Carpal Tunnel Syndrome

Peripheral neuropathy caused by acute or chronic compression of the median nerve by the transverse carpal ligament

Aetiology

  • Mostly idiopathic
  • Can occur secondary to many conditions
    • RA - synovitis means less space
    • Acromegaly
    • Conditions resulting in fluid retention e.g. pregnancy, diabetes, chronic renal failure, hypothyroidism
      • In pregnancy the symptoms usually subside after birth
  • Can be a consequence of fractures around the wrist
  • Women affected up to 8x more than men

Pathophysiology

  • The carpal tunnel of the wrist is formed by the carpal bones and the flexor retinaculum
  • The median nerve passes through the carpal tunnel along with 9 flexor tendons (4 x FDS, 4 x FDP, 1 x FPL) with their synovial covering
    • Medial nerve supplies motor innervation to LOAF muscles, and sensory innervation to palmar aspect of hand, thumb, index, middle and radial half of ring finger
  • Any swelling within the confines of the carpal tunnel may result in median nerve compression
  • Whilst the flexor tendons are not particularly susceptible to pressure, nerves are highly sensitive
notion image

Clinical presentation

Symptoms

  • Parathesiae in the median nerve innervated digits (thumb and radial 3½ fingers) which is usually worse at night
  • Loss of sensation and sometimes weakness of the thumb
  • Relieved by shaking the hand
  • Palmar sensation often spared
  • Clumsiness in the areas of the hand supplied by the median nerve

Signs

  • Demonstrable loss of sensation and/or muscle wasting of the thenar eminence (with chronic severe cases) - examine LOAF muscles especially APB
  • Symptoms can be reproduced by performing Tinel’s test (percussing over the median nerve) or Phalen’s test (holding the wrists hyper‐flexed, which decreases space in the carpal tunnel)

Investigations

  • Questionnaire to stratify for nerve conduction study
  • Nerve conduction studies - slowing of conduction across the wrist

Management

Conservative

  • Wrist splints at night to prevent flexion
  • Corticosteriod injections

Surgical

  • Carpal tunnel decompression involves division of the transverse carpal ligament under local anaesthetic
  • Usually a highly successful operation, although there is risk of damage to the median nerve or one of its smaller branches