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The radial nerve is a major peripheral nerve of the upper limb that supplies the posterior portion of the upper limb. It has both motor and sensory functions. The radial nerve provides muscular branches that innervate the triceps brachii, anconeus, and brachioradialis muscles. It also gives off sensory branches that innervate the skin of the posterior aspect of the arm and its inferior lateral aspect. The radial nerve is the largest terminal branch of the brachial plexus and is the most commonly injured nerve of the upper extremity.
| Characteristics | Values |
|---|---|
| Type | Peripheral nerve |
| Origin | Brachial plexus |
| Spinal nerve fibres | C5, C6, C7, C8 and T1 |
| Function | Motor and sensory |
| Motor function | Innervates the triceps brachii, anconeus, and brachioradialis muscles |
| Motor function | Innervates muscles in the posterior compartment of the forearm |
| Motor function | Innervates the extensor pollicis brevis, extensor pollicis longus, and abductor pollicis longus |
| Sensory function | Innervates the skin of the upper limb |
| Sensory function | Innervates the skin on the anterolateral arm, distal posterior arm, posterior forearm, and posterolateral wrist and hand areas |
| Sensory function | Innervates the dorsal surface of the lateral three and a half digits |
| Largest branch | Deep branch (motor) |
| Smallest branch | Superficial branch (sensory) |
| Common injury | Humerus fracture |
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What You'll Learn
The radial nerve's role in triceps brachii muscle function
The radial nerve is a major peripheral nerve of the upper limb, supplying the posterior portion of the upper limb. It is the largest nerve of the upper limb and is the most commonly injured nerve of the arm. The nerve has both motor and sensory functions.
The radial nerve innervates the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin. It originates from the brachial plexus, carrying fibres from the posterior roots of spinal nerves C5, C6, C7, C8, and T1. The nerve descends between the deep and superficial extensor muscles and lies on the interosseous membrane.
The radial nerve provides motor innervation to the triceps brachii, which is made up of the long, medial, and lateral heads. The nerve gives out muscular branches to supply these heads of the triceps brachii before and during its course in the radial sulcus. After emerging from the radial sulcus, it supplies other muscles, including the brachialis, brachioradialis, and extensor carpi radialis longus.
The radial nerve also provides sensory innervation to the skin of the arm, forearm, and hand. In the arm, it innervates the skin of the anterolateral arm, distal posterior arm, and posterior forearm. In the hand, it innervates the skin of the posterolateral wrist and hand areas, including the dorsum (back) of the hand, except for the back of the little finger and adjacent half of the ring finger, which are innervated by the ulnar nerve.
Injury to the radial nerve can result in different syndromes with varying motor and sensory deficits. For example, radial nerve tears at the level of the brachial plexus may occur during internal mammary artery dissection and cardiac surgery. Wrist drop is a common presentation of radial nerve palsy, caused by the inability to extend the hand and fingers due to paralysis of wrist and digit extensors.
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Radial nerve injuries and their causes
The radial nerve is a major peripheral nerve that supplies specific parts of the arm, forearm, wrist, and hand. It provides movement to the triceps muscle at the back of the upper arm and contributes to the extension of the wrist and movement and sensation of the wrist, hand, and fingers.
Radial nerve injuries can be caused by direct trauma, prolonged pressure on the nerve, or compression from nearby body structures. Compression can be caused by external factors such as wearing a tight watch band, using crutches improperly, or sleeping or sitting in a way that puts awkward pressure on the upper arm. Compression can also be caused by internal factors, such as abnormal structures like tumours.
Radial nerve injuries can also be caused by repetitive motions that involve grasping and swinging, such as hammering or playing sports like tennis or golf. These activities can damage the radial nerve over time. In addition, systemic conditions such as diabetes, liver dysfunction, kidney dysfunction, and vitamin deficiency can affect the radial nerve.
The most common cause of radial nerve injury is a fracture of the humerus, which can directly damage the nerve or cause damage during the healing process. Iatrogenic radial nerve damage can also occur during certain medical procedures, such as internal mammary artery dissection, cardiac surgery, or upper extremity surgery. Elbow hyperextension, such as when in a supine position for long periods, can also risk radial nerve damage.
Symptoms of radial nerve injury include pain, numbness, and paresthesia, especially in the middle finger, index finger, thumb, back of the hand, and arm. Wrist drop and finger drop may also occur, where there is an inability to extend the wrist, thumb, and fingers.
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The nerve's motor functions
The radial nerve is a major peripheral nerve of the upper limb. It is the largest nerve of the upper limb and is the most commonly injured nerve of the arm. It exits the axilla posterior to the brachial artery and then enters the posterior arm compartment through the triangular interval.
The radial nerve has both motor and sensory functions. The motor function of the radial nerve is to stimulate the posterior arm muscles, posterior forearm muscles, and extrinsic wrist and hand extensors. The radial nerve provides motor innervation to the muscles in the posterior compartment of the forearm, which are mostly extensors. These muscles include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum, extensor indicis, extensor digiti minimi, extensor pollicis longus, extensor pollicis brevis, and abductor pollicis longus.
The deep branch of the radial nerve, also known as the posterior interosseous nerve, provides motor innervation to the muscles in the posterior compartment of the forearm. It pierces the supinator muscle and winds around the radius to reach the posterior of the forearm. The radial nerve also provides muscular branches that innervate the triceps brachii, anconeus, and brachioradialis muscles.
The sensory function of the radial nerve is to supply the skin on the anterolateral arm, distal posterior arm, posterior forearm, and posterolateral wrist and hand areas. The radial nerve provides cutaneous innervation to the skin of the upper limb, including the lateral aspect of the arm, inferior to the insertion of the deltoid muscle, the posterior surface of the arm, and a strip of skin down the middle of the posterior forearm. The superficial branch of the radial nerve, also known as the sensory branch, provides sensation to the thenar eminence and dorsal aspect of the radial 3 and a half digits of the hand.
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The nerve's sensory functions
The radial nerve is a major peripheral nerve of the upper limb that supplies movement and sensory function to the arm, forearm, wrist, and hand. The radial nerve has both motor and sensory functions. The sensory functions of the radial nerve are supplied by its superficial branch, which originates from the cubital fossa. This branch provides cutaneous innervation to the skin of the upper limb, including the lateral aspect of the arm, inferior to the insertion of the deltoid muscle, the posterior surface of the arm, and a strip of skin down the middle of the posterior forearm.
The superficial branch also innervates the dorsal surface of the lateral three and a half digits and the associated area on the dorsum of the hand. This includes the median nerve innervation of the digit pads of the lateral three and a half fingers, while the medial one and a half digit pads are supplied by the ulnar nerve. The sensory branch supplies the skin on the anterolateral arm, distal posterior arm, posterior forearm, and posterolateral wrist and hand areas.
The radial nerve exits the axilla posterior to the brachial artery and then enters the posterior arm compartment through the triangular interval. It wraps around the humerus and passes through the radial tunnel, a narrow opening between bone and muscle at the outside of the elbow. At the elbow, the nerve splits into its superficial and deep branches. The superficial branch provides sensory information to the wrist, hand, and fingers, travelling alongside the radial artery, which supplies blood to the forearm and hand.
The radial nerve can be injured or compressed, leading to pain, numbness, tingling, or a burning sensation. The proximal forearm, where the posterior interosseous branch passes between the supinator heads, is a common compression site. Compression or trauma to the superficial branch can result in cheiralgia paresthetica, a hand neuropathy affecting the dorsum of the hand near the anatomical snuffbox. Radial tunnel syndrome is another uncommon compression neuropathy affecting the radial nerve, typically caused by repetitive forearm movements.
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The nerve's course through the arm
The radial nerve is a major peripheral nerve of the upper limb. It is the largest nerve of the upper limb and is the most commonly injured nerve of the arm. The nerve originates from the brachial plexus, carrying fibres from the posterior roots of spinal nerves C5, C6, C7, C8, and T1.
The radial nerve exits the axilla posterior to the brachial artery and then enters the posterior arm compartment through the triangular interval. The triangular interval is bounded by the triceps brachii's long head medially, the teres major superiorly, and the humerus laterally. In the arm, this posterior cord derivative runs between the triceps' long and medial heads before giving branches to the long and lateral heads of the muscle.
The nerve then continues its course through the arm by passing around the humerus' radial groove together with the profunda brachii (deep brachial) artery. At this level, the radial nerve sends a branch to the medial head of the triceps. At the lateral aspect of the humerus, the nerve pierces the lateral intermuscular septum and then travels anteroinferiorly between the brachialis and brachioradialis at the cubital fossa.
The radial nerve provides muscular branches that innervate the triceps brachii, anconeus, and brachioradialis muscles. It also gives off two sensory branches (posterior brachial cutaneous nerve and lateral inferior cutaneous brachial nerve) that innervate the skin of the posterior aspect of the arm as well as its inferior lateral aspect. Upon entering the cubital region, the radial nerve provides another sensory branch called the posterior antebrachial cutaneous nerve, which innervates a strip of skin down the middle of the posterior forearm.
The radial nerve then terminates by dividing into two branches: a deep branch (motor) and a superficial branch (sensory). The deep branch innervates the muscles in the posterior compartment of the forearm, while the superficial branch contributes to the cutaneous innervation of the dorsal hand and fingers.
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Frequently asked questions
The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It is a major peripheral nerve of the upper limb and is the largest nerve of the upper limb.
The radial nerve innervates the triceps brachii, anconeus, and brachioradialis muscles. It also innervates all 12 muscles in the posterior osteofascial compartment of the forearm, including the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor pollicis brevis.
The radial nerve has both motor and sensory functions. The motor branches stimulate the posterior arm muscles, posterior forearm muscles, and extrinsic wrist and hand extensors. The sensory branches supply the skin on the anterolateral arm, distal posterior arm, posterior forearm, and posterolateral wrist and hand areas.
Injury to the radial nerve can result in different syndromes with varying motor and sensory deficits. One common presentation of radial nerve injury is \"wrist drop", which is caused by the inability to extend the hand and fingers. Sensory deficits may include loss of sensation in the lateral arm, posterior forearm, and dorsum of the hand.
