Fact-sheet: Thoracic outlet syndrome
Updated on 03/06/2026 at 12:20 PM
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Definition
Thoracic outlet syndrome encompasses the full range of clinical manifestations related to intermittent or permanent compression of the brachial plexus, subclavian artery, or subclavian vein. These structures pass through three potential narrowing zones:
- The interscalene triangle (bounded by the anterior and middle scalene muscles, and the 1st rib): passage of the artery and brachial plexus.
- The costoclavicular space: passage of the pedicle and subclavian vein.
- The subpectoral space (beneath the pectoralis minor tendon): a rarer compression zone.
Clinical features
Thoracic outlet syndrome presents three distinct clinical entities that can sometimes coexist:
- Neurologic syndrome (95% of cases): Paresthesias and pain in the C8-T1 distribution (medial border of the arm, forearm, and 4th-5th fingers). Often triggered by cervical trauma (hyperextension). Predominantly affects young women (4:1 ratio).
- Arterial syndrome (< 5%): Exertional ischemia, absent pulses, or severe embolic complications of the hand. Often associated with a cervical rib.
- Venous syndrome: Sudden upper limb edema (axillosubclavian thrombosis or Paget-Schroetter syndrome) or heaviness and intermittent cyanosis with exertion.
Laboratory findings
Laboratory workup can sometimes be useful to exclude differential diagnoses or guide anticoagulant therapy in cases of venous thrombosis.
Radiography
First-line examination to identify predisposing bony factors.
- Rib anomalies: Cervical rib (incidence of 0.002 to 0.5% in the general population), agenesis of the 1st rib or fusion of the 1st and 2nd ribs.
- Clavicular anomalies: Large postfracture callus, non union, or marked postural drooping of the clavicle.
Spinal anomalies: Hypertrophy of the C7 transverse process (variant), vertebral block, or kyphoscoliosis.
Ultrasound
Routine second-line examination for morphological and hemodynamic assessment.
- Protocol: Study in neutral position followed by dynamic maneuver (active abduction at 90° or 180°).
- Arterial signs: Elevation of the artery over a cervical rib, positional or permanent stenosis, and post-stenotic dilatation.
- Venous signs: Assessment for post-thrombotic sequelae (synechiae) and evaluation of positional venous occlusion with development of collateral circulation.
- Limitations: Difficulty in evaluating the terminal retroclavicular segment of the vein.
CT
CT angiography with 3D reconstructions = reference examination for precise anatomical analysis of osteovascular relationships.
- Technique: Contrast-enhanced acquisition in neutral position and in abduction.
- Volume rendering (VRT): Optimal analysis of bony conflicts by artificial subtraction of the clavicle.
- Multiplanar reconstructions (MPR): Assessment of the vascular lumen (stenosis, mural thrombus) and muscular relationships (scalene muscles).
- Indication: Essential in vascular forms; it has no indication in pure neurological syndrome as it does not identify the nerve roots.
MRI
Indicated in cases of atypical neurological symptoms to rule out spinal cord or radicular pathology (disc herniation, neurinoma).
Vascular intervention
Indications restricted to preoperative workup or management of complications:
- Arteriography: Only in cases of acute ischemic complications to document distal emboli and plan the surgical strategy.
- Phlebography: Useful for evaluating residual stenosis after recanalized thrombosis prior to potential venoplasty.
Management
- Conservative treatment: First-line option for pure neurological syndrome (physiotherapy for 3 to 6 months to correct posture and strengthen the shoulder suspensory muscles).
- Surgery: Indicated upfront in cases of vascular complications or major compressive bony anomaly. It generally consists of resection of the first rib and associated osteoligamentous anomalies (supraclavicular approach preferred).
Differential diagnosis
- Neurological: Distal entrapment syndromes (carpal tunnel, ulnar nerve at the Elbow), cervical disc herniation, cervical osteoarthritis, or brachial plexus tumor.
- Vascular: Raynaud's disease, vasculitis, or venous thrombosis of other etiologies (hypercoagulable states).
