What are distal entrapment sites in ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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After the ulnar nerve passes distal to the elbow, [42, 43, 20] it makes several important divisions. The first branches to come off are those that go to the flexor carpi ulnaris. Further distally, the branches to the flexor digitorum profundus muscles of digits 4 and 5 arise.

Although the nerve could be injured or entrapped at any point along its course, four sites have been identified as the most common locations of entrapment in relation to the canal of Guyon (see the image below).

Diagram shows ulnar nerve distal to elbow region. Diagram shows ulnar nerve distal to elbow region. Dorsal ulnar cutaneous nerve (lavender) branches off main trunk (blue). Although course is not followed in detail after that, lavender region on sensory dermatome diagram shows where this sensory nerve innervates skin. Similarly, palmar cutaneous sensory nerve (yellow) branches off to innervate skin area depicted in yellow. Superficial terminal branch is mostly sensory (see green-colored skin on palmar surface), though it also gives off branch to palmaris brevis. Deep terminal branch has no corresponding skin area, because it is solely motor-innervating muscles shown, as well as others not explicitly depicted. Nerve could be pinched or injured anywhere, but sites labeled I-IV are more commonly involved.

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