Nerve:  Radial

Compartments:  Posterior of the arm and forearm

Skeletal muscles:  Triceps brachii in the arm; anconeus, supinator, abductor pollicis longus, and extensors carpi ulnaris, carpi radialis longus and brevis, digitorium, indicis, digiti minimi, pollicis longus and brevis in the forearm

Cutaneous distribution:  Skin along the posterior arm, forearm and dorsolateral hand excluding the tips of the digits

Neuromuscular deficit:  Lesions above the elbow proximal to the radial (spiral) groove provoke weakness/paralysis when supinating the forearm and extending the elbow, wrist, and digits 1-5 under resistance. Denervation is accompanied by muscular atrophy, forearm pronation, ‘wrist drop’, digital flexion, and cutaneous deficits along the distribution of the radial nerve in the arm (posterior brachial cutaneous), forearm (posterior antebrachial cutaneous), and hand (superficial cutaneous).

Differential diagnosis:  Lesions occurring below the elbow joint provoke no cutaneous nerve impairment. Motor dysfunction is limited to “wrist drop” and digital flexion resulting from extensor denervation in the forearm (see above).