Radial Tunnel Syndrome

Radial tunnel syndrome refers to a rare compressive neuropathy of the posterior interosseous nerve (PIN) as it passes through the radial tunnel resulting in pain without motor or sensory dysfunction. This pain-only phenomenon is contrasted with PIN compression syndrome, which describes a more severe PIN compressive neuropathy, ultimately causing injury to the large myelin fibers of the PIN resulting in wrist extensor weakness as well as pain. The PIN is a branch of the radial nerve at the elbow and supplies motor innervation to the dorsal extensor compartment of the forearm and sensory fibers to the dorsal wrist capsule. The PIN courses between the two-headed origin of the supinator and around the radial neck posteriorly. It crosses above the abductor pollicis longus (APL) and passes just posterior to the interosseous membrane down the forearm. Its sensory supply to the dorsal wrist capsule is located in the fourth dorsal wrist compartment. The PIN does not provide cutaneous innervation. Of note, radial tunnel syndrome is an entity with much debate with some experts in the field, even questioning its existence.