Martin-Gruber anastomosis

Last revised by Rohit Sharma on 16 Aug 2023

Martin-Gruber anastomosis is a common type of, and is the most clinically relevant, interneural communication between the median nerve and ulnar nerve in the forearm.

Most commonly, motor fibers from the median nerve cross to join the ulnar nerve, although at least four patterns (or types) have been described 1,2.

Marin-Gruber anastomosis is a common anatomical variant, with a reported prevalence between 5-50% 2, although this varies significantly between studies of different methodologies. There may be an autosomal dominant pattern of inheritance observed 2.

This anastomosis was first described by Martin in 1763 before being highlighted again by Gruber in 1870 2.

Although not usually of significance to the physical examination, presence of a Martin-Gruber anastomosis can confound upper limb nerve conduction study interpretations, such as in patients with or being investigated for carpal tunnel syndrome 3.

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