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During a busy ED shift, your 40yo charge nurse asked you to look at his hand. He is known avid mountain biker. He has pain in his right 4th and 5th digits. . He feels a lack of coordination and a feeling of “clumsiness” of the hand. Where is his possible nerve compression and what do you expect to find on exam?
Ulnar nerve entrapment is sometimes called “handlebar palsy.”
Compression location is Guyon’s canal.
The ulnar nerve supplies the intrinsic muscles of the hand AND the extrinsic muscles for flexion of the 4th and 5th digits. This is what aids in a “power grip” and why he may have diminished grip strength on exam.
Also innervates the ADDuctor pollicis and 1st dorsal interosseous muscles (pinch)
Note the ulnar nerve also passes through the radial tunnel at the elbow. Entrapment here is called Radial tunnel syndrome or Cubital tunnel syndrome and causes forearm pain and paresthesias in the 4th and 5th digits with grossly normal motor and sensory function.