9.21 Carpal Tunnel Syndrome
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agk's Library of Common Simple Emergencies

Presentation
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The patient complains of pain, tingling, or a 
"pins and needles" sensation in the hand. Onset 
may have been abrupt or gradual but the problem 
is most noticeable upon awakening or after 
extended use of the hand. The sensation may be 
bilateral, may include pain in the wrist or 
forearm and is usually ascribed to the entire 
hand until specific physical examination 
localizes it to the median nerve distribution.

More established cases may include weakness of 
the thumb and atrophy of the thenar eminence. 
Physical examination localizes paresthesia and 
decreased sensation to the median distribution 
(which may vary) and motor weakness, if 
present, to intrinsic muscles with median 
innervation. Innervation varies widely, but the 
muscles most reliably innervated by the median 
nerve are the abductors and opponens of the 
thumb.

What to do:
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- Perform and document a complete examination, 
    sketching the area of decreased sensation 
    and grading (on a scale of 1-5) the 
    strength of the hand.
- Hold the wrist flexed at 90 degrees for 60 
    seconds, to see if this reproduces 
    symptoms. This is known as Phalen's test, 
    and is more sensitive than the reverse 
    (hyperextending the wrist) and more 
    specific than tapping over the volar carpal 
    ligament to elicit paresthesia (Tinel's 
    sign).
- Explain the nerve-compression etiology to the 
    patient, and arrange for additional 
    evaluation and followup. Borderline 
    diagnoses may be established with 
    electromyography (EMG), but cases with 
    pronounced pain or weakness may require 
    early surgical decompression. Anti-inflamm- 
    atory medication, elevation of the affected 
    hand, ice, immobilization with a volar 
    splint, and rest may all help to reduce 
    symptoms.

What not to do:
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- Do not rule out thumb weakness just because 
    the thumb can touch the little finger. 
    Thumb flexors may be innervated by the 
    ulnar nerve. Test abduction and opposition: 
    can the thumb rise from the plane of the 
    palm and can the thumb pad meet the little 
    finger pad?
- Do not diagnose carpal tunnel syndrome solely 
    on the basis of a positive Tinel's sign. 
    Paresthesia can be produced in the distrib- 
    ution of any nerve if one taps hard enough.

Discussion
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There is little space to spare where the median 
nerve and digit flexors pass beneath the volar 
carpal ligament, and a very little swelling may 
produce this specific neuropathy. Trauma, 
arthritis pregnancy, and weight gain are among 
the many factors which can precipitate this 
syndrome. Less commonly, the median nerve can 
be entrapped more proximally, where it enters 
the medial antecubital fossa through the 
pronator teres. Symptoms of this cubital tunnel 
syndrome may be reproduced with elbow extension 
and forearm pronation.

Illustration
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img/cse0921.gif

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 from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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