Posterior antebrachial cutaneous nerve

At a glance

English

Posterior antebrachial cutaneous nerve

Latin (TA2)

Nervus cutaneus posterior antebrachii

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the posterior antebrachial cutaneous nerve

Known by several names, including posterior antebrachial cutaneous nerve, this is a sensory branch of the radial nerve. It arises in the back of the arm while the radial nerve lies in the radial groove of the humerus, often from a common stem with the inferior lateral cutaneous nerve of the arm. Its fibres come mostly from C5 to C8.

From its origin the nerve passes outwards through the lateral head of triceps close to where that head attaches to the humerus, and comes to the outer aspect of the arm. It pierces the deep fascia a little below the insertion of the deltoid. In the classical account it gives a smaller upper branch, which runs forwards to the anterior elbow near the cephalic vein and supplies skin of the lower lateral arm, a twig that most modern texts count as the inferior lateral cutaneous nerve of the arm. The main nerve continues down past the lateral elbow and then over the dorsal forearm as far as the wrist.

Along this path it supplies a strip of skin running down the middle of the back of the forearm, from the elbow to the wrist. Near its lower end it joins with the posterior branch of the lateral cutaneous nerve of the forearm, and its edges also meet the posterior branch of the medial cutaneous nerve of the forearm, so the three nerves together cover the dorsal forearm.

Because it leaves the radial nerve high in the arm, the nerve is involved when the radial nerve is damaged in the axilla or in the radial groove, adding a numb strip on the dorsal forearm to wrist drop. Lesions lower down, such as at the elbow or in the forearm, spare it. It may also be injured where it emerges on the outer arm during surgery for humeral fractures or when the radial nerve is explored. The nerve lies near the sites used for some portal incisions in elbow arthroscopy.

Course and supply

Arises from

Radial nerve, in the back of the arm near the radial groove, often with the inferior lateral cutaneous nerve of the arm.

Ends in

Ends in the skin of the dorsal forearm at the wrist, joining the posterior branch of the lateral cutaneous nerve of the forearm.

Supplies

Purely sensory: supplies the skin of the middle of the back of the forearm, and in the classical account part of the lower lateral arm.