I. Anatomy, pathophysiology, and epidemiology
  1. No definitive diagnostic criteria but describes compression of structures in the triangle formed by the first rib, anterior scalene m., and middle scalene m.
  2. Symptoms can reflect compression of the artery (subclavian), nerve (brachial plexus), and/or vein.  Nerve is most common (95% of cases); arterial is least common and is usually accompanied by a cervical or anomalous first rib
  3. Female:Male 3:1

II. Clinical Presentation

  1. For neurologic:
    1. History of antecedent trauma is common
    2. UE numbness/paresthesia (variable location; most commonly in distribution of ulnar n.)
    3. Symptoms may worsen with physical activity (particularly repetitive abduction of shoudler) or cold
    4. "Adson's test" to diagnose (not highly sensitive):
      1. The sign is the disappeaerance of the radial pulse as the patient holds his/her breath and hols his/her neck in hyperextension and rotated toward affected side, and the examiner extends and externally rotates the upper arm
    5. Motor weakness is uncommon
  2. Arterial: Usually result from embolization (pain, paresthesia, pallor, pulselessness, coldness).  Can be diagnosed by magnetic resonance angiography; Usually treated with surgical rib decompression, thrombectomy and/or reconstruction of the affected segment of subclavian artery.
  3. Venous ("Paget-Schroetter syndrome")-Due to thrombotic or nonthrombotic compression of the axillary or subclavian vein. Excessive arm activity can predispose.  Usually presents with cyanosis, arm swelling and pain. If doppler ultrasound shows thrombosis, thrombolysis and surgical decompression of the thoracic outlet is sometimes done and obviates need for long-term anticoagulation.

III. Diagnostic workup (for neurologic)

  1. C-spine films can be done to look for presence of a cervical rib (a congenital condition that can predispose; 1% of people have it)
  2. Nerve conduction studies may show a slowing in ulnar and/or median nerves across the thoracic outlet
  3. MRI can show non-bony causes of compression of the thoracic outlet e.g. fibrous bands
  4. EMG is usually normal

IV. Treatment (for neurologic)

  1. Start with conservative management-rest, scalene stretches, strengthening of shoulder girle
  2. NSAIDs etc. for pain
  3. Resection of the first rib is sometimes performed but no randomized trial data for this as of 2011
  4. Dorsal sympathectomy-Sometimes done if surgery fails

(Sources include Core Content Review of Family Medicine, 2012)