Thoracic Outlet Syndrome in Emergency Medicine

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 that results in upper extremity symptoms. 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 such that TOS is usually classified into neurogenic, venous, and arterial forms.[1] Most presentations to the emergency department (ED) are nonemergent and require only symptomatic treatment and referral.

The brachial plexus trunks and subclavian vessels are subject to compression or irritation as they course through three 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 thoracic outlet syndrome (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.

Common etiologies for each anatomic form of thoracic outlet syndrome (TOS) include the following:

• Neurogenic TOS: Etiology is most often a hyperextension neck injury, such as whiplash after a motor vehicle accident or a fall.[2] Other causes include repetitive injury most often form sitting at a keyboard for long hours.

• Venous TOS: Etiology is obstruction of the subclavian vein, either thrombotic or nonthrombotic.[2] The cause is a combination of predisposing and precipitating factors. The predisposition is congenital anatomic narrowing at the point where the subclavian and jugular veins join to form the innominate vein. The precipitating factor that leads to thrombosis is excessive activity of the arm such as throwing a baseball, swimming, weight lifting, or working with the arms elevated. Coagulopathies can also be a precipitating cause.

• Arterial TOS: Etiology is subclavian artery stenosis or aneurysm with thrombus formation and distal emboli usually due to a cervical rib or anomalous first rib.[2] The aneurysm and stenosis are usually asymptomatic until embolization occurs.

United States data

Because no objective confirmatory test is available for thoracic outlet syndrome (TOS), there is much disagreement with regards to its true incidence. Reported figures range from 3-80 cases per 1000 people.[3, 4]

Sex- and age-related demographics

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

• Neurologic - Female-to-male ratio approximately 3.5:1

• Venous - More common in males than in females

• Arterial - No gender predilection

The onset of symptoms usually occurs in persons aged 20-50 years. Although infrequent, TOS has been reported in adolescents.[5]

Neurologic thoracic outlet syndrome (TOS) is generally neither progressive nor likely to resolve spontaneously.

Arterial or venous TOS usually has a good outcome with adequate treatment.

Complications

Neurologic complications include chronic pain.

Arterial complications include thrombosis, thromboembolism, acute ischemia, and poststenotic aneurysm formation.

Venous thrombosis may develop.

Neurologic symptoms occur in 95% of cases of thoracic outlet syndrome (TOS). The lower two nerve roots of the brachial plexus, C8 and T1, are most commonly (90%) involved, producing pain and paresthesia in the ulnar nerve distribution.

The second most common anatomic pattern involves the upper three 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 TOS (NTOS)

Most patients have a history of neck trauma preceding their symptoms, most commonly from auto accidents and repetitive stress at work. Symptoms of neurologic TOS (NTOS) are most often those of nerve irritation and include the following:

• Pain, particularly in the medial aspect of the arm, forearm, and the ring and small digits

• Paresthesia, often nocturnal, awakening the patient with pain or numbness. Most often involves all five fingers but usually is most noticeable in the fourth and fifth fingers and the ulnar forearm.

• Weakness

• Cold intolerance

• Neck pain, pain over the trapezium, anterior chest wall pain, and occipital headache may also occur.

• Raynaud phenomenon, hand coldness, and color changes may also be seen, usually due to an overactive sympathetic nervous system as opposed to ischemia.

Venous TOS

Venous TOS (VTOS) is most often seen in younger men and presents with pain, often preceded by excessive activity in the arms. Symptoms of VTOS are those of an obstructed vein and include the following:

• Swelling of the arm

• Cyanosis

• Paresthesias in the fingers and hand (may be secondary to swelling as opposed to nerve compression)

Arterial TOS

Arterial TOS (ATOS) is often in young adults with a history of vigorous arm activity. Symptoms are those of digital and hand ischemia, and usually develop spontaneously from arterial emboli. Symptoms of ATOS include the following:

• Pain

• Pallor

• Coldness

• Paresthesias

In most cases, the physical examination findings of thoracic outlet syndrome (TOS) 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 testing

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.

Elevated arm stress test

The elevated arm stress test (EAST) is of debatable use, but it may be the most reliable screening test. It evaluates all three types of 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 dysesthesia in the fingers, but do not have shoulder or arm pain.

Upper limb tension test of Elvey

The upper limb tension test of Elvey may be helpful. This test serially puts tension on the brachial plexus similar to straight leg raising in the lower extremity.

Neurologic evaluation

Findings in the neurologic evaluation include the following:

• A typical patient is a young, thin female with a long neck and drooping shoulders.

• A positive EAST test 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.

• Paresthesia/sensory loss is restricted to the ulnar aspect of the hand and forearm.

• Weakness (usually subtle) of the affected limb may be noted.

Venous evaluation

Findings in the venous evaluation include the following:

• Edema of the upper extremity

• Cyanosis of the upper extremity

• Distended superficial veins of the shoulder and chest

Arterial evaluation

Findings in the arterial evaluation include the following:

• Pallor and pulselessness

• Coolness of the affected upper extremity

• Lower blood pressure in affected arm of greater than 20 mm Hg (a reliable indicator of arterial involvement)

• Multiple small infarcts on the hand and fingers (embolization) (rarely)

With the rare exception of a vascular cause, the vast majority of emergency department presentations of thoracic outlet syndrome are not emergent. Screening tests may be appropriate if indicated and to rule out other causes. Once the clinical diagnosis is made, most of the imaging studies and other tests should be reserved for the outpatient setting.

The noninvasive imaging modality of choice in evaluating patients with suspected thoracic outlet syndrome (TOS) is magnetic resonance imaging (MRI). However, computed tomography (CT) scanning plays an important role as well, especially in delineating bone anatomy.[7]

Radiography

Cervical radiography may demonstrate a skeletal abnormality[8]

Chest radiography findings may include the following:

• Cervical or first rib: This is usually associated with the arterial form of TOS but also can be a predisposition to developing the neurologic form following neck trauma.

• Clavicle deformity

• Pulmonary disease

• Pancoast tumor

Ultrasonography

Color flow duplex scanning for suspected arterial or vascular TOS may be indicated.[9]

Arteriography

Indications for arteriography include the following:

• Evidence of peripheral emboli in the upper extremity

• Suspected subclavian stenosis or aneurysm (eg, bruit or abnormal supraclavicular pulsation)

• Blood pressure differential greater than 20 mm Hg

• Obliteration of radial pulse during elevated arm stress test (EAST)

Venography

Indications for venography include the following:

• Persistent or intermittent edema of the hand or arm

• Peripheral unilateral cyanosis

• Prominent venous pattern over the arm, shoulder, or chest

The following special studies are generally appropriate in the outpatient setting; they should be arranged by the primary care physician once the patient has been discharged from the emergency department:

• Nerve conduction evaluation via root stimulation and F wave is the best direct approach to evaluation of neurologic thoracic outlet syndrome (TOS).

• Cervical myelogram, computed tomography (CT) scanning, or magnetic resonance imaging (MRI) may be appropriate for patients suspected of having cervical disk disease or spinal cord disease.

Electromyography (EMG) is unreliable and does not provide objective evidence of TOS.

A Cochrane review concluded that despite many reports on conservative and surgical intervention, complications, outcomes, and success rates, rigorous scientific investigation and management is lacking.[10]

For most patients, conservative treatment for thoracic outlet syndrome (TOS) is generally recommended. Stress avoidance, work simplification, and job site modification are also recommended to avoid sustained contraction and repetitive or overhead work that exacerbate symptoms.

Myofascial or chronic pain elements can be addressed through exercise programs, good posture, and self-management.

The potential outlet space can be maximized through a program of stretching and strengthening of the shoulder-elevating mechanism, such as with the following:

• Trapezius and rhomboid strengthening (eg, shoulder shrugs and bilateral shoulder retraction while standing or lying prone)

• Shoulder mobilization (eg, hand circles and standing corner pushups)

• Postural exercises (eg, cervical and lumbar spine extension)

Most presentations of thoracic outlet syndrome (TOS) to the ED are nonemergent and require only symptomatic treatment and referral. Vascular TOS, although much less common than neurologic TOS, requires more urgent care.

Management of vascular (arterial and venous) TOS includes the following:

• Immediate heparinization

• Vascular surgery consultation

• Color flow duplex scanning

• Angiography or venography

Neurologic TOS is generally managed with conservative outpatient physiotherapy.

Hospitalization

Patients with vascular TOS may be admitted for the following:

• Angiography or venography

• Color flow duplex scanning

• Catheter-directed local infusion of thrombolytic agent

• Thrombectomy (for total thrombotic obstruction)

• Fogarty catheter embolectomy

• Emergent or urgent surgical exploration

Operative therapy is indicated for neurologic TOS if conservative approach fails.[11]

Supraclavicular decompression techniques may include anterior and middle scalenectomy, excision of a cervical rib if present and first rib resection.[1, 12]

Using a prospectively maintained database, Orlando et al. retrospectively evaluated the outcomes of 538 patients who underwent first rib resection (FRR) for indications of neurogenic, venous, and arterial TOS from August 2003 through July 2013. A comparison of the second 5-year period with the first 5-year period showed that improved or fully resolved symptoms increased from 93% to 96%. The mean length of stay was 1 day.[13]

A retrospective survey of 158 workers' compensation patients undergoing surgery for TOS showed that 60% were still work-disabled 1 year after surgery.[14]

Consultations

Neurologic, orthopedic, or vascular surgery consultation(s) may be indicated depending on the type of pathologic condition.

Physical medicine and rehabilitation physicians are needed for outpatient workup.

Transfer

For patients with vascular TOS, transfer to a center with experience in such cases for definitive diagnosis and treatment is indicated if it is unavailable at the current institution.

In patients with evidence of arterial or venous involvement (ischemia or thrombosis), immediate heparinization is indicated in the treatment of thoracic outlet syndrome (TOS).

Anticoagulate with warfarin for a minimum of 3 months for vascular TOS.

Analgesics are seldom helpful except to assist in the institution of a progressive exercise program.

A short-monitored course with tricyclic antidepressants may be helpful if the time course and symptoms suggest a protracted pain syndrome.

Class Summary

These agents prevent recurrent or ongoing thromboembolic occlusion of the vertebrobasilar circulation.

Heparin

Augments activity of antithrombin III and prevents conversion of fibrinogen to fibrin. Does not actively lyse but is able to inhibit further thrombogenesis. Prevents re-accumulation of clot after spontaneous fibrinolysis.

Warfarin (Coumadin)

Interferes with hepatic synthesis of vitamin K–dependent coagulation factors. Used for prophylaxis and treatment of venous thrombosis, pulmonary embolism, and thromboembolic disorders. Tailor dose to maintain INR in range of 2-3. Infants may require doses at, or near, high end of range.

Class Summary

If analgesic treatment is ineffective, a short, monitored course of TCAs can be helpful if the time course and symptoms suggest a protracted pain syndrome. The primary care physician or neurologist (not the ED physician) should be the one to prescribe such therapy.

Doxepin (Sinequan, Adapin, Zonalon)

Inhibits histamine and acetylcholine activity and has proven useful in treatment of various forms of depression associated with chronic and neuropathic pain.

Class Summary

Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and enables physical therapy regimens. Many analgesics have sedating properties, which are beneficial for patients who have sustained injuries.

Acetaminophen (Tylenol, Aspirin Free Anacin, Feverall)

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

Acetaminophen and codeine (Tylenol with codeine)

Drug combination indicated for treatment of mild to moderately severe pain.

Ibuprofen (Motrin, Ibuprin, Nuprin, Advil)

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