The anterior interosseous nerve (volar interosseous nerve) is a branch of 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 ...

that supplies the deep muscles on the anterior of 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 an ...

, except the ulnar (medial) half of the

flexor digitorum profundus The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Togethe ...

. Its nerve roots come from C8 and T1. It accompanies the

anterior interosseous artery The anterior interosseous artery (volar interosseous artery) is an artery in the forearm. It is a branch of the common interosseous artery. Course It passes down the forearm on the palmar surface of the interosseous membrane. It is accompanied ...

along the anterior of the

interosseous membrane of the forearm The interosseous membrane of the forearm (rarely middle or intermediate radioulnar joint) is a fibrous sheet that connects the interosseous margins of the radius and the ulna. It is the main part of the radio-ulnar syndesmosis, a fibrous joint be ...

, in the interval between the flexor pollicis longus and

, supplying the whole of the former and (most commonly) the radial half of the latter, and ending below in the pronator quadratus and wrist joint. Note that the median nerve supplies all flexor muscles of the forearm except for the ulnar half of

and the flexor carpi ulnaris, which is a superficial muscle of the forearm.

Innervation

The anterior interosseous nerve classically innervates 2.5 muscles: which are deep muscles of the forearm * flexor pollicis longus * pronator quadratus * the radial (lateral) half of

(inserting on the second and third digits) and the inferior radioulnar, wrist and carpal joints.

Injury

A branch of the median nerve, the anterior interosseous nerve (AIN) can be affected by either direct penetrating injury, possibly compression in a fashion similar to carpal tunnel syndrome, but most commonly an idiopathic inflammatory process (referred to an Anterior Interosseous Syndrome). As might be expected, the symptoms involve weakness in the muscle innervated by the AIN including the flexor digitorum profundus muscle to the index (and sometimes the middle) finger, the flexor pollicis longus muscle to the thumb and the pronator quadratus of the distal forearm. AIN also has large sensory nerve to the volar wrist bones and compression of the AIN branch of the median nerve at the elbow can cause referred pain in the volar wrist/distal volar forearm. Non-surgical treatment consists of splinting, proximal tissue massage and anti-inflammatory drugs. Surgical treatment consists of releasing the compression on the nerve from surrounding structures. Pronator Syndrome is similar, but involves both the AIN as well as the median nerve proper.

Clinical significance

Following peripheral nerve injury 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 ...

, the AIN is often used as a donor branch to reinnervate the paralysed muscles innervated by the ulnar nerve.

References

External links

* *
Image (see yellow arrow under "Findings")

Additional Images