THORACIC OUTLET SYNDROME

Thoracic outlet syndrome (TOS) refers to compression of the neurovascular structures at the superior aperture of the thorax. The brachial plexus (95%), subclavian vein (4%), and subclavian artery (1%) are affected.

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:

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.

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

• Headache

• Venous - Pain, often in younger men and often associated with strenuous work

• Arterial

• Pain

• Claudication

• Often in young adults with a history of vigorous arm activity

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 elevated arm stress test (EAST) is 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.
• Adson's Test: With the patient in a sitting position, hands resting on thighs, the examiner palpates both radial pulses as the patient rapidly fills the lungs by deep inspiration and, with breath held, hyperextends the neck and turns the head toward the 'affected' side. If the radial pulse on that side is decidedly or completely obliterated, the result is considered positive.

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.

Imaging Studies:

• Cervical radiography - May demonstrate a skeletal abnormality

• Chest radiograph

• Cervical or first rib

• Clavicle deformity

• Pulmonary disease

• Color flow duplex scanning for suspected vascular thoracic outlet syndrome (TOS)

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.

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

Tricyclic antidepressants (TCAs) -- 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 should be the one to prescribe such therapy.

Analgesics -- 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.

• Cortisone
  Injected into a joint or muscle, cortisone can help relief and lower inflammation
• Botox injections
  Short for Botulinum Toxin A, Botox binds nerve endings and prevents the release of neurotransmitters that activate muscles. A small amount of Botox injected into the tight or spastic muscles found in TOS sufferers often provides months of relief while the muscles is temporarily paralyzed.

Further Outpatient Care:

• For most patients, conservative treatment is recommended. Stress avoidance, work simplification, and job site modification are recommended to avoid sustained contraction and repetitive or overhead work that exacerbate symptoms.

• Address myofascial or chronic pain elements through exercise programs, good posture, and self-management.
• Posture- TOS is rapidly aggravated by poor posture. Active breathing exercises and ergonomic desk setup can both help maintain active posture. Often the muscles in the back become weak due to prolonged (years) hunching. Active breathing and postural exercises are part of a program developed and advanced by Dr. Peter Edgelow of Hayward, CA.

• Maximize the potential outlet space through a program of stretching and strengthening of the shoulder-elevating mechanism.

• 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)
• Stretching- The goal of self stretching is to relieve compression in the thoracic cavity, reduce blood vessel and nerve impingement, and realign the bones, muscles, ligaments, and tendons causing the problem.
• Moving shoulders forward (hunching) then back to neutral, followed by extending them back (arching) then back to neutral, followed by lifting shoulders then back to neutral.
• Tilting and extending neck opposite to the side of injury while keeping the injured arm down or wrapped around the back.
• Ice/Heat
  Ice can be used to decrease inflammation of sore or injured muscles. Heat can also aid in relieving sore muscles by improving circulation to them. While the whole arm generally feels painful, some relief can be seen when ice/heat is applied to the thoracic region (collar bone, armpit, or shoulder blades).

This syndrome causes a compression of a large cluster of nerves, resulting in the impairment of nerves throughout the arm. By performing nerve gliding exercises one can stretch and mobilize the nerve fibers.

• Extend your injured arm with fingers directly outwards to the side. Tilt your head to the otherside, and/or turn your head to the other side. A gentle pulling feeling is generally felt throughout the injured side. Initially, only do this and repeat. Once this exercise has been mastered and no extreme pain is felt, begin stretching your fingers back. Repeat with different variations, tilting your hand up, backwards, or downwards.

Complications:

• Neurologic - Chronic pain

• Arterial

• Thrombosis, Thromboembolism, Acute ischemia

• Venous - Thrombosis