Thoracic outlet syndrome

• compression of the neurovascular structures as they exit through the thoracic outlet (cervicothoracobrachial region)
• affects approximately 8% of the population 
• 3-4 times as frequent In woman as in men between the age of 20 and 50 years.
  • Females have less-developed muscles, a greater tendency for drooping shoulders owing to additional breast tissue, a narrowed thoracic outlet and an anatomical lower sternum, these factors change the angle between the scalene muscles and consequently cause a higher prevalence in women
• Congenital Factors:
  • Cervical rib
  • Anomalous muscles
  • Congenital uni- or bilateral elevated scapula
• Acquired Conditions:
  • Postural factors
  • Wrong work posture (standing or sitting without paying attention to the physiological curvature of the spine)
  • Heavy mammaries
  • Trauma –  Clavicle fracture, Rib fracture, Hyperextension neck injury, whiplash
  • Repetitive stress injuries (repetitive injury most often form sitting at a keyboard for long hours)
• Presentation associated with a structural abnormality:
  • gradual onset of sensory +/- motor +/- vascular features
  • sensory – most common; usually pain, referred to the ulnar border of the hand and distal half of the forearm; may be associated with numbness, tingling or paraesthesia; often aggravated by exercise especially with the arm raised; may involve the ring finger
  • motor – weakness and wasting, corresponding to the part of the plexus affected; frequently of thenar muscles, occasionally of interossei
  • vascular – unilateral Raynaud’s phenomenon; radial pulse weaker on affected side with positive Adson’s sign; brittle trophic nails; limb pallor on elevation; susceptible to subclavian venous thrombosis
  • cervical rib may be visible or palpable as a bony swelling in the neck – pressure on this exacerbates sensory features
• Presentation not associated with a structural abnormality:
  • usually less severe than with structural abnormality
  • often, mostly sensory and subjective
  • may be entirely nocturnal developing after lying down for a long period; or may develop during the day after carrying a heavy object
  • more common in women
  • often due to a low shoulder girdle
• Differentials
  • Carpal tunnel syndrome
  • De Quervain’s tenosynovitis
  • Lateral epicondylitis
  • Medial epicondylitis
  • Complex regional pain syndrome
  • Horner’s Syndrome
  • Raynaud’s disease
  • Systemic disorders: inflammatory disease, oesophageal or cardiac disease
  • Upper extremity deep venous thrombosis (UEDVT), Paget-Schroetter syndrome
  • Rotator cuff pathology
  • Glenohumeral joint instability
  • Chest pain, angina
  • Vasculitis

Systematic causes of brachial plexus pain include:

• Pancoast’s Syndrome
• Radiation induced brachial plexopathy

• Tests:
  • Elevated Arm Stress/ Roos test:
    • the patient has arms at 90° abduction and the therapist puts downwards pressure on the scapula as the patient opens and closes the fingers. 
    • If the TOS symptoms are reproduced within 90 seconds, the test is positive
• Investigations
  • blood pressure:
    • lower on the affected side
    • variable with arm abduction
  • X-ray:
    • a bony cervical rib may be seen directly
    • a fibrous band is indicated by an enlarged anterior tubercle of the seventh cervical vertebra
    • apical lung tumour in Pancoast’s syndrome
  • nerve conduction / electromyography:
    • distinguishes thoracic outlet syndrome from other peripheral nerve lesions
  • arteriography:
    • long standing compression of the subclavian artery may result in a post-stenotic dilatation
    • abduction and external rotation of the shoulder may cause complete obstruction of subclavian blood flow in cases associated with a cervical rib
• Treatment
  • The neurological symptoms of thoracic outlet syndrome may be treated conservatively by physiotherapy to improve the muscles which elevate and support the upper limb girdle.
  • Structural abnormalities should be treated surgically if the vascular or neurological problems are severe. The precise operation will depend upon the abnormality present e.g. division of pectoralis minor tendon, resection of clavicle.
  • A symptomatic cervical rib may be treated by scalenectomy and / or removal of the accessory rib.
  • Unusually, a severely damaged section of the artery may have to be replaced by a graft. Afterwards, a chest X-ray should be performed to exclude a pneumothorax.