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Orthopaedics · Hand: Guyon canal syndrome
Sample itemA long-distance cyclist has numbness of the little finger and weakness of finger abduction with sensation over the dorsum of the hand preserved. Where is the ulnar nerve compressed?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
D. Guyon canal at the wrist
Compression in Guyon canal by handlebar pressure causes motor and sensory loss in the palmar ulnar distribution, sparing the dorsal ulnar sensory branch, which leaves the nerve about 5 cm proximal to the wrist. Cubital tunnel compression affects the dorsal sensation too.
Option by option
A. Cubital tunnel at the elbow
Elbow lesions affect the dorsal ulnar cutaneous branch.
B. Arcade of Struthers
The arcade of Struthers is a proximal arm site, and would affect dorsal sensation.
C. Carpal tunnel
The carpal tunnel contains the median nerve.
D. Guyon canal at the wrist (correct)
Correct. Sparing of the dorsal ulnar sensation localises the lesion to Guyon canal.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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