What are the possible patterns of Martin-Gruber anastomosis 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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The fibers involved are from the C8/T1 nerve roots. Three patterns of Martin-Gruber anastomosis are commonly recognized, as follows (see the image below):

  • Type I (second most common pattern) - The hypothenar muscles are involved

  • Type II (most common pattern) - The crossover fibers innervate the first dorsal interosseous muscle

  • Type III (least common pattern) - The thenar muscles, typically the adductor pollicis and the flexor pollicis brevis rather than the abductor pollicis brevis, are involved; sometimes other muscles, including forearm muscles such as the flexor digitorum superficialis and the flexor digitorum profundus, are involved as well

    Normal median and ulnar patterns are compared with Normal median and ulnar patterns are compared with those of 3 commonly recognized types of Martin-Gruber anomaly.

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