Lateral antebrachial cutaneous nerve

At a glance

English

Lateral antebrachial cutaneous nerve

Latin (TA2)

Nervus cutaneus lateralis antebrachii

System

Nerve

Region

Upper limb

Side

Paired, left and right

About the lateral antebrachial cutaneous nerve

The lateral cutaneous nerve of the forearm, also called the lateral antebrachial cutaneous nerve, is the terminal branch of the musculocutaneous nerve. Once the parent nerve has supplied the flexor muscles of the arm, it comes out from between biceps brachii and brachialis on the lateral side of the biceps tendon, a few centimetres above the elbow crease. It pierces the deep fascia there and from then on runs in the subcutaneous tissue, passing deep to the cephalic vein. It carries fibres from C5 and C6, with a variable share from C7, and contains no motor fibres.

Near the level of the elbow joint the nerve splits into an anterior (volar) branch and a posterior (dorsal) branch. The anterior branch follows the thumb-side edge of the forearm down to the wrist, supplying skin across the outer half of the front of the forearm. At the wrist it lies superficial to the radial artery; a few fine filaments follow that artery onto the back of the carpus, while the main nerve ends in the skin over the thenar eminence. The posterior branch passes down the posterolateral forearm, supplying the lateral part of its dorsal surface over roughly its lower two-thirds.

The territory overlaps with neighbouring nerves and is joined to them by small communications. The anterior branch connects to the palmar branch of the median nerve and to the superficial radial nerve. The posterior branch links with the superficial radial nerve and with the posterior cutaneous nerve of the forearm. This overlap means that cutting one nerve often leaves a smaller numb area than its full map would suggest.

Because it lies under the cephalic vein at the elbow, the nerve can be injured when blood is drawn or a cannula is placed in the lateral cubital veins, giving burning or numbness along the outer forearm. It can also be pinched at the elbow by the edge of the biceps aponeurosis and tendon during forceful repeated elbow extension with pronation. Its sensory zone is used to test the C6 root and the musculocutaneous nerve in examination of the upper limb.

Course and supply

Arises from

Terminal continuation of the musculocutaneous nerve (C5 to C6, sometimes C7), emerging lateral to the biceps tendon just above the elbow.

Ends in

Ends in anterior and posterior branches that reach the wrist and the skin over the thenar eminence.

Supplies

Purely sensory: supplies the skin of the lateral half of the front of the forearm and the lateral part of its back, down to the wrist and base of the thumb.