View source for Radial nerve

{{Short description|Nerve in the human body that supplies the posterior portion of the upper limb}}
{{Infobox nerve
| Name        = Radial nerve
| Latin       = nervus radialis
| Image       = Gray818.png
| Caption     = The [[suprascapular nerve|suprascapular]], [[axillary nerve|axillary]], and radial nerves
| Image2      =
| Caption2    =
| Innervates  = [[Posterior compartment of the arm]], [[posterior compartment of the forearm]]
| BranchFrom  = [[Posterior cord]]
| BranchTo    = [[Posterior interosseous nerve]]
}}
The '''radial nerve''' is a [[nerve]] in the human body that supplies the posterior portion of the [[upper limb]]. It innervates the medial and lateral heads of the [[triceps brachii muscle]] of the arm, as well as all 12 muscles in the [[Posterior compartment of the forearm|posterior osteofascial compartment]] of the [[forearm]] and the associated joints and overlying skin.

It originates from the [[brachial plexus]], carrying fibers from the posterior roots of spinal nerves C5, C6, C7, C8 and T1.<ref name=":0">{{Citation|last1=Scott|first1=Kevin R.|title=Chapter 42 - Rehabilitation of brachial plexus and peripheral nerve disorders|date=2013-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780444529015000423|journal=Handbook of Clinical Neurology|volume=110|pages=499–514|editor-last=Barnes|editor-first=Michael P.|series=Neurological Rehabilitation|publisher=Elsevier|language=en|doi=10.1016/b978-0-444-52901-5.00042-3|access-date=2020-10-25|last2=Ahmed|first2=Aiesha|last3=Scott|first3=Linda|last4=Kothari|first4=Milind J.|pmid=23312667|isbn=9780444529015|editor2-last=Good|editor2-first=David C.|url-access=subscription}}</ref>

The radial nerve and its branches provide [[Motor neuron|motor innervation]] to the dorsal arm muscles (the [[triceps brachii]] and the [[anconeus]]) and the extrinsic extensors of the wrists and hands; it also provides cutaneous [[Nerve supply to the skin|sensory innervation]] to most of the 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]]).

The radial nerve divides into a deep branch, which becomes the [[posterior interosseous nerve]], 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.<ref>{{Cite journal |last1=Colborn |first1=Gene L. |last2=Goodrich |first2=J. Alan |last3=Levine |first3=Monroe I. |last4=Bhatti |first4=Nazir A. |date=1993 |title=The variable anatomy of the nerve to the extensor carpi radialis brevis |url=https://onlinelibrary.wiley.com/doi/10.1002/ca.980060108 |journal=Clinical Anatomy |language=en |volume=6 |issue=1 |pages=48–53 |doi=10.1002/ca.980060108 |s2cid=72093080 |issn=0897-3806|url-access=subscription }}</ref>

==Structure==
[[File:Radial nerve.jpg|thumb|right|300px|Radial nerve of the right axilla, posterior view]]
The radial nerve originates as a terminal branch of the [[posterior cord]] of the [[brachial plexus]].<ref name=":0" /> It goes through the arm, first in the [[posterior compartment of the arm]], and later in the [[anterior compartment of the arm]], and continues in the [[posterior compartment of the forearm]].

===Arm===
The radial nerve originates from the posterior cord of the [[brachial plexus]] with root values of C5 to C8 and T1. From the brachial plexus, it travels behind the third part of the [[axillary artery]] (part of the axillary artery distal to the [[pectoralis minor]]). In the arm, it runs behind the brachial artery and then enters the [[triangular interval|lower triangular space]] to reach the [[radial sulcus]] on the back of the humerus.<ref name=":0" /> It travels downwards together with [[deep artery of arm|profunda brachii artery]], between the lateral and medial heads of [[Triceps|triceps brachii]] until it reaches the lateral side the arm at 5&nbsp;cm below the [[deltoid tuberosity]] where it pierces the [[fascial compartments of arm|lateral intermuscular septum]] to reach the [[anterior compartment of the arm]]. Then, it descends down to cross the lateral epicondyle of the [[humerus]] where the nerve terminates by branching itself into superficial and deep branch which continues into [[cubital fossa]] and then into the forearm.<ref name="BD Chaurasia 2010">{{cite book|last1=Krishna|first1=Garg|title=BD Chaurasia's Human Anatomy (Regional and Applied Dissection and Clinical) Volume 1 - Upper limb and thorax|date=2010|publisher=CBS Publishers and Distributors Pvt Ltd|location=India|isbn=978-81-239-1863-1|pages=95, 111, 122, 128|edition=5th|chapter=8 - Arm}}</ref>

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]] and [[extensor carpi radialis longus]].<ref name="BD Chaurasia 2010"/>

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 [[Joint|articular branches]] to supply the elbow joint.<ref name="BD Chaurasia 2010"/>

===Forearm and hand===
In the forearm, it is divided into a superficial branch (primarily sensory) and a deep branch (primarily motor).<ref>{{Citation |last=Palastanga |first=Nigel |title=Preface |date=1994 |work=Anatomy and Human Movement |pages=viii |url=http://dx.doi.org/10.1016/b978-0-7506-0970-8.50004-6 |access-date=2024-08-23 |publisher=Elsevier |isbn=978-0-7506-0970-8 |last2=Field |first2=Derek |last3=Soames |first3=Roger}}</ref>
* The [[superficial branch of the radial nerve]] is widely separated from the [[radial artery]] in the upper one third of the forearm, closely related to [[radial artery]] in the middle third of the forearm, and in the lower third, it descends in the forearm under the tendon of [[brachioradialis]]. 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]].<ref name="BD Chaurasia 2010"/>
* The [[deep branch of the radial nerve]] (also known as [[posterior interosseous nerve]] by some authors)<ref>{{cite web|title=Acland's video Atlas of Human Anatomy 1.3.1.8 - Radial nerve in the forearm and hand|url=http://aclandanatomy.com/multimediaplayer.aspx?multimediaid=10528121|publisher=Wolters Kluwer|access-date=26 January 2018|archive-url=https://web.archive.org/web/20171129174446/http://aclandanatomy.com/multimediaplayer.aspx?multimediaid=10528121|archive-date=29 November 2017|quote=The deep branch of the radial nerve, also known as the posterior interosseous nerve, is a motor nerve.}}</ref><ref name="Nurul HudaSan2014">{{cite journal|last1=Nurul Huda|first1=Mohd Nor|last2=San|first2=Aye Aye|last3=Fauziah|first3=Othman|title=An Anomalous Pattern of Superficial Branch of Radial Nerve: A Cadaveric Case Report|journal=International Journal of Morphology|volume=32|issue=1|year=2014|pages=29–31|issn=0717-9502|doi=10.4067/S0717-95022014000100005|quote=The deep branch of radial nerve and also known as posterior interosseous nerve is the nerve of extensor compartment of the forearm ...|doi-access=free}}</ref>) pierces the [[supinator]] 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 [[posterior interosseous nerve]]. 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]], it passes deep to the [[extensor pollicis longus]] and then run on the posterior interosseous membrane. It continues to move along with [[posterior interosseous artery]] (a deep branch of [[common interosseous artery]] which is a branch of [[ulnar artery]]), and ends as a [[pseudoganglion]] below [[extensor retinaculum of the hand|extensor retinaculum]] by supplying the wrist and [[intercarpal joint]]s.<ref name="BD Chaurasia 2010"/>

===Variation===
It is commonly believed that the radial nerve provides motor innervation to the long head of the [[triceps]]. However, a study conducted in 2004 found that [[axillary nerve]] innervated the long head of the triceps in twenty [[cadaver]]s without any supply from the radial nerve.<ref name="pmid15365769">{{cite journal |vauthors = de Sèze MP, Rezzouk J, de Sèze M, Uzel M, Lavignolle B, Midy D, Durandeau A |title = Does the motor branch of the long head of the triceps brachii arise from the radial nerve? An anatomic and electromyographic study |journal = Surg Radiol Anat |volume = 26 |issue = 6 |pages = 459–61 |year = 2004 |pmid = 15365769 |doi = 10.1007/s00276-004-0253-z |s2cid = 10052988 }}</ref>

==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===
[[File:Gray812and814.svg|thumb|Cutaneous innervation of the right upper extremity. Areas innervated by the radial nerve are colored in pink.]]
[[Cutaneous innervation]] by the radial nerve is provided by the following nerve branches:
*[[Posterior cutaneous nerve of arm]] (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===
[[File:Gray418.png|thumb|Muscles of the posterior forearm. All the labelled muscles (that is, all the visible muscles except the ones on the dorsal hand and one at top left) are innervated by the radial nerve, and represent all muscles innervated by the radial nerve except for the [[supinator]].]]
[[Muscular branches of the radial nerve]]:
*[[Triceps brachii]] 
*[[Anconeus]]
*[[Brachioradialis]]
*[[Extensor carpi radialis longus]]

[[Deep branch of the radial nerve]]:
*[[Extensor carpi radialis brevis]]
*[[Supinator]]

[[Posterior interosseous nerve]] (a continuation of the deep branch after the supinator):
*[[Extensor digitorum]]
*[[Extensor digiti minimi]]
*[[Extensor carpi ulnaris]]
*[[Abductor pollicis longus]]
*[[Extensor pollicis brevis]]
*[[Extensor pollicis longus]]
*[[Extensor indicis]]

The radial nerve (and its deep branch) provides motor innervation to the muscles in the [[posterior compartment of the arm]] and [[posterior compartment of the forearm|forearm]], which are mostly [[extensors]].

==Clinical significance==
=== Injury ===
[[Radial nerve dysfunction|Injury to the radial nerve]] at different levels causes different syndromes with varying motor and sensory deficits.

'''At the axilla'''
* Common mechanisms of injury: [[Radial neuropathy|Saturday night palsy]],<ref name=":0" /> [[Radial neuropathy|crutch palsy]], [[Lesion|lesions]]<ref>{{Citation|last1=Ryan|first1=Monique M.|title=Chapter 14 – Mononeuropathies|date=2015-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780124170445000147|work=Neuromuscular Disorders of Infancy, Childhood, and Adolescence (Second Edition)|pages=243–273|editor-last=Darras|editor-first=Basil T.|place=San Diego|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-417044-5.00014-7|isbn=978-0-12-417044-5|access-date=2020-10-25|last2=Jones|first2=H. Royden|author-link=Monique Ryan|editor2-last=Jones|editor2-first=H. Royden|editor3-last=Ryan|editor3-first=Monique M.|editor4-last=De Vivo|editor4-first=Darryl C.|url-access=subscription}}</ref>
* Motor deficit:
** Loss of [[Anatomical terms of motion|extension]] of forearm, weakness of [[Anatomical terms of motion|supination]], and loss of extension of hand and fingers.
** Presence of [[wrist drop]], due to inability to extend the hand and fingers.<ref name=":1">{{Citation|last1=Prakash|first1=M. V. S. Satya|title=Chapter 37 - Peripheral Nerve Injuries|date=2016-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780128040751000377|work=Complications in Neuroanesthesia|pages=359–368|editor-last=Prabhakar|editor-first=Hemanshu|place=San Diego|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-804075-1.00037-7|isbn=978-0-12-804075-1|access-date=2020-10-25|last2=Udupi Bidkar|first2=Prasanna|url-access=subscription}}</ref><ref name=":2">{{Citation|last1=Kretschmer|first1=Thomas|title=Chapter 36 - Iatrogenic Injuries of the Nerves|date=2015-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780128026533000853|work=Nerves and Nerve Injuries|pages=557–585|editor-last=Tubbs|editor-first=R. Shane|place=San Diego|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-802653-3.00085-3|isbn=978-0-12-802653-3|access-date=2020-10-25|last2=Heinen|first2=Christian|editor2-last=Rizk|editor2-first=Elias|editor3-last=Shoja|editor3-first=Mohammadali M.|editor4-last=Loukas|editor4-first=Marios|url-access=subscription}}</ref>
* Sensory deficit: Loss of sensation<ref name=":1" /> in lateral arm, posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial {{frac|3|1|2}} digits, excluding their nail beds.

'''At mid-arm'''
* Common mechanism of injury: [[Humerus fracture|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.<ref name=":1" /><ref name=":2" />
* Sensory deficit: Loss of sensation in posterior forearm, the radial half of dorsum of hand, and dorsal aspect of radial {{frac|3|1|2}} 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]], injuring the deep branch of the radial nerve that pierces the radial head, causing [[posterior interosseous nerve]] 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 [[brachioradialis]] muscles are working.
* Sensory deficit: None, as sensation is supplied by the superficial radial nerve[[File:Radial Nerves Extent.jpg|thumb|282x282px|Radial nerve]]

'''Within the distal forearm:'''
* Common mechanism of injury: [[Wartenberg's Syndrome|Wartenberg's syndrome]] (not to be confused with [[Wartenberg's sign]]), due to nerve entrapment beneath the tendinous insertion of [[brachioradialis]], tight jewellery, and watch bands.
* Motor deficit: None
* Sensory deficit: Numbness and tingling in radial half of [[Anatomical terms of location|dorsum]] of hand, and dorsal aspect of radial {{frac|3|1|2}} digits, excluding their nail beds.
* In [[Wartenberg's Syndrome|Wartenberg's syndrome]], there is significant radial wrist pain, and close resemblance to symptoms in [[De Quervain syndrome|de Quervain's tenosynovitis]]. [[Finkelstein's test]] may be positive.<ref>{{cite book|author=Tor Wo Chiu|title=Stone's Plastic Surgery Facts and Figures|year=2011|publisher=Cambridge University Press|isbn=9781139499781}}</ref>

==History==
{{expand section|date=February 2014}}

==Additional images==
{{Cleanup gallery anatomy}}
<gallery>
 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.
</gallery>

==See also==
{{Anatomy-terms}}
* [[Muscular branches of the radial nerve]]
* [[Posterior brachial cutaneous nerve]]
* [[Dorsal antibrachial cutaneous nerve]]
* [[Superficial branch of the radial nerve]]
* [[Deep branch of the radial nerve]]
* [[Radial neuropathy]]
* [[Radial tunnel syndrome]]

==References==
{{Reflist|colwidth=120em}}

==External links==
{{Commons}}
* {{DukeOrtho|Radial_nerve}}
* {{UMichAtlas|hand_plexus}} - "Axilla, dissection, anterior view"

{{Brachial plexus}}
{{Authority control}}

[[Category:Nerves of the upper limb]]