Thoracic outlet syndrome

Thoracic outlet syndrome (TOS) is an umbrella term for conditions involving the compression of neurovascular structures (e.g., the brachial plexus or the subclavian artery or vein) as they pass from the lower neck to the armpit. Causes include trauma, tumors, or the presence of a cervical rib. Neurogenic TOS is the most common type and involves the compression of the brachial plexus, leading to neck pain and numbness and tingling in the fingers. Arterial TOS involves compression of the subclavian artery and presents with pain, pallor, coldness, and pulselessness in the affected arm, especially during overhead activities. Venous TOS results in pain, cyanosis, and swelling of the arm. Imaging techniques such as duplex sonography, X-ray, MRI, or electrodiagnostic testing are used to detect the cause of TOS. Mild symptoms should be treated with pain medication and physical therapy. Surgical resection of the causal structures might become necessary in the case of progressive neurologic dysfunction or acute vascular insufficiency.

• Compression of subclavian vessels and the lower trunk of the brachial plexus (mainly occurs within the scalene triangle) due to:
  • Physical trauma (e.g. hyperextension neck injuries)
  • Repetitive motion of the abducted and externally rotated shoulder; (e.g., tennis, baseball, swimming, repetitive throwing, carrying heavy objects overhead)
  • Structural abnormalities
    • Bones: anomalous cervical rib , collarbone fracture, exostoses of the first rib or collarbone ^[1]
    • Soft tissue: hypertrophic muscles in athletes and weight lifters, poor posture and obesity, hematoma, tumors (e.g., Pancoast tumor)

Clinical features of TOS depend on the anatomic structure affected by compression and are more pronounced during and after overhead activity.

• Compression of parts of the brachial plexus (95% of cases) ^[2]
  • Sensory loss or paresthesia (follows the distribution of the ulnar nerve)
  • Pain in the neck and arm
  • Gilliatt-Sumner hand: atrophy of intrinsic hand muscles, including the thenar, hypothenar, lumbrical, and interossei muscles
• Compression of the subclavian vein (up to 3% of cases) ^[2]
  • Swelling
  • Venous distention
  • Diffuse hand or arm pain
  • Heaviness
  • Risk of thrombosis of the arm (Paget-Schroetter disease)
• Compression of the subclavian artery (< 1% of cases) ^[2]
  • Mild arm ache and fatigue
  • Pulselessness, pain, pallor, paresthesia, and poikilothermia (5 Ps)
  • ↓ Blood pressure of > 20 mm Hg in the affected arm compared to the contralateral arm
  • Ischemia can lead to ulcerations and gangrene of the affected arm.

Swelling and venous distention in the arm may be a sign of venous thrombosis of the arm.

• Provocation tests
  • Adson test: a provocation test that is used to reproduce symptoms of TOS
    • Maneuver
      • The patient sits in a relaxed position while the examiner palpates the radial pulse.
      • Passive abduction of 90° and lateral rotation and extension of the arm
    • Interpretation
      • Positive: reduced or absent pulse or paresthesia
      • Negative: no change in pulse or sensation
  • Wright test: a provocation test used to reproduce paresthesia and changes in the radial pulse by performing the following maneuvers
    • Maneuver
      • Passive abduction of the shoulder to 90° followed by external rotation and flexion of the elbow
      • Hyperabduction of the arms over the head
    • Interpretation
      • Positive: reduced/absent pulse or paresthesia
      • Negative: no change in pulse or sensation
  • Roos stress test: a provocation test used to reproduce symptoms of TOS
    • Maneuver: Both shoulders are positioned in abduction and are externally rotated at 90° angles, with elbows flexed at 90°, while the patient repeatedly makes a fist and then relaxes the hand.
    • Interpretation
      • Positive: sensation of heaviness or fatigue in affected limb
      • Negative: no change in sensation
• Imaging
  • Radiographs of the spine, shoulder, collarbone might show bony abnormalities
  • CT or MRI imaging mainly to exclude other conditions that manifest similarly (e.g., rotator cuff tear, Pancoast syndrome, cervical disc disorders, fibromyalgia)
• Other: depend on suspected underlying pathology
  • Neurogenic TOS: electromyography/nerve conduction studies
  • Venous TOS: duplex ultrasonography
  • Arterial TOS: MR angiography

• In mild cases
  • Physical therapy
  • Weight reduction
  • NSAIDs
  • Thrombolytics with continued anticoagulation in the case of venous thrombosis
• Thoracic outlet decompression surgery: in cases of acute vascular insufficiency or progressive neurologic dysfunction or if conservative treatment fails
  • Transaxillary resection of the cervical rib or first rib
  • Anterior scalenectomy: a surgical procedure in which the anterior scalene muscle is resected
  • Angioplasty or venous/arterial bypass for severely narrowed vessels