eMedicine Specialties > Sports Medicine > Spine

Thoracic Outlet Syndrome

Author: Daryl A Rosenbaum, MD, Assistant Professor, Director of Sports Medicine Fellowship, Department of Family and Community Medicine, Wake Forest University School of Medicine; Team Physician, United States Soccer Federation
Coauthor(s): Matthew L Silvis, MD, Assistant Professor, Departments of Family and Community Medicine and Orthopedics and Rehabilitation, Pennsylvania State University College of Medicine; Ajay Kalra, MD, Consulting Surgeon, Surgical Specialists; Matt Thornburg, MD, Staff Physician, Department of Family and Community Medicine, University of Missouri Health Care at Columbia; Donald Spadone, MD, Assistant Professor, Department of Surgery, Division of Vascular Surgery, University of Missouri Health Sciences Center
Contributor Information and Disclosures

Updated: Aug 15, 2008

Introduction

Background

Thoracic outlet syndrome is not the name of a single entity, but rather a collective title for a variety of conditions attributed to compression of these neurovascular structures as they traverse the thoracic outlet.^1,2,3,4 The thoracic outlet is bordered by the scalene muscles, first rib, and clavicle. Neurovascular structures pass from the neck and thorax into the axilla through this space. Thoracic outlet syndrome remains one of the most controversial clinical entities in medicine.^5,6,7

For excellent patient education resources, visit eMedicine's Hand, Wrist, Elbow, and Shoulder Center. Also, see eMedicine's patient education articles Shoulder and Neck Pain and Electromyography (EMG).

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Frequency

United States

The wide variability of symptoms and signs in patients with thoracic outlet syndrome and the lack of an objective confirmatory test for the diagnosis makes correctly identifying patients with thoracic outlet syndrome difficult.⁸ Therefore, determining its exact incidence remains elusive; estimates range from 3-80 cases per 1000 population.⁹ Thoracic outlet syndrome is more common in women, particularly those with poor muscular development, poor posture, or both.¹⁰

Functional Anatomy

The neurovascular bundle courses through 3 spaces, or triangles, as it exits the neck to reach the axilla and proximal arm. All 3 spaces can be the source of compression of the various components of the neurovascular bundle, including the brachial plexus and the subclavian vessels.¹¹ These spaces are small at rest and become even smaller with certain arm maneuvers, such as abduction and external rotation.^12,13 This can aid in the diagnosis of thoracic outlet syndrome and forms the basis for provocative testing, which is discussed later (see Clinical, Physical).
 
The first space is the interscalene triangle. It is bordered by the anterior scalene muscle, the middle scalene muscle, and the upper border of the first rib. This space contains the trunks of the brachial plexus and subclavian artery. The interscalene triangle is the most common site for neural compression, vascular compression, or both.⁹  

The second space is the costoclavicular triangle, which is bordered by the clavicle, first rib, and scapula and contains the subclavian artery and vein and the brachial nerves.
 
The third and final space is beneath the coracoid process just deep to the pectoralis minor tendon; it is referred to as the subcoracoid space.

Sport-Specific Biomechanics

Thoracic outlet syndrome is most often seen in patients who engage in repetitive motions that place the shoulder at the extreme of abduction and external rotation. An example of such activity is swimming, especially with the freestyle stroke, butterfly stroke, and backstroke. When a swimmer reports tightness and pain around the shoulder, neck, and clavicle as his or her hand enters the water, thoracic outlet syndrome should be suspected.

In addition to swimmers, other athletes affected by thoracic outlet syndrome include water polo, baseball, and tennis players and athletes in any other activity that places repetitive stress on the shoulder at the extremes of abduction and external rotation. These individuals may present with neurologic and arterial or venous symptoms. Venous thoracic outlet syndrome most commonly develops in young male athletes in whom the upper extremity musculature is overdeveloped as a result of work or physical conditioning. Baseball players, whose sport requires repetitive throwing motions, are at increased risk for arterial thoracic outlet syndrome in their dominant arm.

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Clinical

History

The initial presentation of thoracic outlet syndrome is dependent on whether the compression is primarily vascular, neurogenic, or a combination of both. It is also dependent on the underlying continuum of histopathologic changes noted with chronic nerve compression, ranging from intermittent to constant debilitating symptoms.¹⁴  Three symptomatic patterns emerge; these are vascular, true neurogenic, and disputed or nonspecific-type thoracic outlet syndrome.

Vascular thoracic outlet syndrome is rare and can involve the subclavian artery or vein. Both forms of vascular thoracic outlet syndrome tend to occur in young patients who perform vigorous overhead arm activity such as throwing. With venous obstruction (if secondary to thrombosis, Paget-von Schrötter syndrome), patients may present with upper extremity swelling, venous distention, or diffuse arm or hand pain (including the forearm).^14,15

With arterial obstruction, patients may report color changes of their affected upper extremity, claudication, or diffuse arm or hand pain (including the forearm). Because of arterial collateral blood flow, the iinitial symptoms tend to be mild, with arm ache and fatigue, particularly after overhead activity. Patients typically seek medical evaluation after ischemic events (eg, ulceration, gangrene, absent pulses) occur.¹⁴

Neurogenic thoracic outlet syndrome involves compression of the brachial plexus. Similar to vascular thoracic outlet syndrome, a pure neurogenic presentation is also rare. Patients present with painless atrophy of the intrinsic muscles of the hand, and athletes may report difficulty grasping a racket or ball as a result of intrinsic muscle weakness. They may also report sensory loss or paresthesias. Pain is often reported but is not as dramatic as in the nonspecific-type thoracic outlet syndrome.⁹ Again, neurogenic thoracic outlet syndrome tends to affect individuals who perform overhead arm activities.

The disputed or nonspecific-type thoracic outlet syndrome refers to a large group of patients with unexplained pain in the arm, scapular region, and cervical region. Typically, their symptoms begin after a traumatic event (eg, motor vehicle accident). Much debate surrounds this diagnosis, with certain providers believing the disorder is underdiagnosed.⁶ and others believing it is overdiagnosed.⁷

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Physical

The examination should begin with an assessment of the patient’s posture. A slumped posture of the shoulders and upper back and a “poked-forward” position of the head and neck are comfortable but potentially damaging for the scapular and neck muscles and are thought to contribute to the susceptibility for thoracic outlet syndrome.¹⁴
 
The symmetry of both arms should be evaluated. Cervical active range-of-motion assessment and the Spurling test (ie, patient’s head is placed in extension and lateral flexion, with axial compression applied by the examiner to the patient’s head in an effort to recreate radicular pain) should be performed. Active and passive range of motion of both shoulders should be examined. A careful neurovascular examination of both upper extremities is needed, taking care to remember that the muscles and nerves supplied by the lower brachial plexus are most commonly affected.    
 
Vascular thoracic outlet syndrome has different examination signs depending on whether the venous or arterial vessels are affected. With venous compression, patients often present with edema and cyanosis of the upper extremity. They may also have distended veins in the shoulder or chest. With arterial compression, patients often present with pallor, a weak or absent pulse, and coolness of the upper extremity. Decreased blood pressure greater than 20 mm Hg in the affected arm compared with the contralateral arm is sometimes noted and is a reliable indicator of arterial involvement.⁹ Rarely, small infarcts are noted in the hands and fingers, which are due to embolization.
 
The classic finding in a person with neurogenic thoracic outlet syndrome is the Gilliatt-Sumner hand. This physical examination finding includes atrophy of the abductor pollicis brevis with lesser involvement of the interossei and hypothenar muscles.⁹ Patients may also have decreased sensation that follows the ulnar nerve distribution because the lower trunks of the brachial plexus are usually more involved than the upper trunks.    
 
Patients with disputed or nonspecific-type thoracic outlet syndrome tend to have diffuse upper extremity pain with guarding. Examination tends to be difficult and findings nonfocal. Weakness and decreased sensation tend to be unreliable signs that are difficult to quantify. 

Because of the variability of the structures involved in thoracic outlet syndrome, many provocative maneuvers have been described to aid in diagnosis. They include the Adson maneuver, Wright test, and Roos stress test.^10,14  Note, however, that these tests have high rates of false-positive and false-negative results.¹⁴

The Adson maneuver is performed by positioning the tested shoulder in slight abduction and extension. Then, the patient extends his or her neck and turns the head toward this affected shoulder. The patient inhales while the examiner simultaneously palpates the ipsilateral radial pulse. If the pulse diminishes or the patient has paresthesias, the test result is considered positive as long as this maneuver does not cause symptoms on the asymptomatic contralateral side.

The Wright test is performed by progressively hyperabducting and externally rotating the patient’s affected arm while assessing the ipsilateral radial pulse. Again, the test result is considered positive if the pulse diminishes or paresthesias develop.¹⁰

The Roos stress test is performed with the patient positioning both of his or her shoulders in abduction and external rotation of 90° with elbow flexion at 90°. The patient then opens and closes his or her hands for several minutes. Reproduction of symptoms or a sensation of heaviness or fatigue is considered a positive test result.¹⁰  

Causes

Causes of thoracic outlet syndrome can be divided into bony and soft-tissue factors. Bony factors include abnormalities such as anomalous cervical ribs, hypoplastic first thoracic ribs, and exostoses of the first rib or clavicle.^16,17 The rate of anomalous cervical ribs is considered to be 0.17-0.74% in the general population, and the rate of rudimentary first ribs is 0.29-0.76%.¹⁴  

Soft-tissue factors include congenital anomalies such as anomalous fibrous muscular bands near the brachial plexus and hypertrophic muscles in athletes and weight lifters.^17,18 Space-occupying lesions (eg, tumors, cysts) and inflammatory processes also occur in the soft tissues and can cause thoracic outlet syndrome. 
 
Trauma or mechanical stress to the neck, shoulders, or upper extremities can lead to thoracic outlet syndrome. In fact, a combination of neck trauma and anatomic predisposition (ie, cervical rib) is considered the main etiology of thoracic outlet syndrome. Posttraumatic conditions such as hematoma, myositis ossificans, and scar formation can be important variables, as can a droopy shoulder secondary to trapezius muscle weakness.¹⁹ Thoracic outlet syndrome can be secondary to malunion of a clavicle fracture.²⁰

Interestingly, multiple points of compression may be present as the peripheral nerves descend from the thoracic outlet to the hand (simultaneous thoracic outlet syndrome and ulnar nerve compression at the elbow or carpal tunnel syndrome in the wrist). This has been referred to as double-²¹ or multiple-crush syndrome.²²

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