Multiple variations of extensor muscles of forearm in relation to the radial nerve: A case report and review

During routine dissection in the Department of Anatomy, multiple variations of forearm muscles in relation to the radial nerve and its branches were observed on the right side of a 34 year old male cadaver. Brachioradialis close to its origin was receiving muscle fibers from the brachialis and the radial nerve was passing in between them. Extensor carpi radialis brevis was absent and the extensor carpi radialis longus was giving two tendons in the second compartment of extensor retinaculum before its insertion while passing deep to the abductor pollicis longus. Absence of extensor carpi radialis brevis can be explained with the arrangement in lower mammals, where the two extensores carpi radiales are represented by one muscle. Ontogeny repeats phylogeny and anatomical variations have developmental basis. Hence, the pattern of muscular arrangement in this case can be said to be less evolved than the usual, arrangement. The course of radial nerve between the two heads of brachioradialis makes it highly vulnerable to compression and injury, which may manifest as wrist drop (radial nerve palsy) or radial tunnel syndrome (compression of posterior interosseous nerve).