A Martin-Gruber anastomosis (MGA) is a connection from the

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has contr ...

to the

ulnar nerve In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...

in the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...

. An anastomosis occurs when two structures that normally are not connected have a connection. In this case the connection is a nerve. The Martin-Gruber anastomosis is most common anastomosis that occurs between these two nerves. This connection carries motor axons which innervate some of the usually ulnar nerve innervated intrinsic muscles. This inconstant pattern of connection can serve as explanation for a difficult or challenging

differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...

. In one study, the MGA was found in 22.9% of

cadaver A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...

specimens, while another found the incidence at ~11%. This relatively high incidence demonstrates the necessity for healthcare specialists to factor the MGA into their diagnoses.

Types

There are six types of Martin-Gruber anastomoses.

Clinical Significance

In the setting of proximal ulnar nerve injury, a Martin-Gruber anastomosis can prevent the complete paralysis of the intrinsic muscles of the hand.

References

*{{cite book , title=Gray's Anatomy 40th ed. , last=Standring , first=Susan , year=2008 , publisher=Elsevier , isbn=978-0443066849 , page=854 Nerves of the upper limb Anatomical variations