Epidemiology
- Occurs in approximately 1 in 500 people
- Most cases are discovered incidentally on x-ray
Etiology
- Congenital overdevelopment of the transverse process of C7
- It is an extra rib that forms above the first rib – grows just above the clavicle
Pathophysiology/Clinical features
- Majority of cases are asymptomatic and do not need treatment
- Some cases lead to thoracic outlet syndrome (see below)
- Compression of the sympathetic chain can cause Horner’s syndrome
Thoracic outlet syndrome (TOS)
- Compression of neurovascular structures as they exit through the thoracic outlet
- Brachial plexus (neurogenic), subclavian artery (arterial), subclavian vein (venous)
- Borders of the thoracic outlet – anterior scalene (anteriorly), middle scalene (posteriorly), first rib (inferiorly)
Clinical features
- Arterial TOS – hand pain, claudication, pallor, cold intolerance, paresthesia
- Venous TOS – cyanosis, feeling of heaviness, arm edema
- Neurogenic TOS – pain, paresthesia, numbness; occipital headaches; loss of fine motor skills; cold intolerance (Raynaud’s phenomenon)
- Symptoms are exacerbated when arm is abducted overhead
Diagnosis
- Adson sign – loss off radial pulse in the arm by rotating head to the ipsilateral side with extended neck following deep inspiration (non specific)
- Doppler arteriography
- MRI – to show soft tissue compression at the thoracic outlet
Treatment
- Stretching, physiotherapy – to relieve compression in thoracic cavity
- Botox – temporarily reduce pain
- Surgery – first rib resection