Did You Know
|Vanessa Simmons, MD
By Dr. Vanessa Sammons MD (Neurosurgeon and Peripheral Nerve Surgeon)
The median and Ulnar nerves have several common anatomical variants:
Bifurcation of the median nerve proximal to the transverse carpal ligament is a relatively common anatomical variation present in 1% to 3.3%.
The Martin-Gruber Anastomosis occurs in the forearm and is described as the proximal extension of the median nerve to the ulnar nerve distally. It is most often efferent. It is commonly unilateral and on the right. The prevalence is 19.5%.
The Marinacci Anastomosis is estimated at 0.7%. It is the reverse of the above, with the ulnar nerve branching proximally to join the median nerve distally in the forearm. It is also mainly efferent.
The Riche-Cannieu Anastomosis is a connection in the hand between the recurrent branch of the median nerve and the deep branch of the ulnar nerve. When the ulnar supplies muscles that are normally median innervated it is abductor pollicis brevis that is most often supplied, followed by the opponens pollicis.
It has a prevalence of 55.5%.
The Berrettini Anastomosis is a connection between common digital nerves of the ulnar and median nerves. The two most affected digital nerves are the fourth joining the third distally. It is usually bilateral. It has a prevalence of 60.9%.
Ref: Smith J, Siddiqui S, Ebraheim N. Comprehensive Summary of Anastomoses between the Median and Ulnar Nerves in the Forearm and Hand. J Hand Microsurg. 2019 Apr; 11(1): 1–5.