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A 48-year-old white female secretary presents with progressive difficulty typing over the past month. She also
notes that her hands begin to feel numb and weak after typing for long periods of time. Upon testing, which of the
following deficits would be predicted?
A. Difficulty in abducting the fifth finger
B. Difficulty in adducting the thumb
C. Difficulty in flexing digits two and three at the metacarpophalangeal joints
D. Loss of sensation over the lateral half of the dorsum of the hand
E. Loss of sensation over the lateral half of the palm
F. Loss of sensation over the medial half of the dorsum of the hand
G. Loss of sensation over the medial half of the palm
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cccccc sensation is not affected because median nerve doesnt pass supperficial to the tunnel.
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The correct answer is C.
This is a classic presentation of a patient with carpal tunnel syndrome, which typically
affects females between the ages of 40 and 60 who chronically perform repetitive tasks that involve movement
of the structures that pass through the carpal tunnel. One important structure that passes through the carpal
tunnel is the median nerve. Patients often note a tingling, a loss of sensation, or diminished sensation in the
digits. There is also often a loss of coordination and strength in the thumb, because the median nerve also
sends fibers to the abductor pollicis brevis, flexor pollicis brevis, and the opponens pollicis. A final function of the
median nerve distal to the carpal tunnel is control of the first and second lumbricals which function to flex digits
two and three at the metacarpophalangeal joints and extend interphalangeal joints of the same digits.
Abduction of the fifth digit (choice A) is a function controlled by the ulnar nerve, which does not pass through the
carpal tunnel.
Adduction of the thumb (choice B) is a function of the adductor pollicis, which is the only short thumb muscle that
is not innervated by the median nerve, but rather by the deep branch of the ulnar nerve.
Sensation of the lateral half of the dorsum of the hand (choice D) is mediated by the radial nerve, which also
does not pass through the carpal tunnel.
Sensation over the lateral aspect of the palm (choice E) is mediated by the median nerve, however the branch
innervating the palm (palmar cutaneous branch of the median nerve) passes superficial to the carpal tunnel.
Sensation over the medial aspect of the dorsum of the hand (choice F) is mediated by the ulnar nerve.
Sensation over the medial aspect of the palm (choice G) is mediated by the ulnar nerve.
