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For further information, see CMDT Part 20-45: Thoracic Outlet Syndromes

Key Features

Essentials of Diagnosis

  • Compression of neurovascular structures supplying upper extremity

  • Predominant symptoms depend on whether the compression chiefly affects neural or vascular structures

General Considerations

  • Intermittent or continuous pressure on elements of the brachial plexus (> 90% of cases) and the subclavian or axillary vessels by anatomic structures of the shoulder girdle region results in symptoms and signs

  • The neurovascular bundle can be compressed between the anterior or middle scalene muscles and a normal first thoracic rib or a cervical rib

  • Predisposing factors

    • Scarred scalene neck muscle secondary to neck trauma

    • Sagging of the shoulder girdle, resulting from aging, obesity, or pendulous breasts

    • Faulty posture

    • Occupation

    • Thoracic muscle hypertrophy from physical activity (eg, weight-lifting, baseball pitching)

Clinical Findings

Symptoms and Signs

  • Some combination of four symptoms involving the upper extremity: pain, numbness, weakness, and swelling

  • Onset usually gradual but can be sudden

  • Pain radiating from the point of compression to the base of the neck, axilla, shoulder girdle region, arm, forearm, and hand

  • Numbness and paresthesias, distributed to the volar aspect of the fourth and fifth digits

  • Weakness and muscle atrophy

  • Reflexes not usually altered

  • Swelling

  • Some patients spontaneously notice aggravation of symptoms with specific positioning of the arm, at night, or upon prolonged use of the extremities

  • Vascular symptoms consist of arterial ischemia, characterized by

    • Pallor of fingers on elevation of extremity

    • Sensitivity to cold

    • Gangrene of digits (rare)

    • Venous obstruction marked by edema, cyanosis, and engorgement (also rare)

  • Symptoms can be provoked within 60 seconds over 90% of the time by having a patient elevate the arms in a "stick-em-up" position (ie, abducted 90 degrees in external rotation)

  • Obliteration of the radial pulse with certain maneuvers of the arm or neck, once considered a highly sensitive sign of thoracic outlet obstruction, does not occur in most cases

Differential Diagnosis

  • Osteoarthritis of cervical spine

  • Tumors of the superior pulmonary sulcus, cervical spinal cord, or nerve roots

  • Periarthritis of the shoulder


Imaging Studies

  • Chest radiography identifies presence of cervical rib

  • MRI with arms held in different positions useful in identifying sites of impaired blood flow

  • Angiography confirms intra-arterial or venous obstruction

Diagnostic Procedures

  • Conduction velocities of the ulnar and other upper extremity peripheral nerves may help localize the site of compression



  • Required by < 5% of patients

  • More likely to relieve neurologic rather than vascular component that causes symptoms

Therapeutic Procedures

  • Conservative measures (eg, physical therapy) to relieve compression ...

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