Thoracic outlet syndrome

Last revised by Craig Hacking on 9 May 2024

Thoracic outlet syndrome refers to a group of clinical syndromes caused by congenital or acquired compression of the brachial plexus or subclavian vessels as they pass through the superior thoracic aperture 11

Clinical presentation will depend on the structure compressed and the degree of compression:

Combined neurovascular symptoms and signs may be present. The findings are exacerbated by certain arm positions and maneuvers, particularly with the arms raised (abducted) above the head 9.

There are three common sites of compression:

The scalene triangle is defined by the first rib and the anterior and middle scalene muscles and is the most medial compartment. The subclavian artery and branches of the brachial plexus pass through the borders of this triangle while the subclavian vein passes anterior to it.

  • scalenus anticus syndrome: abnormal insertion of scalenus anterior onto 1st rib (commonest cause)

  • congenital cervical rib

  • bony abnormality of 1st rib or clavicle (congenital anomaly, malunited fracture, callus, Paget disease, tumor)

  • elongated C7 transverse process

  • muscle hypertrophy

  • fibrous bands

  • supraclavicular tumor or lymphadenopathy

Chest radiography is typically performed to exclude an underlying bone abnormality.

Imaging with ultrasound, contrast-enhanced CT, MRI or conventional angiography is useful for detecting vascular thoracic outlet syndrome (e.g. arterial and/or venous compression). Imaging is performed with the patient’s arms both in the raised (abducted) and neutral (adducted) positions for comparison.

MR imaging is useful in patients with neurogenic thoracic outlet syndrome particularly in evaluating the brachial plexus and surrounding structures.  

Imaging findings of thoracic outlet syndrome include 10:

  • neurogenic thoracic outlet syndrome 

    • bone and soft-tissue abnormalities 

    • loss of fat about brachial plexus with abduction

    • edema in brachial plexus

  • venous thoracic outlet syndrome

    • bone and soft-tissue abnormalities

    • axillosubclavian vein thrombosis

    • enlarged collaterals

    • fixed axillosubclavian vein stenosis at the site of dynamic narrowing

    • axillosubclavian vein narrowing with abduction

  • arterial thoracic outlet syndrome

    • bone and soft-tissue abnormalities

    • axillosubclavian artery aneurysm or pseudoaneurysm

    • arterial thrombus

    • distal emboli

    • enlarged collaterals

    • fixed axillosubclavian artery stenosis at site of dynamic narrowing

    • axillosubclavian artery narrowing with abduction

Treatment of arterial thoracic outlet syndrome is surgical intervention. Treatment is required to treat or prevent acute thromboembolic events.

Stent placement is not recommended as an initial treatment, since stent placement alone without surgical intervention generally fails 16. The presence of a stent can limit options for vein reconstruction after stent failure.

Treatment of venous thoracic outlet syndrome depends primarily on the presence and extent of associated venous thrombosis and may include anticoagulation, thrombolysis, or surgical decompression.

Long-term post-surgical complications
  • brachial plexus and phrenic nerve dysfunction due to the proximity of structures during thoracic outlet decompression surgery 12,13

    • if a hemidiaphragm is elevated outside the initial postoperative period, phrenic nerve palsy should be considered

  • apical lung herniation due to violation of the apical pleura, allowing lung to herniate into the supraclavicular space 14

    • may require a wedge resection to treat the hernia.

  • graft occlusion in cases of thoracic outlet decompression with artery bypass 15

The term "thoracic outlet syndrome" is thought to have been coined by R M Peet et al. in 1956 8.

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