Pudendal nerve entrapment (PNE), also known as Alcock canal syndrome, is an uncommon source of

chronic pain Chronic pain is classified as pain that lasts longer than three to six months. In medicine, the distinction between Acute (medicine), acute and Chronic condition, chronic pain is sometimes determined by the amount of time since onset. Two commonly ...

in which the

pudendal nerve The pudendal nerve is the main nerve of the perineum. It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or fem ...

(located in the

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

) is entrapped or compressed in

Alcock's 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 ...

. There are several different types of PNE based on the site of entrapment anatomically (see

Anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...

). Pain is positional and is worsened by sitting. Other symptoms include genital numbness, fecal incontinence and urinary incontinence. The term pudendal neuralgia (PN) is often used interchangeably with "pudendal nerve entrapment". This condition can greatly affect a persons’ quality of life. Pudendal neuralgia can be caused by many factors including inflammation, extreme cycling, and can be a "secondary condition to childbirth". A 2009 review study found both that "prevalence of PN is unknown and it seems to be a rare event" and that "there is no evidence to support equating the presence of this syndrome with a diagnosis of pudendal nerve entrapment," meaning that it is possible to have all the symptoms of pudendal nerve entrapment (otherwise known as pudendal neuralgia) based on the criteria specified at Nantes in 2006, without having an entrapped pudendal nerve. A 2015 study of 13 normal female cadavers found that the pudendal nerve was attached or fixed 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 sp ...

(therefore "entrapped") in all cadavers studied, suggesting that the diagnosis of pudendal nerve entrapment may be overestimated.

Symptoms

There are no specific clinical signs or complementary test results for this condition. Genito-anal

numbness Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to sensory stimuli. In everyday speech this is generally referred to as num ...

fecal Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a relati ...

and/or

urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. It has been identified as an important issue in geria ...

can occur. People may also experience a burning pain in perianal or genital areas. In male competitive cyclists, it is often called "cyclist syndrome", in which cyclists rarely develop recurrent

of 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 ...

and

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 cont ...

after prolonged cycling, or an altered sensation of

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 ...

, with disturbance of

micturition Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

(urination) and reduced awareness of

defecation Defecation (or defaecation) follows digestion, and is a necessary process by which organisms eliminate a solid, semisolid, or liquid waste material known as feces from the digestive tract via the anus. The act has a variety of names ranging f ...

. Nerve entrapment syndromes, presenting as genitalia numbness, are amongst the most common bicycling associated urogenital problems. Pain, if present, is positional and typically caused by sitting and relieved by standing, lying down or sitting on a toilet seat. If the perineal pain is positional (changes with a person's position, for example sitting or standing), this suggests a tunnel syndrome. Anesthesiologist John S. McDonald of

UCLA The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...

reports that sitting pain relieved by standing or sitting on a toilet seat is the most reliable diagnostic parameter. A systematic review study found that PN may be implicated in various sexual dysfunctions such as

persistent genital arousal disorder Persistent genital arousal disorder (PGAD), previously called persistent sexual arousal syndrome, is spontaneous, persistent, unwanted and uncontrollable genital arousal in the absence of sexual stimulation or sexual desire, and is typically not ...

(PGAD),

erectile dysfunction Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...

premature ejaculation Premature ejaculation (PE) occurs when a man expels semen (and most likely experiences orgasm) soon after beginning sexual activity, and with minimal penile stimulation. It has also been called ''early ejaculation'', ''rapid ejaculation'', ''ra ...

, and vestibulodynia. Additionally, another review that looked at cycling-related sexual dysfunction suggested that cycling may indirectly cause sexual dysfunction by disturbing the testosterone signaling aspect of the hypothalamic-pituitary-gonadal axis of the body.

Anatomy

The

carries both motor and sensory

axon An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

s. It stems from the

spinal 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 ...

s S2-S4 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 vertebr ...

. The nerve progresses through the

piriformis The piriformis muscle () is a flat, pyramidally-shaped muscle in the buttock, 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

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 ...

muscles and exits the pelvis by passing through 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 sciati ...

. The pudendal nerve then re-enters the pelvic cavity by passing 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 b ...

. After re-entering the pelvis, it breaks off into three branches known as 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 ...

, 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 test ...

, and then dorsal sensory nerve of the penis or

clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the ope ...

. These three nerves are also referred to as the terminal branches, and they are more susceptible to injuries due to their locations. There are also four levels of Pudendal nerve entrapment compressions: entrapment below the piriformis muscle, entrapment that occurs between the

and

sacrotuberous ligament The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends. Structure It runs from the sacrum (the lower ...

(most common cause), entrapment in the Alcock canal, and entrapment of the terminal branches. Although there has been no evidence for a direct functional connection between the pudendal nerve and sacrotuberous ligament, many clinical studies have pointed at the sacrotuberous ligament as a potential cause of PNE. Around the ischial level of the spine, pudendal nerve runs between the sacrotuberous ligament and the sacrospinous ligament (posteriorly and anteriorly, respectively), giving way for potential compression of the pudendal nerve.

Causes

PNE is said to be caused by genitoanal surgical scarring and mishaps in the pelvic region, trauma to the pelvis,

pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ca ...

, childbirth, bicycling and anatomic abnormalities. Vaginal birth may lead to pudendal nerve damage from the stretch during delivery and the likelihood increases when delivering larger than average babies. As the pudendal nerve lies in the pelvic region, surgical procedures that involve this area, such as a cesarean section, can cause nerve injury. PNE can present in cyclists, likely due to both the compression and stretching of the pudendal nerve for prolonged time. Heavy and prolonged

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

, especially if an inappropriately shaped or incorrectly positioned bicycle seat is used, may eventually thicken the sacrotuberous and/or sacrospinous ligaments and trap the nerve between them, resulting in PNE. Anatomic abnormalities can result in PNE due to the pudendal nerve being fused to different parts of the anatomy, or trapped between the

sacrotuberous The sacrotuberous ligament (great or posterior sacrosciatic ligament) is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends. Structure It runs from the sacrum (the lower ...

and sacrospinalis

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

Diagnosis

Labat et al state that "there are no specific clinical signs or complementary test results of this disease". Kaur et al confirm that there are no specific and consistent radiological findings in patients with PNE. Diagnostic tests that can be performed to suggest PNE are: *

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 ...

s to confirm the pudendal nerve is the source of pain through relief from the procedure. These diagnostic blocks can also be used in place of spinal anesthesia during delivery. * Quantitative sensory threshold testing to detect the inability to sense temperature changes. * High-frequency ultrasonography to identify the location of pudendal nerve compression. * Doppler ultra sound to detect vein compression, a result of nerve compression. * Pudendal nerve terminal motor latency test, an invasive diagnostic test that involves a rectal or vaginal exam. Diagnoses are made through neurophysiological testing rather than imaging. However, MRI and CT imaging may be used to exclude other diagnoses. Similar to a

Tinel's sign Tinel's sign (also Hoffmann-Tinel sign) is a way to detect irritated nerves. It is performed by lightly tapping ( percussing) over the nerve to elicit a sensation of tingling or " pins and needles" in the distribution of the nerve. Percussion is u ...

digital palpation of 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 isch ...

may produce pain. In contrast, people may report temporary relief with a diagnostic pudendal nerve block (see Injections), typically infiltrated near the

. It is important to note that the duration of pain relief from pudendal nerve block is different per person. Imaging studies using MR neurography may be useful. In people with unilateral pudendal entrapment in the

, it is typical to see asymmetric swelling and hyperintensity affecting the pudendal neurovascular bundle.

Nantes Criteria

Pudendal nerve entrapment is difficult to diagnose and there are no specific exams that can clearly confirm the diagnosis. Dr Roger Robert postulated the "Nantes Criteria" to serve as a guide to physicians in diagnosing PNE. It consists of inclusions, exclusions, and complementary characteristics of the syndrome. Some sources discourage the use of this guide due to errors found in the criteria. Inclusion criteria include * Pain is anatomically associated with the pudendal nerve * Pain is mainly experienced when in a sitting position * Pain does not cause nocturnal awakenings * Sensory function is intact * Pudendal nerve block diagnostic test results in pain relief Exclusion criteria include * Imaging results used for exclusion *Unilateral pain *Abnormal diagnostic test results *Pain is acute Complementary criteria include * Nerve pain associated with extreme sensitivity to touch * Described as burning/shooting pain * Posterior pain following defecation A systematic review by Indraccolo et al analyzed PN due to pudendal entrapment and PN without pudendal entrapment in women with chronic pelvic-perianal pain. The review classified the Nantes' criteria as the gold standard for diagnosing PN secondary to PNE. Because of this, the authors of the systematic review additionally suggest that the criteria may be useful in assessing the efficacy and effectiveness of the pudendal nerve entrapment treatments that people may undergo.

Differential diagnosis

Differential diagnosis In healthcare, a differential diagnosis (abbreviated DDx) is a method of analysis of a patient's history and physical examination to arrive at the correct diagnosis. It involves distinguishing a particular disease or condition from others that p ...

should consider the far commoner conditions

chronic prostatitis/chronic pelvic pain syndrome Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), previously known as chronic nonbacterial prostatitis, is long-term pelvic pain and lower urinary tract symptoms (LUTS) without evidence of a bacterial infection. It affects about 2–6% ...

and

interstitial cystitis Interstitial cystitis (IC), a type of bladder pain syndrome (BPS), is chronic pain in the bladder and pelvic floor of unknown cause. It is the urologic chronic pelvic pain syndrome of women. Symptoms include feeling the need to urinate right awa ...

. Other causes for similar symptoms of pudendal nerve entrapment include compression from a tumor, prostatitis in males, uterine diseases in females, complex regional pain syndrome (CRPS), superficial skin infections, and other neuropathies that share the same region as the pudendal nerve.

Treatment

Treatments include behavioral modifications, physical therapy, analgesics and other medications, pudendal nerve block, and surgical nerve decompression. A newer form of treatment is

pulsed radiofrequency Pulsed radiofrequency is the technique whereby radio frequency (RF) oscillations are gated at a rate of pulses (cycles) per second (one cycle per second is known as a hertz (Hz)). Radio frequency energies occupy 1.0 x 104 Hz to 3.0&nb ...

. Most medical treatments are intended for symptomatic relief, such as pain. If symptoms are not managed through this standard of care, surgery is considered.

Nerve protection

This is a form of self treatment to keep pressure off the pudendal nerve. It involves avoiding any activities that may increase pain in the pelvic area. A seat cushion with the center area removed may be used to provide relief and prevent further pain. A 2021 systematic review of preventative and therapeutic strategies found that cyclists who take precautions in maintaining proper posture may prevent the development of a more severe disorder. It is also suggested that using a wider seat when cycling could prevent damage to the nerve, but more evidence is necessary to show long-term benefit.

Physical therapy

Mobilization of the nerves and muscles in the pelvic region is a proposed way to treat symptoms associated with a nerve entrapment. An example of this is neural mobilization. The goal of neural mobilization is to restore the functionality of the nerve and muscles through a variety of exercises involving the lower extremities. Exercises to specifically target the pudendal nerve would be determined based on the anatomical layout of the nerve. It is important to note that evidence is limited to show support for this therapy. Another possible treatment for nerve entrapments in the pelvic region would be stretching and strengthening exercises. A treatment plan would be determined by a physical therapist to specifically manipulate the pudendal nerve through a variety of stretches. Strengthening exercises may also be recommended to relieve the excessive pressure caused by the entrapment, but there is currently limited evidence to support this choice of therapy.

Medications

There are numerous pharmaceutical treatments for

neuropathic pain Neuropathic pain is pain caused by damage or disease affecting the somatosensory system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous ...

associated with pudendal neuralgia. Drugs used include anti-epileptics (like

gabapentin Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is a first-line medication for the treatment of neuropathic pain caused by diabet ...

antidepressant Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, hea ...

s (like

amitriptyline Amitriptyline, sold under the brand name Elavil among others, is a tricyclic antidepressant primarily used to treat cyclic vomiting syndrome (CVS), major depressive disorder and a variety of pain syndromes from neuropathic pain to fibromyalgi ...

), and

palmitoylethanolamide Palmitoylethanolamide (PEA) is an endogenous fatty acid amide, and lipid modulator PEA has been studied in ''in vitro'' and ''in vivo'' systems using exogenously added or dosed compound; there is evidence that it binds to a nuclear receptor, thr ...

. Often times polypharmacy is used with consideration of medication history and side effects.

Injections

One way to identify and alleviate pain associated with the pudendal nerve is a "CT-guided nerve block." During this procedure, "a long-acting local

anesthetic An anesthetic (American English) or anaesthetic (British English; see spelling differences) is a drug used to induce anesthesia ⁠— ⁠in other words, to result in a temporary loss of sensation or awareness. They may be divided into two ...

(

bupivacaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

hydrochloride) and a

corticosteroid Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...

(e.g.

methylprednisolone Methylprednisolone (Depo-Medrol, Medrol, Solu-Medrol) is a synthetic glucocorticoid, primarily prescribed for its anti-inflammatory and immunosuppressive effects. It is either used at low doses for chronic illnesses or used concomitantly at high ...

) are injected to provide immediate pudendal

anesthesia Anesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia (relief from or prevention of pain), paralysis (muscle relaxation), ...

." A pudendal nerve block can be inserted from several different anatomical locations including: transvaginal, transperitoneal, and perirectal. A reduction in pain following this injection is typically felt quickly. The most common side effect of a pudendal nerve block is injection site irritation. Relief from chronic pain may be achieved through this procedure due to the reduced inflammation from the

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

medication, and "steroid-induced fat

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

" which "can reduce inflammation in the region around the nerve" to lessen strain on the pudendal nerve. This treatment may alleviate symptoms for up to 73% of people. Treatment of pudendal nerve entrapment by nerve block is not often prescribed due to "discomfort associated with the local injections as well as the risk of injuring critical structures."

Pulsed radiofrequency

This can be used instead of pudendal nerve perineural injections. In recent years,

Pulsed radiofrequency Pulsed radiofrequency is the technique whereby radio frequency (RF) oscillations are gated at a rate of pulses (cycles) per second (one cycle per second is known as a hertz (Hz)). Radio frequency energies occupy 1.0 x 104 Hz to 3.0&nb ...

(PRF) is starting to become more common for managing chronic pain, and has shown to have long-term benefits and low problem occurrences. Pulsed radiofrequency has also been successful in treating a refractory case of pudendal neuralgia, but additional research is needed to study the effectiveness of pulsed radiofrequency on treating pudendal nerve entrapment. Pudendal Nerve Stimulation (PNS) was found to significantly decrease subjective pain levels in people with pudendal neuralgia. A majority of people who underwent PNS reported "significant" or "remarkable" pain relief at 2 weeks after treatment.

Ergonomics

Various ergonomic devices can be used to allow an individual to sit while helping to take pressure off of the nerve. A few recommendations to decrease nerve compression while cycling include having soft, wide seat in a horizontal position and setting the handlebar height lower than the seat. There are also bicycle seats designed to prevent pudendal nerve compression, these seats usually have a narrow channel in the middle of them. Additionally, other recommendations include wearing padded bike shorts, standing on pedals periodically, shifting to higher gears, and taking frequent breaks. For sitting on hard surfaces, a cushion or coccyx cushion can be used to take pressure off the nerves.

Surgical

Decompression surgery is a "last resort", according to surgeons who perform the operation. It is highly controversial, given that normal cadavers show the pudendal nerve to be "entrapped" and attached, questioning the whole thesis of pudendal nerve entrapment. According to supporters of the theory of PNE, surgery is indicated when severe symptoms are present after exhausting all other forms of treatment. The surgery is also another option to confirm the diagnosis of pudendal nerve entrapment. The surgery is performed by a small number of surgeons in a limited number of countries. The validity of decompression surgery as a treatment and the existence of entrapment as a cause of pelvic pain are highly controversial. While a few doctors will prescribe decompression surgery, most will not. Notably, in February 2003 the

European Association of Urology The European Association of Urology (EAU) is a non-profit organisation committed to the representation of urology professionals worldwide. All active urology professionals, including urology nurses, are eligible for membership of the EAU. The con ...

in its ''Guidelines on Pelvic Pain'' said that expert centers in Europe have found no cases of PNE and that surgical success is rare: There are several different approaches in order to perform a decompression surgery on the pudendal nerve. The different access areas include: superior transgluteal, superior retrosciatic, inferior retrosciatic, medial transgluteal, inferior transgluteal and transischial entry. The transgluteal entry involves "neurolysis of the PN at the infrapiriform canal and transection of the sacrospinal ligament." Another point of entry which is described as a "perineal para-anal pathway", "follows the inferior rectal nerve to the Alcock’s canal." If nerve damage is discovered, other surgery options may be considered like a "

neurectomy A neurectomy is a type of nerve block involving the severing or removal of a nerve. This surgery is performed in rare cases of severe chronic pain where no other treatments have been successful, and for other conditions such as vertigo, involuntary ...

" or "

neuromodulation Neuromodulation is the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. Neuromodulators typically bind to metabotropic, G-protein coupled receptors (GPCRs) to initiate a second ...

References

{{PNS diseases of the nervous system Peripheral nervous system disorders