The radial nerve is a

nerve A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the Electrochemistry, electrochemical nerv ...

in the human body that supplies the posterior portion of the

upper limb The upper Limb (anatomy), limbs or upper extremities are the forelimbs of an upright posture, upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digit (anatomy), digits, including all the musc ...

. It innervates the medial and lateral heads of the

triceps brachii muscle The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, techn ...

and the associated joints and overlying skin. It originates from the

brachial plexus The brachial plexus is a network of nerves (nerve plexus) formed by the anterior rami of the lower four Spinal nerve#Cervical nerves, cervical nerves and first Spinal nerve#Thoracic nerves, thoracic nerve (cervical spinal nerve 5, C5, Cervical spi ...

, carrying fibers from the posterior roots of spinal nerves C5, C6, C7, C8 and T1. The radial nerve and its branches provide motor innervation to the dorsal arm muscles (the

triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

and the anconeus) and the extrinsic extensors of the wrists and hands; it also provides cutaneous

sensory innervation Cutaneous innervation refers to an area of the skin which is supplied by a specific cutaneous nerve. Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve. In some cases, the dermatome is less specific (whe ...

to most of the back of the hand, except for the back of the little finger and adjacent half of the

ring finger The ring finger, third finger, fourth finger, leech finger, or annulary is the fourth digit of the human hand, located between the middle finger and the little finger. Sometimes the term ring finger only refers to the fourth digit of a left-ha ...

(which are innervated by the

ulnar nerve The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or ...

). The radial nerve divides into a deep branch, which becomes the

posterior interosseous nerve The posterior interosseous nerve (or dorsal interosseous nerve/deep radial nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminish ...

, and a superficial branch, which goes on to innervate the dorsum (back) of the hand. This nerve was historically referred to as the musculospiral nerve.

Structure

The radial nerve originates as a terminal branch of the

posterior cord The posterior cord is a part of the brachial plexus The brachial plexus is a network of nerves (nerve plexus) formed by the anterior rami of the lower four Spinal nerve#Cervical nerves, cervical nerves and first Spinal nerve#Thoracic nerves, thor ...

of the

. It goes through the arm, first in the

posterior compartment of the arm Posterior may refer to: * Posterior (anatomy), the end of an organism opposite to anterior ** Buttocks, as a euphemism * Posterior horn (disambiguation) * Posterior probability The posterior probability is a type of conditional probability that ...

, and later in the

anterior compartment of the arm Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

, and continues in the

posterior compartment of the forearm The posterior compartment of the forearm (or extensor compartment) contains twelve muscles which primarily extend the wrist and digits. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna. Struc ...

Arm

The radial nerve originates from the posterior cord of the

with root values of C5 to C8 and T1. From the brachial plexus, it travels behind the third part of the

axillary artery In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit) and the upper limb. Its origin is at the lateral margin of the first rib, before which it is c ...

(part of the axillary artery distal to the

pectoralis minor Pectoralis minor muscle () is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. It arises from ribs III-V; it inserts onto the coracoid process of the scapula. It is innervated by ...

). In the arm, it runs behind the brachial artery and then enters the lower triangular space to reach the radial sulcus on the back of the humerus. It travels downwards together with profunda brachii artery, between the lateral and medial heads of

until it reaches the lateral side the arm at 5 cm below the

deltoid tuberosity In human anatomy, the deltoid tuberosity is a rough, triangular area on the anterolateral (front-side) surface of the middle of the humerus. It is a site of attachment of deltoid muscle. Structure Variation The deltoid tuberosity has been r ...

where it pierces the lateral intermuscular septum to reach the

. Then, it descends down to cross the lateral epicondyle of the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

where the nerve terminates by branching itself into superficial and deep branch which continues into

cubital fossa The cubital fossa, antecubital fossa, chelidon, inside of elbow, or, humorously, wagina, is the area on the anterior side of the upper part between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (antecubit ...

and then into the forearm. The radial nerve gives out muscular branches to supply the long head, medial head, and lateral head of triceps brachii muscles before and during its course in the radial sulcus. After it emerges out from the radial sulcus, it supplies the brachialis,

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...

and extensor carpi radialis longus. Above the radial sulcus, the radial nerve gives off posterior cutaneous nerve of the arm which supplies the skin at the back of the arm. In the radial sulcus, it gives off lower lateral cutaneous nerve of the arm and posterior cutaneous nerve of the forearm. The radial nerve also gives articular branches to supply the elbow joint.

Forearm and hand

In the forearm, it is divided into a superficial branch (primarily sensory) and a deep branch (primarily motor). * The superficial branch of the radial nerve is widely separated from the

radial artery In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm. Structure The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of the ...

in the upper one third of the forearm, closely related to

in the middle third of the forearm, and in the lower third, it descends in the forearm under the tendon of

. It crosses brachioradialis to enter posterior of forearm near the back of the wrist and supply dorsum of hand. It gives sensory supply to dorsal aspect of hand, dorsal aspect of thumb, index finger, middle finger and lateral side of ring finger except the nail beds, which are supplied by proper digital branches of

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

. * The deep branch of the radial nerve (also known as

by some authors)) pierces the

supinator In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius (bone), radius. Its function is to supination, supinate the forearm. Structure The supinator consists of tw ...

muscle, winds around the radius under the cover of supinator to reach posterior of forearm where it again pierces supinator and after which it is known as the

. It pierces the posterior extensor muscles and comes to lie between superficial and deep muscles of the back of the forearm. At the lower border of

extensor pollicis brevis In human anatomy, the extensor pollicis brevis (EPB) is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis belongs to t ...

, it passes deep to the

extensor pollicis longus In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together w ...

and then run on the posterior interosseous membrane. It continues to move along with

posterior interosseous artery The posterior interosseous artery (dorsal interosseous artery) is an artery of the forearm. It is a branch of the common interosseous artery, which is a branch of the ulnar artery. Structure The posterior interosseous artery passes backward bet ...

(a deep branch of

common interosseous artery The common interosseous artery, about 1 cm. in length, arises immediately below the tuberosity of the radius from the ulnar artery. Passing backward to the upper border of the interosseous membrane An interosseous membrane is a thick den ...

which is a branch of

ulnar artery The ulnar artery is the main blood vessel, with oxygenated blood, of the Human Anatomical Terms#Anatomical directions, medial aspects of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins ...

), and ends as a pseudoganglion below extensor retinaculum by supplying the wrist and intercarpal joints.

Variation

It is commonly believed that the radial nerve provides motor innervation to the long head of the

triceps The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the ventral, back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the ...

. However, a study conducted in 2004 found that

axillary nerve The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus ( upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. ...

innervated the long head of the triceps in twenty

cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

s without any supply from the radial nerve.

Function

The following are branches of the radial nerve (including the superficial branch of the radial nerve and the deep branch of the radial nerve/posterior interosseous nerve).

Cutaneous

Cutaneous innervation by the radial nerve is provided by the following nerve branches: *

Posterior cutaneous nerve of arm The posterior cutaneous nerve of arm (internal cutaneous branch of musculospiral, posterior brachial cutaneous nerve) is a branch of the radial nerve that provides sensory innervation for much of the skin on the back of the arm. It arises in the a ...

(originates in axilla) * Inferior lateral cutaneous nerve of arm (originates in arm) * Posterior cutaneous nerve of forearm (originates in arm) The superficial branch of the radial nerve provides sensory innervation to much of the back of the hand, including the web of skin between the thumb and index finger.

Motor

Muscular branches of the radial nerve: *

Triceps brachii The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

* Anconeus *

Brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...

* Extensor carpi radialis longus Deep branch of the radial nerve: *

Extensor carpi radialis brevis In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the ext ...

Supinator In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius (bone), radius. Its function is to supination, supinate the forearm. Structure The supinator consists of tw ...

Posterior interosseous nerve The posterior interosseous nerve (or dorsal interosseous nerve/deep radial nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminish ...

(a continuation of the deep branch after the supinator): * Extensor digitorum *

Extensor digiti minimi The extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected. It arises from the common extensor tendon by a t ...

* Extensor carpi ulnaris * Abductor pollicis longus *

Extensor pollicis brevis In human anatomy, the extensor pollicis brevis (EPB) is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis belongs to t ...

Extensor pollicis longus In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together w ...

Extensor indicis In human anatomy, the extensor indicis (proprius) is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it ext ...

The radial nerve (and its deep branch) provides motor innervation to the muscles in the

and

, which are mostly

extensors In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extend ...

Clinical significance

Injury

Injury to the radial nerve at different levels causes different syndromes with varying motor and sensory deficits. At the axilla * Common mechanisms of injury: Saturday night palsy, crutch palsy,

lesions A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals. Types There is no de ...

* Motor deficit: ** Loss of extension of forearm, weakness of

supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...

, and loss of extension of hand and fingers. ** Presence of wrist drop, due to inability to extend the hand and fingers. * Sensory deficit: Loss of sensation in lateral arm, posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial digits, excluding their nail beds. At mid-arm * Common mechanism of injury: Mid-shaft humeral fracture * Motor deficit: ** Weakness of supination, and loss of extension of hand and fingers. ** Presence of wrist drop, due to inability to extend the hand and fingers. * Sensory deficit: Loss of sensation in posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial digits, excluding their nail beds. Just below the elbow * Common mechanism of injury: Neck of radius fracture, elbow dislocation or fracture, tight cast, rheumatoid nodules, injections due to

tennis elbow Tennis elbow, also known as lateral epicondylitis is an enthesopathy (attachment point disease) of the origin of the extensor carpi radialis brevis on the lateral epicondyle. It causes pain and tenderness over the bony part of the lateral epi ...

, injuring the deep branch of the radial nerve that pierces the radial head, causing

syndrome * Motor deficit: ** Weakness in extension of hand and loss of extension of fingers. ** Presence of finger drop, and partial wrist drop, since the extensor carpi radialis longus and

muscles are working. * Sensory deficit: None, as sensation is supplied by the superficial radial nerve Radial Nerves Extent

Within the distal forearm: * Common mechanism of injury: Wartenberg's syndrome, (not to be confused with Wartenberg's sign), due to nerve entrapment beneath the tendinous insertion of

, tight jewellery, and watch bands. * Motor deficit: None * Sensory deficit: Numbness and tingling in radial half of dorsum of hand, and dorsal aspect of radial digits, excluding their nail beds. * In Wartenberg's syndrome, there is significant radial wrist pain, and close resemblance to symptoms in de Quervain's tenosynovitis. Finkelstein's test may be positive.

History

Additional images

File:Gray413_color.png, Cross-section through the middle of upper arm. File:Gray417_color.PNG, Cross-section through the middle of the forearm. File:Gray525.png, The brachial artery. File:Gray811and813.PNG, Cutaneous nerves of right upper extremity. File:Gray815.png, Superficial palmar nerves. File:Nerves_of_the_left_upper_extremity.gif, Nerves of the left upper extremity. File:Gray817.png, Deep palmar nerves. File:Gray1235 (English).svg, Front of right upper extremity, showing surface markings for bones, arteries, and nerves. File:Gray1236.png, Back of right upper extremity, showing surface markings for bones and nerves. File:Brachial plexus 1.jpg, Radial nerve at newborn File:Radial nerve 3.JPG, Radial nerve File:Radial nerve 2.JPG, Radial nerve File:Slide14yyy.JPG, Radial nerve File:Slide10PPP.JPG, Radial nerve File:Muscles of upper limb.(cross section - human cadaver).jpg, Muscles of upper limb. Cross section.

References

External links

* * - "Axilla, dissection, anterior view" {{Authority control Nerves of the upper limb