Pathogenesis

Obstruction / compression of the structures in the thoracic inlet

1. Congenital
   • Cervical rib (C7) - compresses subclavian artery between rib and scalenus or clavicle
2. Acquired
   • Fractured clavicle
   • Hypertrophy of scalene muscles
   • Pathological enlargement of 1st rib

Approach

• Expose arms and shoulder
• Expose contralateral arm

1. Inspection

   

   • Look at arm
   • Venous outflow from arm - oedema, cyanosis, pallor (reduced return)
   • Arterial flow to arm: patchy gangrene of tips of fingers and palm, fingertip necrosis
   • Neurological supply to arm: wasting of muscles of han d (T1 / ulnar nerve)
2. Palpation
   • Neck: cervical rib may be palpable in supraclavicular fossa
   • Pulsatile mass may be present (due to post-stenotic dilation)
   • Evidence of oedema
   • Radial pulse usually present and normal
   • Test sensation in dermatomes of arm
3. Percuss
4. Auscultation
   • May have bruit over subclavian artery

Differential diagnosis

1. Arterial symptoms
   • Raynauld's
   • Thromboangitis obliterans
   • Takayasu's aortitis
2. Venous symptoms
   • Axillary vein thrombosis
   • Damage to axillary drainage from surgery (breast)
3. Neurological symptoms
   • Cervical spondylosis
   • Pancoast's tumour
   • Cervical disc protrusions
   • Ulnar nerve neuropathy

Investigations

1. CXR/outlet views: Cervical rib or prominent transverse process
2. Doppler examination: quantify postural changes and post-stenotic dilation
3. Arteriograms: of subclavian artery - marked kink in artery or even vein, sometimes localised aneurysm at the site of the narrowing