The main function of the radial nerve is the innervation of the arm, forearm and hand.

Position. The radial nerve is located at the level of the upper limb.

Structure. The radial nerve is an even and mixed nerve, that is, composed of sensory and motor nerve fibers.

Origin. The radial nerve originates from the posterior bundle of the brachial plexus, originating from the cervical vertebrae C5 to C8 and from the thoracic vertebra T11.

Path. The radial nerve passes at the level of the axillary hollow (armpit) and extends along the arm to the elbow, wrapping around the humerus, the sole of the arm. At the elbow, the radial nerve passes in front of the lateral epicondyle and then splits into two branches:

• a deep branch that extends to the posterior surface of the forearm;
• a superficial branch which runs along the lateral edge of the radius to the hand (1).

Innervation. The muscular branches of the radial nerve supply the posterior muscles of the arm and forearm: the triceps brachialis, anconeus, supinator, brachioradialis, radio carpal extensor, extensor carpal ulnar, and some extensor muscles of the fingers. The cutaneous branches of the radial nerve innervate the skin of the upper limb on its posterior and lateral surfaces (1).

Wrist and finger movements. Innervation of the radial nerve allows elbow extension, forearm supination, wrist and finger extension, and thumb abduction (1).

Hand feeling. The radial nerve and its many branches allow the reception and transmission of sensitive information on the posterior surface of the upper limb (1).

Radial nerve involvement. Radial nerve damage can cause pain and / or loss of innervation in the upper limb (2). When the radial nerve is involved, a subject may, for example, feel weakness during elbow extension and supination, have the wrist drooping, or even lose some of the sensitivity of the upper limb. The origins of these conditions are varied and can in particular be:

• compressions of the arm, causing compression of the nerve;
• compressions of the radial nerve by vessels, ganglia, muscles, etc. ;
• tumor compressions due to synovial cysts, lipomas, etc. ;
• fractures of the humerus and radius;
• external trauma to the arm such as a wound.

Physical treatment. Physical therapy, through specific exercise programs, may be prescribed.

Surgical treatment. Surgery may be done to free the radial nerve.

Physical examination. First, a clinical examination is carried out in order to identify and assess the sensory and motor signs perceived by the patient.

Medical imaging exam. An x-ray can be done to confirm or further a diagnosis.

Electrophysiological exploration. The electromyogram makes it possible to study the electrical activity of the radial nerve and to identify potential lesions.

The term “drooping hand” or “gooseneck hand” corresponds to a condition that prevents movement of the wrist and hand. This problem is due to an injury to the radial nerve (1).