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carpal_tunnel

carpal tunnel syndrome

introduction

  • this is a common problem mainly affecting adults, particularly line assembly workers, typists or those in 2nd or 3rd trimester pregnancy
  • it is due to compression of the median nerve within the carpal tunnel due to:
    • reduced carpal tunnel space - congenital &/or acquired
    • increased fluid pressure (eg. pregnancy, menopause)
    • increased adipose tissue
    • thickened tendon sheaths
    • thickened median nerve - although this may be a secondary response as well
  • most patients have pain at night (brachialgia paresthetica nocturna) - this may be exacerbated by a flexed wrist posture whilst sleeping
  • the condition needs to be identified and treated early before the nerve damage is irreversible

aetiology

  • overuse
    • typists
    • assembly line workers - have 3x risk compared with typists!
    • knitting
    • wood carving
    • vibrating tools including lawn mowers, long distance driving
  • pregnancy or menopause
  • rapid weight gain
  • prolonged wrist flexion or hyperextension
  • cold exposure
  • other causal aetiologies to be considered:

clinical features

  • pain +/- numbness in the hand and median nerve distribution fingers
  • often referred pain proximally up the arm
  • weakness of thumb muscles and tendency to drop objects
  • potentially if chronic and severe, wasting of the muscles of the hand supplied by the median nerve

Tinel's test

  • gently tapping over volar aspect of wrist with the index finger causes tingling or pain in the hand
  • LR+ = 1.4x
  • NB. this test is also +ve in tenosynovitis of flexor tendons of the hand
  • probably a useless test

Phalen's test

  • full flexion of the wrist causes tingling or pain in the hand
  • LR+ = 1.3x
  • NB. this test is also +ve in tenosynovitis of flexor tendons of the hand
  • probably a useless test

Flick sign / signal

  • The patient is asked, “What do you do when your symptoms are worse?”
  • If the patient responds with a motion that resembles shaking a thermometer, then the sign is +ve
  • LR+ = 21x but only around a 1/3rd will be +ve, but a more useful test than Tinel or Phalen's

Szabo's criteria

  • presence of all 4 of these signs gives a probability of CTS of 86%, whereas if these are all negative then probability is < 1%1):
    • abnormal hand diagram
      • patient asked to shade in the location of symptoms on dorsal and volar hand drawings for both hands
      • diagram then rated as either classic, probable, possible, or unlikely carpal tunnel syndrome
      • sensitivity of diagrams rated classic or probable was 80% and specificity was 90%
    • abnormal sensibility by Semmes-Weinstein testing in wrist-neutral position
      • this is just using a length of monofilament to test light touch before and after a Phalen's wrist position for 5 minutes
    • a positive Durkan's test
      • examiner presses thumbs over carpal tunnel and holds pressure for 30 seconds
      • onset of pain or paresthesia in the median nerve distribution within 30 seconds is a positive result of the test
      • more sensitive than Tinel test
    • night pain
      • 96% of patients with CTS have night pain

DDx

  • median nerve injury at other location
  • Guyon canal syndrome / ulnar tunnel syndrome
  • ulnar nerve injury at the elbow
  • De Quervain's tenosynovitis
  • digital flexor tenosynovitis - can cause pain and a clicking sound when the trigger finger or thumb is bent and straightened
  • thoracic outlet syndrome
    • compression of nerves and blood vessels over the 1st rib
  • reflex sympathetic dystrophy

Mx

  • initially, a splint to avoid wrist flexion - particularly at night
  • avoidance of excessive typing or other causal event
  • avoid heavy lifting
  • elevate hand as much as possible
  • avoid sleeping on the hand
  • avoid prolonged wrist flexion or extension
  • workers can do on-the-job conditioning, perform stretching exercises, take frequent rest breaks, wear splints to keep wrists straight, and use correct posture and wrist position
  • OH&S assessment to optimise ergonomics of keyboard, mouse, etc.
  • rotate tasks among workers
  • consider referral to a hand therapist
  • yoga has been shown to reduce pain and improve grip strength among patients with carpal tunnel syndrome
  • if problematic and not settling, then:
    • referral for nerve conduction studies to confirm the diagnosis
      • however this test does have false positives and false negatives
    • consider wrist US looking for enlarged median nerve
    • consider wrist MRI looking for enlarged median nerve although MRI does not seem helpful
    • once diagnosis is reasonably confirmed then referral to general surgery for possible surgical release of the carpal tunnel by dividing the transverse carpal ligament
carpal_tunnel.txt · Last modified: 2013/07/12 17:47 (external edit)