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NBME 20 Answers

nbme20/Block 4/Question#24

A 27-year-old man comes to the physician because of ...

Deep branch of the ulnar nerve at the hook of the hamate bone

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 +4  upvote downvote
submitted by celeste(32),

The adductor pollicis muscle is innervated by the ulnar nerve, giving this guy a difficult time holding a sheet of paper.





 +2  upvote downvote
submitted by hello(62),

Guyon Canal Syndrome is due to an Ulnar Nerve lesions and is associated with bicycle handlebar use.

Also FINGER abduction and adduction is mediated by ulnar nerve. The patient is having trouble with FINGER abduction and adduction.

The Froment sign is testing ADDUCTOR POLICIS ACTIVITY, which is mediated by the ULNAR NERVE activity. It is NOT testing thumb opposition, which would be mediated by the median nerve.

See Froment sign





 +1  upvote downvote
submitted by neonem(251),

Most of intrinsic muscles of the hand are innervated by ulnar nerve - chronic compression at the hook of hamate could lead to nerve ischemia





 +1  upvote downvote
submitted by xxabi(90),

Bicycle handlebar injury traditionally damages ulnar nerve @ the hook of the hamate bone