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Carpel tunnel syndrome

Definition
  • Collection of symptoms and signs caused by compression of the median nerve in the carpal tunnel
  • Typical symptoms include numbness and tingling mainly in the first 3 fingers, aching and pain in the anterior wrist and forearm, and clumsiness in the hand
Risk Factors
  • Age >30
  • High BMI
  • Female
  • Damage to wrist
  • RA
  • Diabetes
  • Square wrist
  • Dialysis
    • deposition of amyloid on tendons and other structures within the carpal tunnel
  • Pregnancy
  • Congenital carpal tunnel stenosis
  • Repetitive bending, vibration, twisting of wrist
  • Smoking
Differential diagnosis
  • OA
  • Stroke
  • C6/C7 radiculopathy
  • Ulnar neuropathy
  • Amyotrophic lateral sclerosis
  • Motor neurone disease
  • De Quervain's syndrome
  • Lateral epicondylitis
  • Rotator cuff tendonitis
  • Polyneuropathy
  • Brachial plexopathies
  • Proximal median neuropathy
  • MS
Epidemiology
  • US incidence 3.5 cases per 1000 person-years
  • Prevalence 3.7%
  • Appears to be much more rare in developing countries and in other ethnic groups
  • Rates of CTS have risen considerably over the past several decades, but whether this is due solely to better recognition or a rise in risk factors is debatable
  • CTS is at least 3 times more common in females
Aetiology
  • It is rare to find any single definite cause in a patient
  • Causation is very likely multi-factorial. 
Clinical features
  • Numbness of hand(s)
    • Median nerve distribution
  • Weakness in hand / thenar muscle weakness
    • Median nerve distribution
    • LOAF
      • Lumbricals 1+2
      • Opponens pollicis
      • Abductor pollicis brevis
      • Flexor pollicis brevis
  • Clumsiness
  • Aching and pain in arm
  • Worse at night
  • Intermittent symptoms
  • Gradual onset
Pathophysiology 
  • The final common pathway is the development of raised pressure within the carpal tunnel and/or the median nerve segment that lies within the tunnel
  • The increased pressure could trigger off a chain of negative events that ultimately leads to ischaemia and scarring of the nerve
  • Ischaemia is likely to be the cause of the typical intermittent sensory symptoms of CTS
    • if it remains intermittent, then no axonopathy occurs
  • Pressure on the nerve will also lead to demyelination (and ultimately axonal loss), which is the main finding on neurophysiological testing
    • Demyelination per se causes no symptoms to the patient
    • This may explain in part the subgroup of individuals who have no symptoms of CTS but who have abnormalities on nerve conduction studies
Investigations
  • Electromyogram
    • focal slowing of conduction velocity in the median sensory nerves across the carpal tunnel
    • prolongation of the median distal motor latency
    • possible decreased amplitude of median sensory and/or motor nerves
  • Wrist ultrasound/MRI
    • Hard to distinguish the median nerve
Management

a) conservative
  • Wrist splints, especially at night
b) medical
  • 40-mg methylprednisolone acetate (1 mL volume) +/- local anaesthetic is used
    • The volume should be kept low, as an increase in fluid could exacerbate the already raised pressure in the carpal tunnel
  • Oral steroids do work, but not as well as intracarpal injection
  • Potentially a mild diuretic (e.g., hydrochlorothiazide) if wrist oedema present
  • NSAIDS
c) surgical
  • Surgical release
Prognosis
  • Untreated CTS can spontaneously improve in up to one third of individuals, particularly in younger females 
  • Most studies show about a 70% chance of improvement with splints after a period of weeks to months
  • Most studies show a success rate of between 60% and 70% up to 6 months post-injection with corticosteroids
  • Surgical success rates are about 80% to 90%
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