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

Clinical features

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