Nerve · Forearm

Lateral antebrachial cutaneous nerve

Nervus cutaneus antebrachii lateralis

What is left of the musculocutaneous nerve once it has finished supplying the muscles of the front of the arm. It emerges from behind the biceps tendon at the elbow crease, pierces the deep fascia and becomes subcutaneous immediately lateral to that tendon — directly beneath the veins on the thumb side of the elbow — then runs down the radial border of the forearm to the wrist and the base of the thumb, dividing into front and back branches on the way. It is the reason a nerve named for muscle ends its life as a skin nerve, and the reason numbness on the outer forearm can point to a problem far higher, in the upper arm.