Communications between the Median and Ulnar nerves


The Median and Ulnar nerves don’t give any branches in the arm. In the forearm and the hand, four communications have been described between them: two in the forearm and two in the hand.

Communications in the Forearm

Communicating branch may rise from:

  1. Median (or anterior interosseous nerve) to Ulnar nerve- Martin-Gruber anastomosis

[ ๐Ÿ’ก Aid to memory: Mโ†’U – Its all in the name!]

Martin-Gruber anastomosis
Martin-Gruber anastomosis [CB– Connecting Branch]
It has an autosomal dominant inheritance pattern. It is more common on the right side and has no sex predilection.

2. Ulnar to Median nerve- Marinacci communication or reversed Martin-Gruber anastomosis.

Marinacci communications
Marinacci communication

It’s rare compared to Martin- Gruber anastomosis.

Communications in the Hand

Communicating branch may rise from:

  1. Median (recurrent branch) to Ulnar (deep branch) nerve- Riche- Cannieu anastomosis, or thenar ansa.
Riche-Cannieu anastomosis
Riche-Cannieu anastomosis

It has an autosomal dominant inheritance pattern. Its incidences is 70- 80% (less frequently present in African Americans)

2. Ulnar to Median nerve (between the common digital nerves arising from them)- Berretini anastomosis, ramus communicans or superficial communicating branch.


Berretini anastomosis
Berretini anastomosis


Since many investigators found its incidence to be over 80%, the Berretini anastomosis should be considered a normal structure rather than an anatomic variation. It has no age, sex or race predilections.



  1. Article: Nadire Unver Dogan et al. The communication between the ulnar and median nerves in upper limb. Neuroanatomy 2009-8: 15โ€“19
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