What does a nerve conduction finding of Martin-Gruber anastomosis indicate in the evaluation of ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

The anatomic variant known as Martin-Gruber anastomosis is seen during routine nerve conduction studies and can pose a diagnostic dilemma if not identified as such. It is an anomalous pattern of innervation occurring between the median and ulnar nerves in the forearm. [137]

In a Martin-Gruber anastomosis, a crossover of axons from the anterior interosseous nerve (the exclusively motor branch of the median nerve) to the ulnar nerve in the forearm usually occurs. In such cases, no sensory fibers are involved in the crossover. However, in a small minority of cases, the crossover can occur from the main median trunk (in which case some sensory nerve fibers may cross over as well).

The Martin-Gruber anomaly occurs in 10-30% of individuals, and 60-70% of those affected show the anomaly bilaterally. In some families, an autosomal dominant inheritance is possible, though a gene controlling this occurrence has not been identified.


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