radialnerve

The radial nerve is a major peripheral nerve in the upper limb. It originates from the posterior cord of the brachial plexus, which is formed by the posterior branches of the lower three cervical nerves (C5, C6, C7, C8) and the first thoracic nerve (T1). The radial nerve is the largest nerve of the brachial plexus and is responsible for innervating muscles in the posterior compartment of the arm and forearm, as well as providing sensation to a significant portion of the posterior arm, forearm, and dorsum of the hand.

In the upper arm, the radial nerve travels posterior to the humerus, winding through the spiral groove. Here, it gives off branches that supply the triceps brachii muscle, responsible for elbow extension. As it descends into the forearm, the radial nerve divides into two main branches: the deep branch and the superficial branch. The deep branch is primarily motor, innervating the muscles of the posterior forearm, which are responsible for wrist and finger extension. The superficial branch is sensory, providing sensation to the skin of the radial (thumb) side of the dorsum of the hand and the proximal parts of the first three and a half fingers.

Injury to the radial nerve can result in a condition known as "wrist drop," characterized by the inability to extend the wrist and fingers. This can occur due to fractures of the humerus, particularly in the spiral groove, or from prolonged pressure on the nerve, such as from sleeping in an awkward position. Radial nerve palsy can also affect the ability to supinate the forearm. Diagnosis typically involves clinical examination, nerve conduction studies, and electromyography. Treatment depends on the cause and severity of the injury and may include rest, physical therapy, splinting, and in some cases, surgical intervention.