Communications between the Median and Ulnar nerves

(Last Updated On: January 31, 2018)

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 (Martin- GruberMarinacci/ Reversed Martin- Gruber anastomosis) and two in the hand (Riche- Cannieu, Berretini anastomosis). 1

Communications in the Forearm

1. Martin- Gruber anastomosis

Median (or anterior interosseous nerve) to Ulnar nerve. (Note: Mnemonic- It’s all in the name- MU).

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. Marinacci communication / Reversed Martin Gruber anastomosis.

Ulnar to Median nerve.

Marinacci communications
Marinacci communication

It’s rare compared to Martin Gruber anastomosis.

Communications in the Hand


1. Riche- Cannieu anastomosis, or Thenar ansa.

Median (recurrent branch) to Ulnar (deep branch) nerve.

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. Berretini anastomosis

Ulnar to Median nerve (between the common digital nerves arising from them)- aka 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: 15–19



Communications between the Median and Ulnar nerves
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