The anatomic condition of the upper thoracic aperture, with or without additional external factors, predisposes to chronic pressure damage to the brachial plexus and vascular compression. This is particularly true for its caudal portion. Since the exact pathogenetic mechanisms cannot always be proven, the general term thoracic outlet syndrome (TOS) is used.

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Classification of Thoracic Outlet Syndrome

Classification according to clinical presentation:
  • neurogenic TOS
  • vascular TOS
  • mixed TOS (most common)
  • (unclassifiable TOS)
Etiopathogenetic classification
  • scalene syndrome/cervical rib syndrome
  • costoclavicular syndrome
  • hyperabduction (pectoral) syndrome


  • anatomic anomalies
    • cervical rib ( an extra rib that forms above the first rib, growing from the base of the neck just above the collarbone)
    • ligamentous band between the spine and rib
  • poor posture
    • drooping shoulders with anteflexion of the head
  • trauma
    • difficulties may occur with a delay
  • repetitive, monotonous work
    • working at the computer, working on a production line, working with prolonged hand-holding
    • sports (e.g., swimming)
    • repetitive carrying of loads over the shoulder
  • pregnancy
    • TOS may occur during pregnancy due to joints loosening

Clinical presentation

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Diagnostic evaluation

Medical history, clinical examination, provoking tests

Scalene syndrome and cervical rib syndrome
  • the brachial plexus and subclavian artery may be compressed while simultaneously passing through the gap between the anterior and medial scalene muscles
  • this is more likely to occur with abnormal scalene attachment and, especially in the presence of a cervical rib
    • a cervical rib is a rudimentary structure that may occur only as a ligamentous band, which then escapes detection on X-ray examination but is usually visible on MRI or CT scan
    • the cervical rib rarely causes clinical difficulty and usually doesn’t require surgical removal

Adson´s test

  • arm of the standing or seated patient is abducted 30 degrees and held in extension and slight external rotation
  • the patient then extends the neck and turns the head toward the symptomatic shoulder, and is asked to take and hold a deep breath
  • the goal of this test is to tense the anterior and medial scalene muscles
  • the quality of the radial pulse is evaluated in comparison to the pulse in the resting arm
Costoclavicular syndrome
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Hyperabduction syndrome
  • caused by compression of the neurovascular bundle against the coracoid process and pectoralis minor muscle (m. pectoralis minor) during hyperabduction of the arm
  • onset usually during sleep; after awakening, the arm is paralyzed and numb

Wright’s test (hyperabduction test)

  • head forward, while the arm is passively abducted and extended without head tilt
  • the elbow is flexed to no more than 45°; the arm is then held for 1 min (measure radial pulse and monitor for onset of patient symptoms)
  • the test is repeated with the extremity in hyperabduction (end-range of abduction)
  • positive test:  a decrease in the radial pulse and/or reproduction of the patient’s symptoms

Roos test (“elevated arm stress test” or “EAST”)

  • hyperabduction of both upper limbs with elbows held at shoulder height and repeated wrapping and closing of the hand into a fist
  • positive test: 
    • a decrease in the radial pulse and/or reproduction of the patient’s symptoms
    • increasing pain in the neck and shoulder, propagating down the arm
    • paresthesias in the forearm and fingers
    • pallor of the elevated arm, reactive hyperemia when the limb is lowered
Eden´s test (costoclavicular TOS syndrome)
Adsen´s test (scalene syndrome)
Wright´s and Roos test (hyperabduction syndrome)

Other diagnostic methods

  • X-ray of the upper thoracic outlet
    • look for cervical rib
    • exclude other structural pathologies
  • dynamic DSA/CTA or the Doppler ultrasound (during provocation testing)
    • direct demonstration of arterial compression and determination of its severity
    • detection of poststenotic dilatation, detection of intraluminal thrombus within the dilated segment
    • flow pattern change during the provoking maneuver (ultrasound)
      • dampened flow in distal segments + high-resistance flow is found in the proximal subclavian artery

→ more about dynamic CTA here

  • MRI
    • can help locate the site of the plexus or subclavian artery compression
    • it can detect a fibrous band between the spine and the 1st rib or cervical rib
  • EMG
    • detects neuropathic changes
BIlateral cervical rib as a cause of Thoracic Outlet Syndrome
CT angiography in a patient with neurogenic TOS on the right side (green arrow - subclavian artery, red arrow - anterior scalene muscle)
CTA during provoking maneuver (Subiran, 2012)


Conservative treatment

  • physiotherapy to strengthen the corset and shoulder muscles and improve posture → see here
  • relaxation techniques
  • medication (non-steroidal anti-inflammatory drugs – NSAID)

Surgical treatment

  • indications:
    • failure of conservative pain management
    • progressive neurological symptoms (atrophy, sensory deficit, paresis)
    • symptomatic subclavian artery compression with distal hypoperfusion, aneurysm formation, etc.
  • surgery provides pain relief and may halt the progression of neurological disability
  • there is always a risk of periprocedural brachial plexus injury
  • approaches:
    • anterior supraclavicular – resection of the cervical rib and potential fibrous band arising from it
    • transaxillary – partial resection of the first rib

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Thoracic Outlet Syndrome (TOS)