What is thoracic outlet syndrome?

Thoracic Outlet Syndrome (TOS)

Thoracic outlet syndrome (TOS) is a condition caused by compression of neurovascular structures (brachial plexus, subclavian artery, and/or subclavian vein) at the superior thoracic outlet, resulting in three distinct variants: neurogenic TOS (95% of cases), venous TOS (4-5%), and arterial TOS (1%), each with characteristic symptoms based on the compressed structure. 1, 2

Types and Clinical Presentation

Neurogenic TOS (nTOS)

• Most common form (95% of cases)
• Symptoms: Upper extremity pain, numbness, tingling, weakness
• Caused by compression of the brachial plexus (primarily lower trunk)

Venous TOS (vTOS)

• Accounts for 4-5% of cases
• Symptoms: Arm swelling, heaviness, discoloration
• Often presents with subclavian vein thrombosis (Paget-Schroetter disease)

Arterial TOS (aTOS)

• Least common (1% of cases)
• Symptoms: Claudication, coldness, pallor, decreased pulses
• May present with arterial thrombosis or embolization

Etiology and Pathophysiology

TOS develops due to:

• Congenital abnormalities (cervical ribs, fibrous bands)
• Anatomical variations (scalene muscle insertions, pectoralis minor variations)
• Trauma (neck injuries)
• Repetitive stress (occupational or sports-related)
• Postural abnormalities

The compression occurs in one of three anatomical spaces:

1. Interscalene triangle
2. Costoclavicular space
3. Retropectoralis minor space

Diagnosis

Physical Examination

• Provocative maneuvers to assess for diminished radial pulse:
  • Adson's Test
  • Wright's Test
  • Eden's Test
• Note: Multiple tests should be performed as individual tests lack sensitivity/specificity 1
• Systolic blood pressure difference >25 mmHg between arms is significant 1

Imaging

• MRI of the brachial plexus is the recommended imaging modality for diagnosing TOS 1

• Protocol should include:

  • High-resolution T1-weighted and T2-weighted sequences
  • Sagittal and axial planes
  • Evaluation in both neutral and arms-abducted positions to demonstrate dynamic compression
  • Orthogonal views through oblique planes of the plexus 1

• For vascular TOS:

  • CT venography
  • MRI/MRV
  • Duplex ultrasound 1

• Important caveat: Avoid relying solely on axial imaging slices as this can misrepresent stenosis severity 1

Management

Conservative Treatment (First-Line)

• Targeted physical therapy:
  • Latissimus dorsi stretching and release
  • Postural correction
  • Strengthening of antagonist muscles
  • Activity modification 1
• Anti-inflammatory medications
• Weight loss if applicable 2
• Botulinum toxin injections in selected cases 2

Surgical Management

Indicated when conservative treatment fails:

For Neurogenic TOS:

• Brachial plexus decompression
• Neurolysis
• Scalenotomy with or without first rib resection 2

For Venous TOS:

• Multimodal approach:
  • Catheter-directed thrombolysis for acute thrombosis
  • Immediate anticoagulation
  • Surgical decompression (typically planned within 4-6 weeks after thrombolysis)
  • Possible endovascular intervention 1
• Important: Avoid stent placement before surgical decompression 1

For Arterial TOS:

• Revascularization for symptomatic patients with:
  • TIA/stroke
  • Coronary subclavian steal syndrome
  • Severe ischemia 1

Surgical Approaches:

• Transaxillary approach: Preferred for first rib excision 3
• Supraclavicular approach: Favored for scalenotomies 3
• Combined approach: When larger field of view is required 3

Post-Surgical Rehabilitation

• Critical for long-term success
• Immediate post-surgery: Passive and assisted mobilization of shoulder
• 8 weeks post-surgery: Begin resistance strength training 1

Complications and Pitfalls

• Delayed diagnosis beyond 14 days can significantly worsen outcomes 1
• Surgical complications include:
  • Injury to subclavian vessels (potentially leading to exsanguination)
  • Brachial plexus injury
  • Hemothorax
  • Pneumothorax 2
• Inadequate surgical decompression may lead to persistent symptoms 1
• Premature stent placement before addressing underlying compression can lead to stent fracture or thrombosis 1

Epidemiology

• Prevalence: 1-10 per 100,000 people 1, 2
• More common in women than men 4
• Often affects young adults (average age 26.4 years in one study) 4

TOS requires a coordinated team approach involving thoracic surgeons, neurologists, and physical therapists for optimal management 4. With proper patient selection and appropriate treatment, satisfactory outcomes can be achieved in the majority of cases.