What causes thoracic outlet syndrome?

Updated: Jan 10, 2019
  • Author: Daryl A Rosenbaum, MD; Chief Editor: Sherwin SW Ho, MD  more...
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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. [18, 19] 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%. [16]

Soft-tissue factors include congenital anomalies such as anomalous fibrous muscular bands near the brachial plexus and hypertrophic muscles in athletes and weight lifters. [19, 20] 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. [21] Thoracic outlet syndrome can be secondary to malunion of a clavicle fracture. [22]

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- [23] or multiple-crush syndrome. [24]

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