Thoracic Outlet Syndrome

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.[10, 11]  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%.[12]

Soft-tissue factors include congenital anomalies such as anomalous fibrous muscular bands near the brachial plexus and hypertrophic muscles in athletes and weight lifters.[11, 13]  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.[14]  Posttraumatic conditions such as hematoma, myositis ossificans, and scar formation can be important variables, as can a droopy shoulder secondary to trapezius muscle weakness.[15]  Thoracic outlet syndrome can be secondary to malunion of a clavicle fracture.[16]

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-[17]  or multiple-crush syndrome.[18]

United States statistics

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.[19] Therefore, determining its exact incidence remains elusive; estimates range from 3-80 cases per 1000 population.[20]

Sex- and age-related demographics

Thoracic outlet syndrome is more common in women, particularly those with poor muscular development, poor posture, or both.[21]

The onset of symptoms typically occurs in persons aged 20-50 years. Although thoracic outlet syndrome is uncommon in children, cases have been reported in adolescents.[22]

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.[23] These spaces are small at rest and become even smaller with certain arm maneuvers, such as abduction and external rotation.[24, 25] 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.[20]

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.

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.

Symptoms resolve with conservative therapy in approximately 90% of individuals. Postsurgical success rates over 1 year vary from 43-78%. A good surgical result means improvement, not total cure. Most patients are able to return to their previous lifestyle without difficulty. Job modification is required in individuals who perform repetitive activities, work on assembly lines, perform heavy laboring, or work with their arms elevated.

A systematic review by Garraud et al found that the prognosis for thoracic outlet syndrome in athletes appeared to be generally better than the prognosis in the general population, possibly because of better physical condition and younger age.[26]

Complications

Ischemic changes, including gangrene, are potential complications of arterial thoracic outlet syndrome. Pulmonary embolism is reported in 0-28.5% of patients with subclavian-axillary venous thrombosis. Venous gangrene and upper extremity phlegmasia cerulea dolens account for 2-5% of all cases of phlegmasia. Nerve injury (eg, brachial plexus neurapraxia) is the most serious postoperative complication after thoracic outlet decompression. Bleeding problems from the subclavian vessels and lymph leakage from the thoracic duct occur infrequently.

Inform patients that symptoms recur in 15-20% of patients.[27]  The initial treatment is conservative in nature and includes a search for other diagnoses (see Differentials and Other Problems to Be Considered). Chronic pain may improve with the continued use of analgesics and a routine exercise and strengthening program.

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.[12] 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).[12, 28]

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 initial 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.[12]

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.[20] 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,[8] and others believing it is overdiagnosed.[9]

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.[12]

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.[20]  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.[20]  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.[21, 12]  Note, however, that these tests have high rates of false-positive and false-negative results.[12]

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.[21]

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.[21]

In thoracic outlet syndrome with vascular compromise or nerve compression, with resultant atrophy of the intrinsic hand muscles, the diagnosis is not controversial and specific tests can confirm the diagnosis. However, no infallible clinical tests, laboratory tests, radiographic tests, or electrical studies establish the diagnosis of thoracic outlet syndrome syndrome in patients with disputed or nonspecific-type thoracic outlet syndrome.[29] Many tests are available to refine the differential diagnosis and confirm or exclude other potential conditions (see Differentials and Other Problems to Be Considered).

To exclude systemic disease and inflammation, a few simple blood tests may refine the differential diagnosis for thoracic outlet syndrome, including a blood glucose level, complete blood cell (CBC) count, erythrocyte sedimentation rate (ESR), basic metabolic panel, thyrotropin level, and rheumatologic workup, if indicated.

Radiography

Cervical spine and upper thoracic spine radiographs may demonstrate bony abnormalities. Chest, shoulder, and clavicle radiographs may also identify bony abnormalities.

Computed tomography (CT) scanning and magnetic resonance imaging (MRI)

CT scanning and MRI are more useful for identifying other conditions that might cause similar symptoms, rather than for establishing the diagnosis of thoracic outlet syndrome.[30]

Magnetic resonance angiography (MRA)

MRA can be useful for the diagnosis of arterial vascular thoracic outlet syndrome.[31, 32]

Venography and duplex scanning

Venography and duplex scanning (ie, ultrasonography combined with Doppler velocity waveforms) are used to assist in the diagnosis of subclavian vein compression (thrombosis). These tests can be performed dynamically with positions that recreate the tension placed on the thoracic outlet during certain motions such as abduction and external rotation.

Electrodiagnostic studies can be helpful for classic cases of neurogenic thoracic outlet syndrome and therefore can be useful when the results are positive. However, many symptoms are intermittent in neurogenic thoracic outlet syndrome; therefore, negative test results do not rule out this diagnosis. Electrodiagnostic testing can also be helpful in diagnosing other neuromuscular disorders.

Nerve conduction velocity has been used for the diagnosis of thoracic outlet syndrome as defined by a reduction to less than 85 m/s of either the ulnar or median nerves across the thoracic outlet and was found to corroborate the clinical diagnosis. A nerve conduction velocity of less than 60 m/s was considered an indication for surgery.[18] However, as with many aspects of thoracic outlet syndrome, this remains controversial and has not been universally accepted.

Somatosensory evoked potentials are equally controversial, with some studies favoring their use[33] and others not.[34]

Electromyography may be helpful in confirming the presence or absence of a specific alternative diagnosis.

A study reported that intravascular ultrasound detected greater levels of stenosis than venography in the treatment of 14 venous thoracic outlet syndrome patients.[35]

 

Rehabilitation Program

Surgery in cases of thoracic outlet syndrome is indicated for acute vascular insufficiency and progressive neurologic dysfunction. For subclavian venous thrombosis, treatment addresses 3 problems: the clot, the extrinsic compression, and the intrinsic damage to the vein.[36, 37] Thrombolysis with urokinase is the most commonly recommended treatment, with continued anticoagulation for several months. The timing of surgical decompression is debated, but surgical decompression is needed for long-term improvement.[18, 38, 39] Patients with acute ischemia of the upper extremity require prompt diagnosis and surgical treatment.[40]

All other patients should receive nonoperative treatment that includes relative rest, nonsteroidal anti-inflammatory medications (NSAIDs), cervicoscapular strengthening exercises, and modalities such as ultrasound, transcutaneous nerve stimulation, and biofeedback. Conservative care has been shown to be successful in most patients.[41, 42] In those patients in whom pain is refractory to conservative care, surgery should be considered.

Physical therapy

Physical therapy that addresses postural abnormalities and muscle imbalance relieves symptoms in most patients with thoracic outlet syndrome by relieving pressure on the thoracic outlet. This is based on 3 potential effects of abnormal static or repetitive postures and positions.

First, increased pressure directly around nerves at various entrapment points or increased tension on nerves creates chronic nerve compression. Second, certain postures maintain muscles in abnormally shortened positions, resulting in a new length. When these adapted muscles are stretched, pain occurs. Third, abnormal posture results in some muscles being stretched and others being shortened to new lengths, resulting in both being placed at a mechanical disadvantage and leading to muscle imbalance.[12] This is the basis for physical therapy.

Although, many conservative protocols for physical therapy are described, few outcome studies have been published. The few studies available demonstrate positive outcomes for most patients.[43, 44, 45]

Patient treatment includes several components that address the brachial plexus nerve compression and muscle imbalance in the cervicoscapular region. Key points emphasized in treatment begin with education. Postural correction focuses on positions of most risk and least risk for compression, with integration into the patient's activities of daily living at work, home, and sleep. For example, patients should avoid overhead arm positions while sleeping. Postural and position correction can be aided by wrist splints, elbow pads, soft neck rolls for nighttime use, and lumbar supports for sitting. In addition, the impact of body habitus and general physical conditioning should be evaluated and discussed (ie, obesity, breast hypertrophy).

Physiotherapy focuses on pain control and range of motion with specific stretching exercises. Stretching should begin with short, tight muscles (ie, upper trapezius, levator scapulae, scalenes, sternocleidomastoid, pectoralis major, pectoralis minor, suboccipitalis) and should not be aggressive. Once pain control and cervical motion are regained, strengthening exercises of the lower scapular stabilizers are begun, as is an aerobic conditioning program.[45, 46] The importance of patient compliance should not be overlooked.

Surgical Intervention

Little argument exists against the surgical treatment of a patient with severe compression or compromise of the subclavian vein or artery.[19, 24, 25, 37, 47] Likewise, patients with atrophy of the intrinsic muscles of the hand secondary to thoracic outlet syndrome with no distal sites of compression need surgical intervention.[12]  However, less severe cases are more controversial.

Because of the high prevalence of surgical complications and variable reports of success, many surgeons offer surgery to patients with disputed or nonspecific-type thoracic outlet syndrome only as a last resort after prolonged conservative management and a detailed discussion regarding the risks and complications of surgery. Potential complications from surgery can include pneumothorax, injury to the subclavian artery or vein, injury to the brachial plexus and long thoracic nerve, apical hematoma, intercostobrachial nerve injury, and injury to the thoracic duct.[48]

The surgical approach used varies and may be specialty dependent, with the transaxillary approach preferred by many thoracic and vascular surgeons and the anterior supraclavicular approach favored by most neurosurgeons.[20, 49] Both approaches allow for supraclavicular decompression, which consists of first rib (and cervical rib if present) removal and part or total scalene muscle removal. In a study of 33 patients with venous thoracic outlet syndrome, Siracuse et al reported good results with an infraclavicular surgical approach.[50]

For neurogenic thoracic outlet syndrome with examination findings of tenderness or reproduction of symptoms on palpation of the coracoid space only, isolated pectoralis minor tenotomy may be sufficient.[51]

Success rates for surgery vary dramatically in the literature. One review of 47 patients with thoracic outlet syndrome revealed 75% lower plexus and 50% upper plexus compressions remained asymptomatic at 4.6 years.[52] Morbidity in this study involved 17% of patients and was most frequently the result of incisional pain.

A literature review by Peek et al found evidence that most patients who undergo surgery for thoracic outlet syndrome benefit from the treatment. The investigators reported that postoperatively, 90% of the study's patients with arterial or venous thoracic outlet syndrome improved under Derkash’s classification to an excellent/good rating, while patients with neurogenic thoracic outlet syndrome showed a 28.3-point improvement in their Disabilities of the Arm, Shoulder and Hand scores.[53]

However, not all studies have been so impressive. One retrospective analysis of patients with nonspecific neurogenic thoracic outlet syndrome demonstrated work disability at 1 year after surgery in 60% of patients. At 4.8 years of follow-up, 72.5% patients were limited in activities.[54]

This has led many surgeons to agree with Wood et al, who empathically stated in 1988 that some errors always occur in diagnosis, and, therefore, surgery should be advised "on a basis of exclusion and with great reservation."[29] This is especially true for disputed or nonspecific-type thoracic outlet syndrome.[20]

A study that evaluated the outcomes of patients who underwent first rib resection (FRR) for all 3 forms of thoracic outlet syndrome (TOS) during a period of 10 years reported that excellent results were seen in this surgical series of neurogenic, venous, and arterial TOS due to appropriate selection of neurogenic patients, use of a standard protocol for venous patients, and expedient intervention in arterial patients.[55]

Consultations

Consultation with a sports medicine specialist and surgeon is recommended.

Other Treatment

Injection of botulinum toxin into the muscles of the thoracic outlet (scalenes, pectoralis minor, subclavius) has potential for obtaining long-term symptom relief, but further research is needed.[56]

A 2014 Cochrane review looked to evaluate outcome studies of treatments of TOS that took place at a minimum of 6 months after the intervention.[57] The review found that there was very low quality evidence that transaxillary first rib resection decreased pain more than supraclavicular neuroplasty, and found no randomized evidence that either treatments is better than no treatment at all. The review also reported that there is moderate evidence to suggest that treatment with botulinum toxin injections yielded no great improvements over placebo injections of saline. There is no evidence from randomized controlled trials for the use of other currently used treatments. The review concluded that there is a need for an agreed definition for the diagnosis of TOS, agreed outcome measures, and high quality randomized trials that compare the outcome of interventions with no treatment and with each other.[57]

Rehabilitation Program

Physical therapy

Postoperative physical therapy is essential for strengthening and range of motion.

Rehabilitation Program

Physical therapy

Continued regular stretching of the muscles around the cervical girdle (eg, scalene, pectoralis major and minor, trapezius, levator scapulae, and sternocleidomastoid muscles) is essential.

Recommended exercises for thoracic outlet syndrome include neck stretching, abdominal breathing, and postural exercises. Ineffective therapies include shoulder shrugs (useful for prevention), weight lifting, and neck traction. Exercises should be performed at home at least twice a day.

Medical Issues/Complications

Patients may require continued postoperative anticoagulation with warfarin.

To help prevent recurrence of thoracic outlet syndrome, the patient should avoid sleeping with his or her arms in an overhead position.

Return to play following treatment of thoracic outlet syndrome is difficult to generalize and depends on multiple variables, including the type of thoracic outlet syndrome, the presence of contributing factors, the treatment plan, the response to treatment, and the sport played.

A retrospective review by Talutis et al, which included 60 adolescent athletes, found that about 94% of the patients with venous thoracic outlet syndrome were able to return to play after operative decompression, compared with nearly 74% of those with neurogenic thoracic outlet syndrome. Of the patients with neurogenic thoracic outlet syndrome, 10% had other injuries and 5% had medical disorders that prevented their return to play.[58]

The patient should avoid repetitive motions, stressful lifting, and overhead work. Performing a regular exercise program for improving flexibility and strength is beneficial. Shoulder-elevating movements (eg, shrugs, hand circles) increase range of motion and aid in prevention, but they are not a treatment modality.

Acute findings of ischemia or thrombosis require immediate evaluation and anticoagulation.

Class Summary

Anticoagulants are used to treat acute arterial or venous occlusion.

Heparin

Potentiates antithrombin III and prevents conversion of fibrinogen to fibrin. Inhibits thrombogenesis.

Warfarin (Coumadin)

Interferes with hepatic synthesis of vitamin K–dependent coagulation factors. Tailor dose to maintain an INR in the range of 2-3.

Class Summary

The use of analgesics may aid in relieving the discomfort of an acute occlusion of the vascular structures or nervous impingement.

Acetaminophen (Tylenol, Feverall, Aspirin Free Anacin)

DOC for pain in patients with documented hypersensitivity to aspirin or NSAIDs, those with upper GI disease, and those who are taking oral anticoagulants.

Ibuprofen (Motrin, Ibuprin)

DOC for patients with mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Acetaminophen and codeine (Tylenol #3)

Oral analgesic indicated for treatment of moderate pain.

Class Summary

Thrombolytics are used to promote fibrinolysis of intraluminal thrombus or embolus in occluded vessels.

Urokinase (Activase)

Direct plasminogen activator that acts on endogenous fibrinolytic system and converts plasminogen to the enzyme plasmin, which, in turn, degrades fibrin clots, fibrinogen, and other plasma proteins. The advantage is that the agent is nonantigenic.

Most often used for local fibrinolysis of thrombosed catheters and superficial vessels. When used for local fibrinolysis, urokinase is given as local infusion directly into the area of thrombus and with no bolus given.

The dose should be adjusted to achieve clot lysis or patency of the affected vessel.