posterior cutaneous nerve of forearm posterior cutaneous nerve of forearm the posterior cutaneous nerve of forearm is a nerve found in humans and other animals. it is also known as the dorsal antebrachial cutaneous nerve, the external cutaneous branch of the musculospiral nerve, and the posterior antebrachial cutaneous nerve. it is a cutaneous nerve (a nerve that supplies skin) of the forearm. posterior cutaneous nerve of forearmdiagram of segmental distribution of the cutaneous nerves of the right upper extremity. posterior view. ("post. antebrach. cutan." visible in red at right.)detailsfromradial nerveidentifierslatinnervus cutaneus antebrachii posterior, nervus cutaneus antibrachii dorsalista98a14.2.03.052ta26434fma39145anatomical terms of neuroanatomy origin it arises from the radial nerve in the posterior compartment of the arm, often along with the posterior cutaneous nerve of the arm. course it perforates the lateral head of the triceps brachii muscle at the triceps' attachment to the humerus. the upper and smaller branch of the nerve passes to the front of the elbow, lying close to the cephalic vein, and supplies the skin of the lower half of the arm. the lower branch pierces the deep fascia below the insertion of the deltoideus, and descends along the lateral side of the arm and elbow, and then along the back of the forearm to the wrist, supplying the skin in its course, and joining, near its termination, with the dorsal branch of the lateral antebrachial cutaneous nerve.