Riche-Cannieu anastomosis

Last revised by Rohit Sharma on 3 Dec 2023

Riche-Cannieu anastomosis describes a common interneural communication between the median nerve and the ulnar nerve in the hand.

Generally, this anastomosis is specifically between the deep palmar branch of the ulnar nerve and the recurrent branch of the median nerve, although many variations are described 1. The nature or contents of the anastomosis is highly variable, such that there may be either or both motor (more commonly affected) and sensory fibers involved, and that fibers may go from the median nerve to the ulnar nerve (more common path) or vice versa 2,4.

This is thought to be a common anatomical variant of the upper limb nerves, with a meta-analysis suggesting a pooled frequency of 55% 1. However, individual studies differ significantly in regards to dissection and electrophysiological techniques, with some studies employing very precise techniques finding that Riche-Cannieu anastomoses could be as common as being present to some degree in 80-100% of hands 2. There may be an autosomal dominant pattern of inheritance observed 3.

The anatomical variant was described separately by the French physicians D Riché and A Cannieu in the 1890s 2,5,6.

Clinically, the Riche-Cannieu anastomosis is infrequently of significance, although its presence can confound nerve conduction study interpretations 2,4. However, there are rare instances of 'complete' Riche-Cannieu anastomoses of greater clinical significance, whereby the thenar muscles can be completely innervated by the ulnar nerve, which, for example, can lead to median neuropathy at the wrist having a milder than expected clinical presentation but a severe neuro-electrophysiological phenotype on nerve conduction studies 2,4.

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