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Excerpt from Thoracic Outlet Syndrome


Synonyms, Key Words, and Related Terms: TOS, vascular thoracic outlet syndrome, vascular TOS, neurologic thoracic outlet syndrome, neurologic TOS, arterial thoracic outlet syndrome, arterial TOS, venous thoracic outlet syndrome, venous TOS, compression of neurovascular structures, pain in the ulnar nerve distribution, paresthesias in the ulnar nerve distribution, cold intolerance, elevated arm stress test, EAST, supraclavicular tenderness, Gilliatt-Sumner hand, edema of the upper extremity, cyanosis of theupper extremity, distended superficial veins of the shoulder, distended superficial veins of the chest, cervical ribs, scalene triangle, congenital fibromuscular bands, elongated transverse process of C7, motor vehicle accident hyperextension injury, effort vein thrombosis, neurovascular entrapment

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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.

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