Nerve · Upper arm

Inferior lateral cutaneous nerve of the arm

Nervus cutaneus brachii lateralis inferior

A slim skin nerve that the radial nerve gives off while it is still lying in the spiral groove on the back of the humerus, before it emerges into the front of the arm. It pierces the outer head of triceps and supplies the skin of the lower outer arm, taking over exactly where the axillary nerve's patch ends. It is one of three cutaneous nerves the radial nerve sheds along its course, and the arrangement is tidy: this one covers the outer arm below the shoulder, its posterior partner covers the back of the arm, and a third continues down the back of the forearm.