Say hello. Bend your wrist. Extend your fingers. You probably could have done that easily. This is because your brain has sent the relevant information to the muscles in your arm, wrist and hand to do so. This transmission has been carried out thanks to a series of nerves, which connect the rest of the nervous system to the muscles. One of them, which is very important for the movement and sensitivity of the extremities, is the radial nerve . It is about this nerve that we are going to talk below.

The radial nerve: description and location

The radial nerve is one of the most important nerve fiber bundles in the control of the upper extremities, being a peripheral nerve of the autonomic nervous system .

It is one of the three main nerves that innervate the upper extremities, along with the ulnar and median nerves .

The radial nerve innervates such relevant muscles as the triceps or the anconeus, or the brachial and brachioradial. Also, among others, the extensor of the fingers, including the index and thumb. It is therefore a nerve of great relevance to the human being. But not only that, it also has connections with the skin nerves and allows sensitivity and tactile perception in the area that innervate.

Areas through which it passes and its two main branches

The nerve in question originates in the brachial plexus, just behind the axillary artery . It then passes through the axilla and then down the arm and forearm, hands and fingers. It should also be noted that there are two radial nerves, one in each half of the body.

It passes through the anterior compartment of the arm, passing around the spiral groove of the humerus (whose rupture could affect the nerve) and then crosses the elbow and reaches the forearm, where it will split into a superficial and a deep branch.

The deep branch passes through the supinator muscle, entering the forearm and reaching the wrist at the back. This branch is linked to muscle perception and the capacity for tension and extension of the innervated muscles.

The superficial branch of the radial nerve acts at skin level, affecting the sensitivity of the upper extremities . This is subdivided into three skin nerves: posterior of the arm, posterior of the forearm and lateral of the arm. It also reaches the hand. This branch allows skin perception of the back of the forearm, the upper arm, the back of the hand and the first four fingers.

Functions of this nerve

Our arms and especially our hands are fundamental elements for the human being since thanks to them we can develop a great amount of activities, from defending ourselves or eating to elaborating tools and complex technologies. Their control is therefore of great importance.

The functions of the radial nerve ine are very broad, and it is interesting that plays a role in both sensory perception and motor control .

On a sensory level, it allows sensitivity and perception of the back of the arm and forearm, including elbows and wrists, as well as part of the hand (specifically, it allows sensitivity of the back of the hand) and most of the fingers (except the little finger and part of the ring finger).

At motor level it allows the extension of the fingers, wrist and arm. Its action is particularly relevant in the posterior forearm , by innervating the muscles of the posterior compartment (which allows the extension of the wrist and fingers) the upper arm (by innervating the brachial triceps).

Radial lesions

Looking at the functions of this nerve in general, it may be easy to guess what effects your injury may have: loss of feeling in much of the back of the arm, the back of the hand and even the fingers and loss of the ability to perform a large number of movements .

If this nerve is injured at the armpit level, the ability to extend the arm, wrist or fingers is lost, leaving the triceps and other innervated muscles paralyzed, as well as the non tactile perception of a large part of the arm and the back of the hand.

If the injury is at the level of the humerus, there will be a decrease in the strength of the triceps and the wrist and fingers will no longer be able to extend and the perception of the back of the hand, wrist and back of the forearm will disappear. This is also called wrist fall, which results in loss of coordination and difficulty in closing the hand.

If the injury is at the level of the superficial branch, the ability to move the entire area will remain intact, but the sensation of the wrist, hand and fingers will be lost.

These alterations can occur due to a great number of factors, and can be produced either by lacerations and lesions, pinching or problems in myelinization . Examples of elements that can cause them are neuropathies such as diabetes, fractures of the humerus or radius, dislocations, intoxication, pressure on the wrist, continuous spell and lack of movement or inflammation.

Bibliographic references:

  • Brazis, P., Biller, J. & Masdeu, J. (Eds) (2007). Peripheral Nerves. In: Localization in Clinical Neurology: 27-72. Philadelphia: Lippincott Williams & Wilkins.
  • Ricci, F.P., Barbosa, R.I., Elui, V.M., Barbieri, C.H., Mazzer, N. & Fonseca, M.C. (2015). Radial nerve injury associated with humeral shaft fracture: a retrospective study. Acta Ortho Bras, 23(1):19-21.