Comprehensive Summary of Anastomoses between the Median and Ulnar Nerves in the Forearm and Hand

Abstract

Four main presentations of median-ulnar anastomosis exist. Those manifesting in the forearm include Martin–Gruber and Marinacci, while those found in the hand are referred to as Riche–Cannieu and Berrettini. Martin–Gruber anastomosis involves branching of the median nerve proximally to ulnar nerve distally. Marinacci anastomosis, the rarest of all the presentations, is often termed reverse Martin–Gruber, with the ulnar nerve stemming proximally to meet the median nerve distally in the forearm. Riche–Cannieu anastomosis occurs as an interconnection between the recurrent branch of the median nerve and the deep branch of the ulnar nerve in the hand. Berrettini anastomosis is the most frequently encountered of the anomalies and is described as a neural connection between common digital nerves of the ulnar and median nerves. Due to altered innervation patterns, musculoskeletal disorders of the forearm and hand may present with misleading symptoms. Additionally, existence of an anastomosis may require an alteration of surgical methods or be a source of iatrogenic injury. Consequently, knowledge of these anastomoses is crucial to clinical practice. Therefore, the objective of this review is to concisely present the most relevant information regarding median and ulnar anastomoses in the forearm and hand.

Neurophysiological and clinical aspects of nerve communications of the upper and lower extremities

“…In types I and II, nerve fascicles head from the median to the ulnar nerve, while in type III (Cannieu and Riché anastomosis) they head from the ulnar to the median [22][23][24] (Figure 1). Furthermore, we can also talk about the four major types of anomalous interconnections between the median and ulnar nerves in the forearm and hand: Martin-Gruber anastomosis (MGA), Marinacci anastomosis (MA), Riche-Cannieu anastomosis (RCA), and Berrettini anastomosis (BA), with the former two occurring in the forearm and the latter two arising in the hand 25 . MGA is considered to follow an autosomal dominant pattern of inheritance 17,[26][27] and has been linked to Trisomy 21 with bilateral presentation 28 .…”

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“…These anastomoses may alter the clinical and electrophysiological manifestations of different neuromuscular diseases of the forearm and hand, may modify the required surgical procedures, and may be a source of iatrogenic nerve injury. [31][32][33][34] Diseases of Riche-Cannieu anastomosis in the palm may be misdiagnosed as severe carpal tunnel syndrome of the median nerve with consequent unneeded performance of a surgery. 35 Anastomoses were also determined between the musculocutaneous nerve and other major nerves in the arm and forearm.…”

Electrodiagnostic description of a rare variant of Berrettini anastomois: A case report

“…BA is reported to have a high prevalence of 60.9%, due to which, it is generally considered to be a normal anatomical structure rather than a variation. In the vast majority (86.2% of all BA) the communicating branch (CB) arises from 4th common digital nerve (CDN), branch of UN in palm and joins the 3rd CDN, a branch of MN ( Illustration 2 ) [ [1] , [2] , [3] ]. BA is named after Pietro Berrettini da Cortona, an Italian painter who provided the earliest illustration of this communication in 1741 [ 4 ].…”