The pudendal nerve is the main nerve of the

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includi ...

. It carries sensation from the

external genitalia A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, a ...

of both sexes and the skin around the anus and perineum, as well as the

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power g ...

supply to various pelvic muscles, including the

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

or female external urethral sphincter and the

external anal sphincter The external anal sphincter (or sphincter ani externus ) is a flat plane of skeletal muscle fibers, elliptical in shape and intimately adherent to the skin surrounding the margin of the anus. Anatomy The external anal sphincter measures about 8 ...

. If damaged, most commonly by childbirth, lesions may cause sensory loss or

fecal incontinence Fecal incontinence (FI), or in some forms encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents, both liquid stool elements and mucus, or solid feces. When this loss includes flatus (gas), it is referre ...

. The nerve may be temporarily blocked as part of an anaesthetic procedure. The

pudendal canal The pudendal canal (also called Alcock's canal) is an anatomical structure in the pelvis through which the internal pudendal artery, internal pudendal veins, and the pudendal nerve pass. Structure The pudendal canal is formed by the fascia of the ...

that carries the pudendal nerve is also known by the eponymous term "Alcock's canal", after

Benjamin Alcock Benjamin Alcock (1801 – 1865) was an Irish anatomist. He is remembered for his description of the pudendal nerve sheath, which came to be known as Alcock's canal, later more usually called the pudendal canal, and an associated disease, Alcock ...

, an Irish anatomist who documented the canal in 1836.

Structure

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 The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor, located posterior to levator ani and anterior to the sacrospinous ligament. Structure The coccygeus muscle is posterior to levator ani and anterior to the sacrospino ...

. 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 The sacrospinous ligament (small or anterior sacrosciatic ligament) is a thin, triangular ligament in the human pelvis. The base of the ligament is attached to the outer edge of the sacrum and coccyx, and the tip of the ligament attaches to the s ...

. The three roots are derived from the

ventral rami The ventral ramus (pl. ''rami'') (Latin for ''branch'') is the anterior division of a spinal nerve. The ventral rami supply the antero-lateral parts of the trunk and the limbs. They are mainly larger than the dorsal rami. Shortly after a spinal ...

of the second, third, and fourth

sacral spinal nerves A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

, with the primary contribution coming from the fourth. The pudendal nerve passes between the

piriformis muscle The piriformis muscle () is a flat, pyramidally-shaped muscle in the gluteal region of the lower limbs. It is one of the six muscles in the lateral rotator group. The piriformis muscle has its origin upon the front surface of the sacrum, and ins ...

and

coccygeus The coccygeus muscle or ischiococcygeus is a muscle of the pelvic floor, located posterior to levator ani and anterior to the sacrospinous ligament. Structure The coccygeus muscle is posterior to levator ani and anterior to the sacrospinous li ...

(ischiococcygeus) muscles and leaves the pelvis through the lower part of the

greater sciatic foramen The greater sciatic foramen is an opening (foramen) in the posterior human pelvis. It is formed by the sacrotuberous and sacrospinous ligaments. The piriformis muscle passes through the foramen and occupies most of its volume. The greater sci ...

. It crosses over the lateral part of the

and reenters the pelvis through the

lesser sciatic foramen The lesser sciatic foramen is an opening (foramen) between the pelvis and the back of the thigh. The foramen is formed by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs ...

. After reentering the pelvis, it accompanies the

internal pudendal artery The internal pudendal artery is one of the three pudendal arteries. It branches off the internal iliac artery, and provides blood to the external genitalia. Structure The internal pudendal artery is the terminal branch of the anterior trunk of ...

and

internal pudendal vein The internal pudendal veins (internal pudic veins) are a set of veins in the pelvis. They are the venae comitantes of the internal pudendal artery. Internal pudendal veins are enclosed by pudendal canal, with internal pudendal artery and pudenda ...

upwards and forwards along the lateral wall of the

ischiorectal fossa The ischioanal fossa (formerly called ischiorectal fossa) is the fat-filled wedge-shaped space located lateral to the anal canal and inferior to the pelvic diaphragm. It is somewhat prismatic in shape, with its base directed to the surface of the ...

, being contained in a sheath of the

obturator fascia The obturator fascia, or fascia of the internal obturator muscle, covers the pelvic surface of that muscle and is attached around the margin of its origin. Above, it is loosely connected to the back part of the arcuate line, and here it is conti ...

termed the

, along with the internal pudendal blood vessels. Inside the pudendal canal, the nerve divides into branches, first giving off the

inferior rectal nerve The Inferior rectal nerves (inferior anal nerves, inferior hemorrhoidal nerve) usually branch from the pudendal nerve but occasionally arises directly from the sacral plexus; they cross the ischiorectal fossa along with the inferior rectal artery ...

, then the

perineal nerve The perineal nerve is a nerve of the pelvis. It arises from the pudendal nerve in the pudendal canal. It gives superficial branches to the skin, and a deep branch to muscles. It supplies the skin and muscles of the perineum. Its latency is t ...

, before continuing as the

dorsal nerve of the penis The dorsal nerve of the penis is the deepest division of the pudendal nerve; it accompanies the internal pudendal artery along the ramus of the ischium; it then runs forward along the margin of the inferior ramus of the pubis, between the superio ...

(in males) or the

dorsal nerve of the clitoris The dorsal nerve of the clitoris is a nerve in females that branches off the pudendal nerve to innervate the clitoris. The nerve is important for female sexual pleasure, and it may play a role in clitoral erections. It travels from below the infe ...

(in females).

Nucleus

The nerve is a major branch of the

sacral plexus In human anatomy, the sacral plexus is a nerve plexus which provides motor and sensory nerves for the posterior thigh, most of the lower leg and foot, and part of the pelvis. It is part of the lumbosacral plexus and emerges from the lumbar verte ...

, with fibers originating in

Onuf's nucleus Onuf's nucleus is a distinct group of neurons located in the ventral part ( laminae IX) of the anterior horn of the sacral region of the human spinal cord involved in the maintenance of micturition and defecatory continence, as well as muscular ...

in the

sacral Sacral may refer to: *Sacred Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property ...

region of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

Variation

The pudendal nerve may vary in its origins. For example, the pudendal nerve may actually originate in the sciatic nerve. Consequently, damage to the sciatic nerve can affect the pudendal nerve as well. Sometimes

dorsal rami The dorsal ramus of spinal nerve (or posterior ramus of spinal nerve, or posterior primary division) is the posterior division of a spinal nerve. The dorsal ramus (Latin for branch, plural ''rami'' ) is the dorsal branch of a spinal nerve that form ...

of the first

sacral nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into th ...

contribute fibers to the pudendal nerve, and even more rarely .

Function

The pudendal nerve has both motor and sensory functions. It does not carry parasympathetic fibers but does carry sympathetic fibers. The pudendal nerve supplies sensation to the

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do n ...

in males, and to the clitoris in females, which travels through the branches of both the

and the

. The posterior

scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...

in males and the

labia The labia are part of the female genitalia; they are the major externally visible portions of the vulva. In humans, there are two pairs of labia: the ''labia majora'' (or the outer labia) are larger and thicker, while the '' labia minora'' are fo ...

in females are also supplied, via the

posterior scrotal nerves The posterior scrotal branches (in men) or posterior labial branches (in women) are two in number, medial and lateral. They are branches of the perineal nerve, which is itself a branch of the pudendal nerve. The pudendal nerve arises from spinal r ...

(males) or

posterior labial nerves The posterior labial nerves are branches of the pudendal nerve. The counterparts in males are the posterior scrotal nerves. See also * Anterior labial nerves The anterior labial nerves are branches of the ilioinguinal nerve. The nerves innervat ...

(females). The pudendal nerve is one of several nerves supplying sensation to these areas., page=Neurovascular Bundles of the Perineum Branches also supply sensation to the

anal canal The anal canal is the part that connects the rectum to the anus, located below the level of the pelvic diaphragm. It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. As the final functional seg ...

. By providing sensation to the penis and the clitoris, the pudendal nerve is responsible for the afferent component of

penile erection An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, ...

and

clitoral erection Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm. Clitoral erection is the result of a complex interaction of psychological, neural, vascular, and endocrine factors, and is usually, though not exclu ...

. It is also responsible for

ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...

. Branches also innervate muscles of the

and the

pelvic floor The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...

; namely, the

bulbospongiosus The bulbospongiosus muscle (bulbocavernosus in older texts) is one of the superficial muscles of the perineum. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis. In femal ...

and the

ischiocavernosus The ischiocavernosus muscle (erectores penis ''or'' erector clitoridis in older texts) is a muscle just below the surface of the perineum, present in both men and women. Structure It arises by tendinous and fleshy fibers from the inner surface of ...

muscles respectively, the

levator ani The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of the ...

muscle (including the

Iliococcygeus The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of t ...

pubococcygeus The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of t ...

puborectalis The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis. It is attached to the inner surface of each side of the ...

and either pubovaginalis in females or puboprostaticus in males) the

(via the inferior anal branch), and

or female external urethral sphincter. 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 Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

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. (Clarification: Unlike the internal sphincter muscle, the external sphincter is made of skeletal muscle, therefore it is under voluntary control of the

somatic nervous system The somatic nervous system (SNS), or voluntary nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles. The somatic nervous system consists of sensory nerves carr ...

Clinical significance

Anesthesia

pudendal nerve block Pudendal anesthesia, also known as a pudendal block, or saddle block, is a form of local anesthesia commonly used in the practice of obstetrics to relieve pain during the delivery of baby by forceps. The pudendal nerve block prevents fainting durin ...

, also known as a ''saddle nerve block'', is a

local anesthesia Local anesthesia is any technique to induce the absence of sensation in a specific part of the body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain, although other local senses may be affected as well. It ...

technique used in an

obstetric Obstetrics is the field of study concentrated on pregnancy, childbirth and the postpartum period. As a medical specialty, obstetrics is combined with gynecology under the discipline known as obstetrics and gynecology (OB/GYN), which is a surg ...

procedure to anesthetize the perineum during

labor Labour or labor may refer to: * Childbirth, the delivery of a baby * Labour (human activity), or work ** Manual labour, physical work ** Wage labour, a socioeconomic relationship between a worker and an employer ** Organized labour and the la ...

. In this procedure, an anesthetic agent such as lidocaine is injected through the inner wall of the

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

about the pudendal nerve.

Damage

The pudendal nerve can be compressed or stretched, resulting in temporary or permanent neuropathy. Irreversible nerve injury may occur when nerves are stretched by 12% or more of their normal length. 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 Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...

), the pudendal nerve is vulnerable to stretch-induced neuropathy.

Pudendal nerve entrapment Pudendal nerve entrapment (PNE), also known as Alcock canal syndrome, is an uncommon source of chronic pain in which the pudendal nerve (located in the pelvis) is entrapped or compressed in Alcock's canal. There are several different types of P ...

, also known as ''Alcock canal syndrome'', is very rare and is associated with professional

cycling Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from t ...

. Systemic diseases such as

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

and multiple sclerosis can damage the pudendal nerve via

demyelination A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This damage impairs the conduction of signals in the affected nerves. In turn, the reduction in conduction ability causes deficiency i ...

or other mechanisms. A pelvic tumor (most notably a large

sacrococcygeal teratoma Sacrococcygeal teratoma (SCT) is a type of tumor known as a teratoma that develops at the base of the coccyx (tailbone) and is thought to be primarily derived from remnants of the primitive streak. Sacrococcygeal teratomas are benign 75% of the ...

), or surgery to remove the tumor, can also cause permanent damage. Unilateral pudendal nerve neuropathy inconsistently causes

in some, but not others. This is because crossover innervation of the external anal sphincter occurs in some individuals.

Imaging

The pudendal nerve is difficult to visualize on routine CT or MR imaging, however under CT guidance, a needle may be placed adjacent to the pudendal neurovascular bundle. The

ischial spine The ischial spine is part of the posterior border of the body of the ischium bone of the pelvis. It is a thin and pointed triangular eminence, more or less elongated in different subjects. Structure The pudendal nerve travels close to the ischia ...

, an easily identifiable structure on CT, is used as the level of injection. A spinal needle is advanced via the

gluteal muscles The gluteal muscles, often called glutes are a group of three muscles which make up the gluteal region commonly known as the buttocks: the gluteus maximus, gluteus medius and gluteus minimus. The three muscles originate from the ilium and sa ...

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 Cortisone is a pregnene (21-carbon) steroid hormone. It is a naturally-occurring corticosteroid metabolite that is also used as a pharmaceutical prodrug; it is not synthesized in the adrenal glands. Cortisol is converted by the action of the enz ...

and local anesthetic to confirm and also treat chronic pain of the external genitalia (known as

vulvodynia Vulvodynia is a chronic pain syndrome that affects the vulvar area and occurs without an identifiable cause. Symptoms typically include a feeling of burning or irritation. It has been established by the ISSVD that for the diagnosis to be made ...

in females), pelvic and anorectal pain.

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. 2 stimulating electrodes and 2 measuring electrodes are mounted on the examiner's gloved finger ("St Mark's electrode").

History

The term pudendal comes from

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

', meaning external genitals, derived from , meaning "parts to be ashamed of". The

is also known by the eponymous term "Alcock's canal", after

, 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 in

Robert Bentley Todd Robert Bentley Todd (9 April 1809 – 30 January 1860) was an Irish-born physician who is best known for describing the condition postictal paralysis in his Lumleian Lectures in 1849 now known as Todd's palsy. Early life The son of physicia ...

's "The Cyclopaedia of Anatomy and Physiology".

Additional images

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

References

External links

* - "Inferior view of female perineum, branches of the internal pudendal artery." * * *
Diagnosis and treatment at www.nervemed.com

www.pudendal.com

{{good article Nerves of the lower limb and lower torso Sexual anatomy