View source for Pudendal nerve

{{short description|Main nerve of the perineum}}
{{Redirect|Pudendal|the artery or vein|Superficial external pudendal (disambiguation)}}
{{distinguish|text=Inferior pudendal branch of the [[Posterior cutaneous nerve of thigh|Posterior femoral cutaneous nerve]]}}
{{Use dmy dates|date=September 2020}}
{{Infobox nerve
| Name        = Pudendal nerve
| Latin       = nervus pudendus
| Image       = File:Gray542.png
| Caption     = Cross-section of pelvis in which nerve emerges and is visible on the right side.
| Image2      = [[File:Pudendal nerve.svg|class=skin-invert-image|250px]]
| Caption2    = Pudendal nerve, course and branches in a male.
| Innervates  =
| BranchFrom  = [[Sacral nerve]]s S2, S3, S4
| BranchTo    = [[Inferior rectal nerves]]<br />[[perineal nerve]]<br />[[dorsal nerve of the penis]]<br /> [[dorsal nerve of the clitoris]]
}}

The '''pudendal nerve''' is the main [[nerve]] of the [[perineum]].<ref name=Grant2013>{{cite book|author1=AMR Agur |author2=AF Dalley |author3=JCB Grant |title=Grant's atlas of anatomy|year=2013|publisher=Wolters Kluwer Health/Lippincott Williams & Wilkins|location=Philadelphia|isbn=978-1-60831-756-1|url=https://books.google.com/books?id=SmflHHbed4EC&q=%22pudendal+nerve%22&pg=PA274|edition=13th}}</ref>{{rp|274}} It is a [[Mixed nerve|mixed (motor and sensory) nerve]] and also conveys [[Sympathetic nervous system|sympathetic]] [[Autonomic nervous system|autonomic]] fibers. It carries sensation from the [[external genitalia]] of both sexes and the skin around the [[Human anus|anus]] and perineum, as well as the [[Motor neuron|motor]] supply to various pelvic muscles, including the [[external sphincter muscle of male urethra|male]] or [[external sphincter muscle of female urethra|female external urethral sphincter]] and the [[external anal sphincter]].

If damaged, most commonly by childbirth, loss of sensation or [[fecal incontinence]] may result. The nerve may be temporarily anesthetized, called [[pudendal anesthesia]] or pudendal block.

The [[pudendal canal]] that carries the pudendal nerve is also known by the eponymous term "Alcock's canal", after [[Benjamin Alcock]], an Irish anatomist who documented the canal in 1836.

==Structure==

=== Origin ===
[[File:Gray320.png|thumbnail|Image showing the [[greater sciatic foramen]] (large [[foramen]]), and the [[lesser sciatic foramen]], separated by the [[sacrospinous ligament]]. The pudendal nerve exits the pelvis through the greater sciatic foramen, passes over the ligament, and then reenters the pelvis through the lesser sciatic foramen.]]

The pudendal nerve is paired, meaning there are two nerves, one on the left and one on the right side of the body. Each is formed as three roots immediately converge above the upper border of the [[sacrotuberous ligament]] and the [[coccygeus muscle]].<ref name=Grays /> The three roots become two cords when the middle and lower root join to form the lower cord, and these in turn unite to form the pudendal nerve proper just proximal to the [[sacrospinous ligament]].<ref name=Shafik1995 /> The three roots are derived from the [[ventral rami]] of the 2nd, 3rd, and 4th [[sacral spinal nerves]], with the primary contribution coming from the 4th.<ref name=Grays>{{cite book|last=Standring S (editor in chief)|title=Gray's Anatomy: The Anatomical Basis of Clinical Practice|year=2004|publisher=Elsevier|isbn=978-0-443-06676-4|edition=39th|url-access=registration|url=https://archive.org/details/graysanatomyanat0000unse}}</ref><ref name=Moore215>{{cite book|last=Moore|first=Keith L. Moore, Anne M.R. Agur; in collaboration with and with content provided by Arthur F. Dalley II; with the expertise of medical illustrator Valerie Oxorn and the developmental assistance of Marion E.|title=Essential clinical anatomy|year=2007|publisher=Lippincott Williams & Wilkins|location=Baltimore, MD|isbn=978-0-7817-6274-8|edition=3rd}}</ref>{{rp|215}}<ref name=Russell2006>{{cite book|last=Russell RM|title=Examination of peripheral nerve injuries an anatomical approach|year=2006|publisher=Thieme|location=Stuttgart|isbn=978-3-13-143071-7|url=https://books.google.com/books?id=_NxeENi2lVAC&q=%22pudendal+nerve%22&pg=PA157}}</ref>{{rp|157}}

=== Course and relations ===
The pudendal nerve passes between the [[piriformis muscle]] and [[coccygeus]] (ischiococcygeus) muscles and leaves the pelvis through the lower part of the [[greater sciatic foramen]].<ref name=Grays /> It crosses over the lateral part of the [[sacrospinous ligament]] and reenters the pelvis through the [[lesser sciatic foramen]]. After reentering the pelvis, it accompanies the [[internal pudendal artery]] and [[internal pudendal vein]] upwards and forwards along the lateral wall of the [[ischiorectal fossa]], being contained in a sheath of the [[obturator fascia]] termed the [[pudendal canal]], along with the internal pudendal blood vessels.<ref name=ASCRStextbook />{{rp|8}}

=== Branches ===
Inside the pudendal canal, the nerve divides into branches, first giving off the [[inferior rectal nerve]], then the [[perineal nerve]], before continuing as the [[dorsal nerve of the penis]] (in males) or the [[dorsal nerve of the clitoris]] (in females).<ref name=ASCRStextbook />{{rp|34}}

===Nucleus===
The nerve is a major branch of the [[sacral plexus]],<ref name=Brucker2013>{{cite book|author1=TL King |author2=MC Brucker |author3=JM Kriebs |author4=JO Fahey |title=Varney's midwifery|year=2013|publisher=Jones & Bartlett Publishers|isbn=978-1-284-02542-2|url=https://books.google.com/books?id=dbaNAQAAQBAJ&q=%22pudendal+nerve%22&pg=PA950|edition=Fifth}}</ref>{{rp|950}} with fibers originating in [[Onuf's nucleus]] in the [[sacrum|sacral]] region of the [[spinal cord]].<ref name=Shafik1995 />

===Variation===
The pudendal nerve may vary in its origins. For example, the pudendal nerve may actually originate in the [[sciatic nerve]].<ref>{{cite journal|last=Nayak|first=Soubhagya R.|author2=Madhan Kumar, S.J. |author3=Krishnamurthy, Ashwin |author4=Latha Prabhu, V. |author5=D'costa, Sujatha |author6=Jetti, Raghu|title=Unusual origin of dorsal nerve of penis and abnormal formation of pudendal nerve—Clinical significance|journal=Annals of Anatomy - Anatomischer Anzeiger|date=November 2006|volume=188|issue=6|pages=565–566|doi=10.1016/j.aanat.2006.06.011|pmid=17140150}}</ref> Consequently, damage to the sciatic nerve can affect the pudendal nerve as well. Sometimes [[Dorsal ramus of spinal nerve|dorsal rami]] of the first [[sacral nerve]] contribute fibers to the pudendal nerve, and even more rarely {{abbr|S5|fifth sacral nerve}}.<ref name=Shafik1995>{{cite journal|last=Shafik|first=A|author2=el-Sherif, M |author3=Youssef, A |author4= Olfat, ES |title=Surgical anatomy of the pudendal nerve and its clinical implications|journal=Clinical Anatomy|year=1995|volume=8|issue=2|pages=110–5|pmid=7712320 |doi=10.1002/ca.980080205|s2cid=26706414}}</ref>

==Function==
The pudendal nerve has both motor (control of muscles) and sensory functions. It also carries [[Sympathetic nervous system|sympathetic]] autonomic fibers (but not [[Parasympathetic nervous system|parasympathetic]] fibers).<ref name="Kaur2022">{{cite book |last1=Kaur |first1=J |last2=Leslie |first2=SW |last3=Singh |first3=P |title=Pudendal Nerve Entrapment Syndrome. |date=January 2022 |publisher=StatPearls |pmid=31334992 |url=https://www.ncbi.nlm.nih.gov/books/NBK544272/}}</ref><ref>{{cite book|last=Neill|first=editor-in-chief, Jimmy D.|title=Knobil and Neill's physiology of reproduction|year=2006|publisher=Elsevier|location=Amsterdam|isbn=978-0-12-515400-0|edition=3rd}}</ref>{{rp|1738}}

=== Sensory ===
The pudendal nerve supplies sensation to the [[Human penis|penis]] in males, and to the [[clitoris]] in females, which travels through the branches of both the [[dorsal nerve of the penis]] and the [[dorsal nerve of the clitoris]].<ref name="GRAYS2005" />{{rp|422}} The posterior [[scrotum]] in males and the [[labia majora]] in females are also supplied, via the [[posterior scrotal nerves]] (males) or [[posterior labial nerves]] (females). The pudendal nerve is one of several nerves supplying sensation to these areas.<ref name="ORT2007">{{cite book|last=Ort|first=Bruce Ian Bogart, Victoria|title=Elsevier's integrated anatomy and embryology|year=2007|publisher=Elsevier Saunders|location=Philadelphia, Pa.|isbn=978-1-4160-3165-9}}|page=Neurovascular Bundles of the Perineum</ref> Branches also supply sensation to the [[anal canal]].<ref name="ASCRStextbook" />{{rp|8}} By providing sensation to the penis and the clitoris, the pudendal nerve is responsible for the [[Afferent nerve fiber|afferent]] component of [[penile erection]] and [[clitoral erection]].<ref>{{cite book|last=Babayan|first=Mike B. Siroky, Robert D. Oates, Richard K.|title=Handbook of urology diagnosis and therapy|year=2004|publisher=Lippincott Williams & Wilkins|location=Philadelphia, PA|isbn=978-0-7817-4221-4|edition=3rd}}</ref> {{rp|147}}

=== Motor ===
Branches [[innervate]] muscles of the [[perineum]] and the [[pelvic floor]]; namely, the [[Bulbospongiosus muscle|bulbospongiosus]] and the [[ischiocavernosus muscle|ischiocavernosus]] muscles respectively<ref name="ORT2007" /><!-- (As far as I am aware, these last 2 muscles are not classified as pelvic floor muscles... -->, the [[levator ani]] muscle (including the [[Iliococcygeus]], [[pubococcygeus]], [[puborectalis]] and either [[Levator ani#Structure|pubovaginalis]] in females or [[Levator ani#Structure|puboprostaticus]] in males)<ref name="GRAYS2005" />{{rp|422}}<ref>{{cite journal|last=Guaderrama|first=Noelani M.|author2=Liu, Jianmin |author3=Nager, Charles W. |author4=Pretorius, Dolores H. |author5=Sheean, Geoff |author6=Kassab, Ghada |author7= Mittal, Ravinder K. |title=Evidence for the Innervation of Pelvic Floor Muscles by the Pudendal Nerve|journal=Obstetrics & Gynecology|date=October 2005|volume=106|issue=4|pages=774–781|doi=10.1097/01.AOG.0000175165.46481.a8|pmid=16199635|s2cid=20663667}}</ref> the [[external anal sphincter]] (via the inferior anal branch),<ref name="ASCRStextbook">{{cite book|editor=Wolff BG |display-editors=etal |title=The ASCRS textbook of colon and rectal surgery|year=2007|publisher=Springer|location=New York|isbn=978-0-387-24846-2}}</ref>{{rp|7}} and [[external sphincter muscle of male urethra|male]] or [[external sphincter muscle of female urethra|female external urethral sphincter]].<ref name="GRAYS2005">{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell  |author4=illustrations by Richard |author5= Richardson, Paul }}</ref>{{rp|424–425}}

As it functions to innervate the external urethral sphincter it is responsible for the tone of the sphincter mediated via [[acetylcholine]] release. This means that during periods of increased acetylcholine release the [[skeletal muscle]] in the external urethral sphincter contracts, causing urinary retention. Whereas in periods of decreased acetylcholine release the skeletal muscle in the external urethral sphincter relaxes, allowing voiding of the bladder to occur.<ref>{{cite journal | pmc = 2897743 | pmid=18490916 | doi=10.1038/nrn2401 | volume=9 | issue=6 | title=The neural control of micturition | date=June 2008 | journal=Nat. Rev. Neurosci. | pages=453–66 | last1 = Fowler | first1 = CJ | last2 = Griffiths | first2 = D | last3 = de Groat | first3 = WC}}</ref> (Unlike the internal sphincter muscle, the external sphincter is made of skeletal muscle, therefore it is under voluntary control of the [[somatic nervous system]].)

It is also responsible for [[ejaculation]].<ref>{{cite book |last=Penson |first=David F. |title=Male Sexual Function: A Guide to Clinical Management |publisher=Annals of Internal Medicine |year=2002}}</ref>

==Clinical significance==
The pudendal nerve may be tested by elicitation of the [[anocutaneous reflex]] ("anal wink").<ref name="Steele2020">{{cite book |last1=Steele |first1=SR |last2=Maykel |first2=JA |last3=Wexner |first3=SD |title=Clinical Decision Making in Colorectal Surgery |date=11 August 2020 |publisher=Springer International Publishing |isbn=978-3-319-65941-1 |page=5 |language=en}}</ref>

===Anesthesia===
[[File:Saddle anesthesia.png|thumb|Approximate area of "saddle anesthesia" seen from behind (yellow highlight)|419x419px]]
A [[Pudendal anesthesia|pudendal nerve block]], also known as a ''saddle nerve block'', is a [[local anesthesia]] technique used in an [[obstetrics|obstetric]] procedure to anesthetize the perineum during [[childbirth|labor]].<ref>{{cite book|title=Maternal, Neonatal, and Women's Health Nursing, Volume 1|author1=Lynna Y. Littleton |author2=Joan Engebretson |publisher=[[Cengage Learning]]|year=2002|page=727}}</ref> In this procedure, an anesthetic agent such as [[lidocaine]] is injected through the inner wall of the [[vagina]] about the pudendal nerve.<ref>{{cite web |last1=Satpathy |first1=Hemant K. |last2=Fleming |first2=Alfred D. |last3=Fossen |first3=Katie A. |last4=Frey |first4=Donald R. |last5=Macario |first5=Alex |display-authors=1 |editor1-last=Isaacs |editor1-first=Christine |editor2-last=Windle |editor2-first=Mary L. |display-editors=1 |title=Transvaginal Pudendal Nerve Block |url=http://emedicine.medscape.com/article/83078-overview |publisher=WebMD LLC |access-date=19 July 2015}}</ref> Abnormal loss of sensation in the same region as a medical symptom is also sometimes termed [[saddle anesthesia]].

===Damage===
<!-- Causes of dysfunction -->
The pudendal nerve can be compressed or stretched, resulting in temporary or permanent [[neuropathy]]. Injury to the pudendal nerve manifests more as sensory problems (pain or alteration/loss of sensation) rather than loss of muscle control.<ref name="Kaur2022" /> Irreversible nerve injury may occur when nerves are stretched by 12% or more of their normal length.<ref name=ASCRStextbook />{{rp|655}} If the pelvic floor is over-stretched, acutely (e.g. prolonged or difficult childbirth) or chronically (e.g. chronic straining during [[defecation]] caused by [[constipation]]), the pudendal nerve is vulnerable to stretch-induced neuropathy.<ref name=ASCRStextbook />{{rp|655}} After repeated traction of the pudendal nerve, it starts to be replaced by [[fibrous tissue]] with subsequent loss of function.<ref name="Steele2021" /> [[Pudendal nerve entrapment]], also known as ''Alcock canal syndrome'', is [[neuropathic pain]] in the distribution of the pudendal nerve. It is caused by entrapment of the nerve. The condition is estimated to have a prevalence of 1 in 100000,<ref>{{cite book |last1=Chowdhury |first1=SK |last2=Trescot |first2=AM |editor1-last=Trescot |editor1-first=AM |title=Peripheral Nerve Entrapments: Clinical Diagnosis and Management |date=2016 |publisher=Springer International Publishing |isbn=978-3-319-27482-9 |pages=499–514 |url=https://doi.org/10.1007/978-3-319-27482-9_47 |language=en |chapter=Pudendal Nerve Entrapment}}</ref> and is sometimes associated with professional [[cycle sport|cycling]].<ref>{{cite journal |author=Mellion MB |title=Common cycling injuries. Management and prevention |journal=Sports Med |volume=11 |issue=1 |pages=52–70 |date=January 1991 |pmid=2011683 |doi= 10.2165/00007256-199111010-00004|s2cid=20149549 }}</ref> Systemic diseases such as [[diabetes]] and [[multiple sclerosis]] can damage the pudendal nerve via [[demyelinating disease|demyelination]] or other mechanisms.<ref name=ASCRStextbook />{{rp|37}}  A pelvic tumor (most notably a large [[sacrococcygeal teratoma]]), or surgery to remove the tumor, can also cause permanent damage.<ref>{{cite journal|last1=Lim|first1=Jit F.|last2=Tjandra|first2=Joe J.|last3=Hiscock|first3=Richard|last4=Chao|first4=Michael W. T.|last5=Gibbs|first5=Peter|title=Preoperative Chemoradiation for Rectal Cancer Causes Prolonged Pudendal Nerve Terminal Motor Latency|journal=Diseases of the Colon & Rectum|volume=49|issue=1|pages=12–19|doi=10.1007/s10350-005-0221-7|pmid=16292664|year=2006|s2cid=30584236}}</ref>

<!-- Signs and symptoms of dysfunction -->
Unilateral pudendal nerve neuropathy inconsistently causes [[fecal incontinence]] in some, but not others. This is because crossover innervation of the external anal sphincter occurs in some individuals.<ref name=ASCRStextbook />{{rp|34}} There is significant overlap of the innervation of the external anal sphincter from the pudendal nerves of both sides.<ref name="Steele2021" /> This allows partial re-innervation from the opposite side after nerve injury.<ref name="Steele2021" >{{cite book | vauthors = Steele SR, Hull TL, Hyman N, Maykel JA, Read TE, Whitlow CB |title=The ASCRS Textbook of Colon and Rectal Surgery |date=20 November 2021 |publisher=Springer Nature |location=Cham, Switzerland |isbn=978-3-030-66049-9 |edition=4th |language=en}}</ref>

===Imaging===
[[File:CT image guided injection pudendal nerve.png|thumb|Illustration of imaging from a CT-guided injection of the pudendal nerve at the pudendal canal.]]
The pudendal nerve is difficult to visualize on routine [[X-ray computed tomography|CT]] or [[MRI|MR imaging]], however under CT guidance, a needle may be placed adjacent to the pudendal [[neurovascular bundle]].  The [[ischial spine]], an easily identifiable structure on [[X-ray computed tomography|CT]], is used as the level of injection.  A spinal needle is advanced via the [[gluteal muscles]] and advanced within several millimeters of the ischial spine.  Contrast (X-ray dye) is then injected, highlighting the nerve in the canal and allowing for confirmation of correct needle placement.  The nerve may then be injected with [[cortisone]] and local anesthetic to confirm and also treat chronic pain of the external genitalia (known as [[vulvodynia]] in females), pelvic and anorectal pain.<ref>{{cite journal |author=Calvillo O, Skaribas IM, Rockett C. |title=Computed tomography-guided pudendal nerve block. A new diagnostic approach to long-term anoperineal pain: a report of two cases |journal=Reg Anesth Pain Med |volume= 25|issue=4 |pages=420–3 |year=2000 |pmid=10925942 |doi=10.1053/rapm.2000.7620|last2=Skaribas |last3=Rockett |s2cid=1622253 }}</ref><ref>{{cite journal |author=Hough DM, Wittenberg KH, Pawlina W, Maus TP, King BF, Vrtiska TJ, Farrell MA, Antolak SJ Jr. |title=Chronic perineal pain caused by pudendal nerve entrapment: anatomy and CT-guided perineural injection technique |journal=Am J Roentgenol |volume=181 |issue=2 |pages=561–7 |year=2003 |pmid=12876048 |doi=10.2214/ajr.181.2.1810561|last2=Wittenberg |last3=Pawlina |last4=Maus |last5=King |last6=Vrtiska |last7=Farrell |last8=Antolak Jr }}</ref>

====Nerve latency testing====
The time taken for a muscle supplied by the pudendal nerve to contract in response to an electrical stimulus applied to the sensory and motor fibers can be quantified. Increased conduction time (terminal motor latency) signifies damage to the nerve.<ref name=Santoro2010>{{cite book|last=G.A. Santoro, A.P. Wieczorek, C.I. Bartram (editors)|title=Pelvic floor disorders imaging and multidisciplinary approach to management|year=2010|publisher=Springer|location=Dordrecht|isbn=978-88-470-1542-5}}</ref>{{rp|46}} 2 stimulating electrodes and 2 measuring electrodes are mounted on the examiner's gloved finger ("St Mark's electrode").<ref name=Santoro2010 />{{rp|46}}

==History==
The term pudendal comes from [[Latin]] ''{{lang|la|pudenda}}'', meaning external genitals, derived from {{lang|la|pudendum}}, meaning "parts to be ashamed of".<ref>{{cite web|last=Harper|first=Douglas|title=Pudendum|url=http://www.etymonline.com/index.php?term=pudendum&allowed_in_frame=0|work=Online Etymology Dictionary|access-date=28 February 2014}}</ref> The [[pudendal canal]] is also known by the eponymous term "Alcock's canal", after [[Benjamin Alcock]], an Irish anatomist who documented the canal in 1836. Alcock documented the existence of the canal and pudendal nerve in a contribution about [[iliac arteries (disambiguation)|iliac arteries]] in [[Robert Bentley Todd]]'s "The Cyclopaedia of Anatomy and Physiology".<ref>{{cite journal|last=Oelhafen|first=Kim|author2=Shayota, Brian J. |author3=Muhleman, Mitchel |author4=Klaassen, Zachary |author5=Tubbs, R. Shane |author6= Loukas, Marios |title=Benjamin Alcock (1801–?) and his canal|journal=Clinical Anatomy|date=September 2013|volume=26|issue=6|pages=662–666|doi=10.1002/ca.22080|pmid=22488487|s2cid=33298520|doi-access=free}}</ref>

==Additional images==
<gallery>
 File:Gray829.png|The male pelvis, showing the pudendal nerve (centre right)
 File:Grant 1962 214.png|Schematic showing the structures innervated by the pudendal nerve
 File:Grant 1962 215.png|Diagram of the course of the pudendal nerve in the male pelvis
</gallery>

==See also==
{{Anatomy-terms}}
* [[Neurogenic bladder]]
* [[Pudendal neuralgia]]
* [[Sacral plexus]]
* [[Inferior rectal nerve]]
* [[Perineal nerve]]
* [[Dorsal nerve of the penis]]
* [[Dorsal nerve of the clitoris]]
* [[Pudendal canal]]

==References==
{{reflist}}

==External links==
{{Commons}}
* {{SUNYAnatomyFigs|41|04|11}} - "Inferior view of female perineum, branches of the internal pudendal artery."
* {{DartmouthHumanAnatomy|figures/chapter_32/32-2.HTM}}
* {{DartmouthHumanAnatomy|figures/chapter_32/32-3.HTM}}
* {{ViennaCrossSection|pelvis/pelvis-female-17}}
* [https://web.archive.org/web/20080515043137/http://www.nervemed.com/nerve-pudendal.html  Diagnosis and treatment at www.nervemed.com]
* [http://www.pudendal.com  www.pudendal.com]
* [http://www.chronicprostatitis.com/pne.html Pudendal nerve entrapment at chronicprostatitis.com] {{Webarchive|url=https://web.archive.org/web/20141007072510/http://www.chronicprostatitis.com/pne.html |date=7 October 2014 }}
* [http://www.melbourneradiology.com.au/interventional-radiology/nerve-blocks.html CT sequence showing a pudendal nerve block.] {{Webarchive|url=https://web.archive.org/web/20180122072116/http://www.melbourneradiology.com.au/interventional-radiology/nerve-blocks.html |date=22 January 2018 }}

{{Lumbosacral plexus}}

{{Authority control}}

{{good article}}

[[Category:Nerves of the lower limb and lower torso]]
[[Category:Sexual anatomy]]