Additional Images Innervation Sensory medial branch sensory function to the ulnar half of the dorsal thumb, dorsal index, long, and radial half of the ring finger lateral branch sensory function to the radial dorsal thumb Origin Originates from the radial nerve proper at the level of the radiocapitellar joint. Course Underneath the brachioradialis runs distally in the forearm underneath the brachioradialis, lateral to the radial artery. Forearm deep fascia It pierces the deep fascia of the forearm approximately 7 cm proximal to the radiocarpal joint (9 cm proximal to radial styloid) runs over snuff box to supply dorsal radial surface of hand Terminal branches it then divides into two branches: medial and lateral. Injury & Clinical Conditions Wartenberg's Syndrome