosis, and treatment are controversial. The brachial plexus (95%), subclavian vein (4%), and subclavian artery (1%) are affected. Most presentations to the emergency department (ED) are nonemergent and require only symptomatic treatment and referral.

Pathophysiology

The brachial plexus trunks and subclavian vessels are subject to compression or irritation as they course through 3 narrow passageways from the base of the neck toward the axilla and the proximal arm. The most important of these passageways is the interscalene triangle, which is also the most proximal. This triangle is bordered by the anterior scalene muscle anteriorly, the middle scalene muscle posteriorly, and the medial surface of the first rib inferiorly. This area may be small at rest and may become even smaller with certain provocative maneuvers. Anomalous structures, such as fibrous bands, cervical ribs, and anomalous muscles, may constrict this triangle further. Repetitive trauma to the plexus elements, particularly the lower trunk and C8-T1 spinal nerves, is thought to play an important role in the pathogenesis of TOS.

The second passageway is the costoclavicular triangle, which is bordered anteriorly by the middle third of the clavicle, posteromedially by the first rib, and posterolaterally by the upper border of the scapula.

The last passageway is the subcoracoid space beneath the coracoid process just deep to the pectoralis minor tendon.

Frequency

United States

Because no objective confirmatory test is available for TOS, there is much disagreement with regards to its true incidence, with reported figures ranging from 3-80 cases per 1000 people.

Sex

The sex ratio varies depending on the type of TOS (eg, neurologic, venous, arterial). Overall, the entity is approximately 3 times more common in women than in men.

• Neurologic - Female-to-male ratio approximately 3.5:1
• Venous - More common in males than in females
• Arterial - No sexual predilection

Age

The onset of symptoms usually occurs in persons aged 20-50 years.

Clinical

History

• Neurologic symptoms occur in 95% of cases. The lower 2 nerve roots of the brachial plexus, C8 and T1, are most commonly (90%) involved, producing pain and paresthesias in the ulnar nerve distribution.
• The second most common anatomic pattern involves the upper 3 nerve roots of the brachial plexus, C5, C6, and C7, with symptoms referred to the neck, ear, upper chest, upper back, and outer arm in the radial nerve distribution.
• Neurologic
  • Pain, particularly in the medial aspect of the arm, forearm, and the ring and small digits
  • Paresthesias, often nocturnal, awakening the patient with pain or numbness
  • Loss of dexterity
  • Cold intolerance
  • Occipital headache
  • Weakness
  • Raynaud phenomenon, hand coldness, and color changes may also be seen, usually due to an overactive sympathetic nervous system as opposed to ischemia.
  • Most have a history of neck trauma preceding their symptoms, most commonly from auto accidents and repetitive stress at work.
• Venous - Pain, often in younger men and often preceded by excessive activity in the arms
  • Swelling of the arm
  • Cyanosis
  • Paresthesias in the fingers and hand (may be secondary to swelling as opposed to nerve compression)
• Arterial
  • Pain
  • Claudication
  • Pallor
  • Coldness
  • Paresthesias
  • Often in young adults with a history of vigorous arm activity
  • Symptoms usually develop spontaneously from arterial emboli.

Physical

In most cases, the physical examination findings are completely normal. Other times, the examination is difficult because the patient may guard the extremity and exhibit giveaway-type weakness. The sensory examination is often unreliable.

• Provocative tests, such as the Adson, costoclavicular, and hyperabduction maneuvers, are unreliable. Approximately 92% of asymptomatic patients have variation in the strength of the radial pulse during positional changes.
• The elevated arm stress test (EAST) is of debatable use, but it may be the most reliable screening test. It evaluates all 3 types of thoracic outlet syndrome (TOS).
  • To perform this test, the patient sits with the arms abducted 90 degrees from the thorax and the elbows flexed 90 degrees. The patient then opens and closes the hands for 3 minutes.
  • Patients with TOS cannot continue this for 3 minutes because of reproduction of symptoms. Patients with carpal tunnel syndrome experience dysesthesias in the fingers, but do not have shoulder or arm pain.
• Neurologic
  • A typical patient is a young, thin female with a long neck and dropping shoulders.
  • A positive EAST result and the presence of a radial pulse are strong indicators of neurologic involvement of the brachial plexus.
  • Supraclavicular tenderness may be present.
  • Usually, no evidence of muscle atrophy is present, although the classic finding is known as the Gilliatt-Sumner hand, with the most dramatic atrophy in the abductor pollicis brevis, with lesser involvement of the interossei and hypothenar muscles.
  • Paresthesias/sensory loss is restricted to the ulnar aspect of the hand and forearm.
  • Weakness (usually subtle) of affected limb may be noted.
• Venous
  • Edema of the upper extremity
  • Cyanosis of the upper extremity
  • Distended superficial veins of the shoulder and chest
• Arterial
  • Pallor and pulselessness
  • Coolness on the affected upper extremity
  • Lower blood pressure in affected arm of greater than 20 mm Hg (a reliable indicator of arterial involvement)
  • Rarely can produce multiple small infarcts on the hand and fingers (embolization)

Causes

The 3 major causes of TOS are anatomic, trauma/repetitive activities, and neurovascular entrapment at the costoclavicular space.

• Anatomic
  • Scalene triangle: Anterior scalene muscle frontally, middle scalene muscle posteriorly, and the upper border of the first rib inferiorly account for most cases of neurologic and arterial TOS.
  • Cervical ribs are found in most arterial cases but rarely in venous and neurologic cases.
  • Congenital fibromuscular bands are noted in as many as 80% of patients with neurologic TOS.
  • Transverse process of C7 is elongated.
• Trauma or repetitive activities
  • Motor vehicle accident hyperextension injury, with subsequent fibrosis and scarring
  • Effort vein thrombosis (ie, spontaneous thrombosis of the axillary veins following vigorous arm exertion)
  • Playing a musical instrument: Musicians can be particularly susceptible owing to their need to maintain the shoulder in abduction or extension for long periods.
• Neurovascular entrapment: This occurs in the costoclavicular space between the first rib and the head of the clavicle.

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