Thoracic outlet obstruction
Pathogenesis
Obstruction / compression of the structures in the thoracic inlet
- Congenital
- Cervical rib (C7) - compresses subclavian artery between rib and scalenus or clavicle
- Acquired
- Fractured clavicle
- Hypertrophy of scalene muscles
- Pathological enlargement of 1st rib
Approach
- Expose arms and shoulder
- Expose contralateral arm
- 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)
- 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
- Percuss
- Auscultation
- May have bruit over subclavian artery
Differential diagnosis
- Arterial symptoms
- Raynauld's
- Thromboangitis obliterans
- Takayasu's aortitis
- Venous symptoms
- Axillary vein thrombosis
- Damage to axillary drainage from surgery (breast)
- Neurological symptoms
- Cervical spondylosis
- Pancoast's tumour
- Cervical disc protrusions
- Ulnar nerve neuropathy
Investigations
- CXR/outlet views: Cervical rib or prominent transverse process
- Doppler examination: quantify postural changes and post-stenotic dilation
- Arteriograms: of subclavian artery - marked kink in artery or even vein, sometimes localised aneurysm at the site of the narrowing
