carpal tunnel syndrome

see also:

• paraesthesiae or numbness
• Wesley Hand Centre's patient information sheet (pdf)
• Victorian Better Health Channel - carpal tunnel syndrome
• The Women's - Mx guidelines for pregnant women
• WorkCover SA
• NINDS Carpal Tunnel Syndrome Fact Sheet

• 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

• 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:
  • arthritis at the wrist eg. rheumatoid arthritis
  • diabetes
  • hypothyroidism
  • past wrist trauma
  • congenital factors - some have smaller carpal tunnels than others

• 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

• 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

• 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

• 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

• 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

• 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

• 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
• non-steroidal anti-inflammatory drugs (NSAIDs) if pain is problematic
• 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:
  • consider diuretics and corticosteroid injection
  • 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