Pudendal Neuralgia

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Continuing Education Activity

Pudendal neuralgia is a chronic pelvic and perineal pain syndrome that originates from damage, injury, inflammation, or irritation of the pudendal nerve. Few providers examine patients specifically for pudendal neuralgia and focus on suspected common morphologic or infectious causes, frequently resulting in delayed diagnosis and treatment. This often manifests as inadequate pain control with subsequent patient frustration, depression, and possibly severe associated negative cognitive, behavioral, sexual, emotional, and psychosocial consequences. Patients with chronic pelvic or perineal pain who are diagnosed with other conditions but fail to respond to standard therapy should be re-evaluated for possible pudendal neuralgia as the treatment protocol is generally totally different and unique. This activity outlines the proper diagnostic evaluation and management of pudendal neuralgia and reviews the role of the interprofessional team in improving care and outcomes for patients with this uncommon but potentially debilitating disorder.

Objectives:

  • Identify the etiology and types of pudendal neuralgia.
  • Describe the appropriate steps in the evaluation of pudendal neuralgia.
  • Review the management options available for pudendal neuralgia.
  • Discuss interprofessional team makeup and strategies for enhancing care coordination and team communication to advance multidisciplinary pudendal neuralgia treatment and improve outcomes.

Introduction

Pudendal neuralgia is the neuropathic pain component of the syndrome caused by pudendal nerve entrapment and neuropathy. It is commonly a bilateral process with a characteristic perineal pain aggravated by sitting, which is present in over 50% of affected patients.[1] The condition is frequently misdiagnosed initially and is often refractory to treatment but can still cause intense, chronic, debilitating pain. 

The pudendal nerve is a mixed nerve having sensory, motor, and autonomic functions. As a result, inflammation or injury to the nerve can cause bladder, bowel, sexual and autonomic dysfunctions, and perineal pain. Pelvic and perineal sensation is more severely affected by injuries than motor or autonomic nerve functions.[2]

The diagnosis is usually made only after many years of painful symptoms, during which time patients have undergone multiple evaluations, medication trials, procedures, interventions, and even surgeries. Symptoms are often treated by end-organ specialists, including gynecologists, colorectal surgeons, pain specialists, and urologists. The condition is significantly underdiagnosed and frequently inadequately or improperly treated, often with a dramatic negative impact on quality of life.[2] This delay in diagnosis and proper treatment can lead to depression and opioid addiction, eventually resulting in confirmed patient suicides in some cases. When properly managed, long-term symptom control is possible and total relief of symptoms has been reported up to 20 years after treatment.

Pudendal neuralgia and pudendal nerve entrapment are largely unknown and unstudied conditions. There is a general lack of quality research or studies on the condition. The information presented here is based on the best available peer-reviewed medical literature and consensus expert opinions.

Etiology

The pudendal nerve is generally composed of fibers from the ventral nerve roots of S2, S3, and S4.[3] The nerve travels anterior to the piriformis muscle, squeezing between it and the coccygeus muscle through the greater sciatic foramen and between the sacrotuberous and sacrospinous ligaments.[2][4] The net effect is analogous to a "clamp" or "lobster claw," pinching or impinging on the nerve.[4] Upon leaving this site, the nerve travels through Alcock's canal (also known as the pudendal canal). It divides into the deep and superficial perineal nerves, the dorsal nerve of the penis or clitoris, and the inferior rectal nerve. Many variations in the nerve structure have been noted during surgery and anatomical dissections.

Four common sites of pudendal nerve entrapment are described.[2] These include the following: (See our companion article on Pudendal Nerve Entrapment Syndrome.)[2]

  • Type I -  Entrapment below the piriformis muscle as the pudendal nerve exits the greater sciatic notch.
  • Type II - Entrapment between sacrospinous and sacrotuberous ligaments (this is the most common cause of pudendal nerve entrapment).
  • Type III- Entrapment within Alcock's canal.
  • Type IV - Entrapment of terminal branches only. (Inferior rectal nerves, superficial and deep perineal nerves, and the dorsal nerve of the penis/clitoris.)

Bony remodeling in the pelvis occurs commonly and is related to repetitive use and overuse of pelvic floor muscles. This causes changes in the ischial spine and the inferior lateral angle of the sacrum. When untreated, pudendal neuropathy progresses from minor symptoms, often beginning with bladder complaints, to more generalized and painful symptoms as nerve damage advances. Severe pain may occur in many sites and is often confused with various morphologic/organ diseases. The pain tends to be chronic and can be severe enough to be disabling. 

Pudendal neuralgia is generally a "tunnel" syndrome, typically resulting from cumulative, repetitive microtrauma to the nerve. However, it can also be caused by indirect trauma, viral infections (such as HIV and Herpes Zoster), multiple sclerosis, and diabetes.[5]

Common causes include:

  • Prolonged sitting (e.g., seamstresses, computer operators, office workers, judges, concert pianists, commercial drivers, chess players, locomotive engineers)[1][2]
  • Repetitive hip flexion (sports activities, exercising, jogging, cycling)[5][6]
  • Direct trauma including falls, motor vehicle accidents, and pelvic surgeries, especially when using mesh in pelvic organ prolapse repairs[7][8][9]
  • Radiation therapy, especially in males treated for prostate cancer as well as patients treated for rectal and gynecological cancers[2]
  • Childbirth injuries from stretching of the pelvic musculature from the fetal head[10][11] 
  • Chronic constipation [2]

Infrequent causes include:

  • Benign tumors and metastatic lesions to the nerve pathway and herpes simplex infections

Stress is not causal but may be a potent aggravator of neuropathic pain.

Epidemiology

Pudendal neuralgia is often unrecognized, so the true incidence is unknown.[12] The International Pudendal Neuropathy Association estimates 1 in 100,000 of the general population.[12] Spinosa et al. document the incidence of pudendal neuralgia at 1% in the general population, affecting women more than men but it is found in both genders and also occurs in children due to congenital anomalies in the nerve pathway.[13] 

Orphanet, a European health information database, states pudendal neuralgia affects 4% of all patients undergoing consultations for pain control and affects seven women for every three men.[14] Many providers, especially those that routinely treat pudendal neuralgia, believe the actual incidence rates are significantly higher than stated in the existing literature.[12]

Pathophysiology

The compression of the pudendal nerve(s) is visible to the surgeon during decompression and transposition surgeries. The degree of compression may be severe. Congenital nerve compression is frequently noted when aberrant fascias are present, and the nerve travels through the sacrotuberous ligament. Acquired compressions include scarring after pelvic surgeries and suspected hematomas following repetitive serious falls, as in skiers, skaters, snowboarders, and other athletes. It is particularly common in cyclists.

A hypertrophied obturator internus muscle may compress the nerve in the pudendal canal. A dense, enlarged falciform process is seen in some athletes. Stretching of the nerve(s) is occasionally observed. 

History and Physical

Pudendal neuralgia should be suspected in all patients with a history of pelvic pain (especially perineal and genital) with or without concurrent sexual, bladder, or bowel symptoms. The onset of pain is usually subtle, except when caused by acute trauma. Pain is generally less in the morning and progresses throughout the day. Patients frequently complain of burning perineal pain and may also experience tingling, aching, stabbing, and electric shock-like discomfort.[15] In over 50% of patients, pain is exacerbated while sitting and relieved when standing, lying down, or seated on a toilet.[5] There may also be referred sciatic pain, medial thigh pain (indicating obturator nerve involvement), pain after ejaculation, worsening discomfort after intercourse, and erectile dysfunction.

Paroxysmal pain, associated with pruritus or located exclusively in the coccygeal, gluteal, hypogastric, or pubic areas (outside the sensory distribution area of the pudendal nerve) is unlikely to be from pudendal neuralgia.[16]

Patients with pudendal neuralgia typically complain of chronic perineal pain, although they may also present with bowel, bladder, and sexual issues with or without discomfort. Pain distribution may be limited to the perineum or extensive and may include the vulva, vagina, clitoris, perineum, and rectum in females; the glans penis, scrotum, perineum, and rectum in males.[1] Coccygeal pain and pain referred to the calf, foot, and toes are also frequent complaints. Contact with clothing may cause pain or discomfort (known as allodynia). This is an indicator of central sensitization. A foreign body sensation in the vagina or rectum may also be present.[15] This pelvic foreign body sensation, described as sitting on a golf ball or a hot poker in the rectum, indicates central sensitization. Pain may also be felt outside the 'territory' of the pudendal nerve innervation and may include vague, neuropathic pain in the lower abdomen, posterior and inner thigh, or lower back.[16] 

Areas affected by the sensory portion of the pudendal nerve include: 

  • The lower buttocks
  • The area between the buttocks and genitals (perineum)
  • The area around the anus and rectum
  • The vulva, labia and clitoris in women
  • The scrotum and penis in men

Other symptoms associated with pudendal neuralgia may include urinary frequency, urgency, symptoms mimicking interstitial cystitis, painful ejaculation, dyspareunia, painful nocturnal orgasms, and persistent sexual arousal.[17] Patients should be asked about activities involving repetitive hip flexion, prolonged sitting, falls, and alleviating/aggravating factors that may suggest the diagnosis of pudendal neuralgia.

Physical Exam

It is essential in both genders to test each pudendal nerve branch for pinprick sensation, including the glans/clitoris, posterior scrotum (labia), and posterior anal skin bilaterally.[18] One or more of the six branches may show hyperalgesia, hypoalgesia, or analgesia using the thigh as the control. A visual examination will rule out obvious lesions in the vulva, perineal, male genital, or rectal areas. The testis, epididymis, and vas deferens should be examined for tenderness. The rectal sphincter should be evaluated, and any tender regions of the anal canal (e.g., anal fissures) should be inspected. The pelvic floor and the obturator internus muscles should be softly palpated to evaluate for muscle spasms and tenderness. The prostate examination should include an evaluation of the expressed prostate secretions (EPS) or a post-massage urinalysis for inflammatory cells.[19] 

It is most important to palpate the pathway of the pudendal nerve medial to the ischial spine and over Alcock's canal. When palpation of these sites reproduces pain in the pudendal distribution, it indicates a "mid-nerve" injury called the Valleix phenomenon. It is considered diagnostic of a mid-nerve pudendal injury and is analogous to the Tinel sign in carpal tunnel syndrome.[20] 

In females, the examination is similar and includes gentle palpation of the uterus/ovaries. On bimanual examination, pressure should be placed over the T12 abdominal cutaneous and the iliohypogastric nerves, which may be misinterpreted as organ pain. Other peripheral mononeuropathies are common in pudendal neuropathy patients. These include abdominal cutaneous neuropathies, ilioinguinal and iliohypogastric neuropathies, the thoracolumbar junction syndrome or Maigne syndrome, neuropathies of the T12 posterior ramus, posterior cutaneous perforating nerve, middle cluneal neuropathies of S2, S3, S4, and neuropathy of the posterior femoral cutaneous nerve-perineal branch. Genitofemoral, obturator, lateral primary cutaneous, and inferior cluneal neuropathies should also be considered.

Evaluation

Pudendal neuralgia is initially a clinical, "bedside" diagnosis that is suggested by typical symptoms, sometimes referred to as the "Nantes" criteria, which include:[15][16]

  • Perineal pain that worsens on sitting but is relieved on lying, standing, or sitting on the toilet
  • Pain does not wake the patient at night                   
  • No specific sensory deficit on neurological examination
  • Confirmation by positive neurophysiological testing and/or a successful diagnostic pudendal nerve block injection

Imaging techniques do not significantly help make a diagnosis. Abdominal and pelvic CT scans are helpful only for exclusion purposes and for image-guided nerve blocks, which are recommended.[21] MRIs of the lumbosacral spine and the pelvis are useful for diagnostic exclusions and are often recommended. They should definitely be done before surgical interventions.[15]

Neurophysiological tests have been useful in the workup of pudendal neuropathy and neuralgia.

  • Compressed nerves lose the ability to quickly transmit thermal and vibratory sensory changes.[22] Quantitative warm thermal threshold sensitivity testing is the easiest and most commonly performed neurosensory test for possible pudendal neuropathy.[23] 
  • Warm sensory threshold detection testing is performed by placing a probe in the innervated area of concern, and the probe's temperature is slowly raised. Patients with neuropathy cannot detect gradual temperature changes and only react when the probe temperature is high enough to cause pain. Several devices (the NTE–2 and TSA 2 thermosensory testers and the MSA thermal stimulator) are commercially available, non-invasive, and easily used in a physician's office.[24] 
  • Biothesiometry, which uses a probe with variable vibratory intensity, can be used similarly to identify vibratory sensory thresholds, but warm sensory threshold detection is easier and more commonly performed. 
  • The pudendal nerve terminal motor latency test (PNTML) has been used for diagnosis and monitoring treatment results.[25] The pudendal nerve terminal motor latency test measures motor function in the inferior rectal nerve. It can be performed in the physician's office but is somewhat invasive, requiring a rectal or vaginal examination. A surface St. Mark electrode provides stimuli at the ischial spine, and the speed of travel or latency time is measured at the anal sphincter. Axonal damage and demyelination can both be identified. Postoperative normalization of the pudendal nerve terminal motor latency has been measured following decompression surgery in women with stress urinary incontinence.
  • Intraoperative neurophysiologic testing is often performed during the decompression of the pudendal nerve. Other motor nerve tests include bulbocavernosus reflex and latency testing. Although electromyography (EMG) may complement the diagnosis, patients often find it a more painful and unpleasant experience compared to pudendal nerve terminal motor latency and warm sensory threshold detection testing.
  • Perineal electroneuromyography can be useful but is not considered specific enough to be a recommended part of the routine diagnostic evaluation.[15]
  • Somatosensory evoked potential (SSEP) testing has been used to confirm pudendal neuropathy. SSEP is also a valuable tool to identify and limit pudendal nerve damage caused by compression of the perineum due to traction during hip surgeries.[26][27]
  • It should be noted that stimuli from the neurophysiologic testing often reproduce indicators of central sensitization (e.g., pain in a toe from a stimulus to the labium or contralateral inguinal pain during pudendal nerve terminal motor latency testing).

Many experts have recommended pudendal nerve block injections as a diagnostic tool, but there is a lack of high-quality studies to validate this technique.[15][28] The recommended procedure is to inject a short-acting local anesthetic under image guidance (CT, ultrasound, or fluoroscopy) into the sacrospinous ligament. This is done where the pudendal nerve enters the lesser sciatic foramen, about 1 cm inferior and medial to the ischial attachment of the sacrospinous ligament.[29] The precise location of the block is often aided by patient statements or pudendal symptoms when the needle is inserted. While primarily a transperineal procedure in men, it can also be performed transvaginally in women. A perirectal and a transgluteal approach have also been described.[30][31]

The patient should be actively experiencing significant pain at the time of the diagnostic injection. The patient is asked to quantify and record their pain level immediately before, during, and for two hours after the injection. A skin pin-prick test may be used to ascertain skin sensitivity. An immediate reduction in pain of 50% or more is considered a positive test result. The use of image guidance, usually with CT or ultrasound, helps make the use of pudendal nerve blocks a much more reliable diagnostic tool.[15][29][32]

Injections may also be given directly into Alcock's canal, but these are generally considered most useful to indicate if the patient is a potential candidate for surgical decompression.[15] (Alcock's canal can be identified using contrast.) 

Up to 20% of diagnostic pudendal nerve blocks may be of poor technical quality and fail to provide substantial pain relief even in confirmed cases.[33] Therefore, only 80% of patients would be correctly diagnosed with pudendal neuropathy in this way. This is often due to physician inexperience or lack of training.[34] Moreover, patients with organ symptoms but without pain would be excluded from having their diagnosis made by this modality. Anesthesia is typically achieved within 5 minutes of a successful block achieving maximum effect after 10 to 20 minutes if a short-acting local anesthetic agent is used. The use of image guidance, usually with CT or ultrasound, helps make the use of pudendal nerve blocks more reliable.[15][32] Note that a successful pudendal nerve block will anesthetize the lower vagina and vulva, scrotum and penis, the posterior perineum, and anus but does not eliminate sensation in the anterior perineum where branches of the ilioinguinal and genitofemoral nerves supply sensory input. Pudendal blocks will not affect sensation in the cervix or upper vagina and are not effective for pain control involving uterine manipulations.[35] 

Complications are rare but may include pain and infection at the injection site, bleeding, hematoma, direct pudendal nerve damage, and reactions if the injection is inadvertently given intravascularly.[29] (See our companion article on Pudendal Nerve Blocks for more details on the procedure.)[29]

Treatment / Management

Patients with pudendal neuralgia are typically diagnosed after several years of symptoms, have seen multiple physicians, and have often undergone extensive, repetitive testing. They may have had several surgeries and are often told: "it is in your head." Patients often suffer anxiety or depression and may initially be resistant to new treatments or evaluations. Patients may become angry, frustrated, or feel threatened if their standard therapy, such as opioids, is questioned or modified.[36] Referral to an experienced psychologist should be considered for emotional support as treatment progresses. At any time during treatment and even after a long-term 'cure,' stress may precipitate or aggravate the pain.

As pudendal neuropathy is often a tunnel entrapment syndrome, it is treated in a manner somewhat analogous to carpal tunnel syndrome, namely:

  • Conservative nerve protection measures initially, along with physical therapy and medications
  • Pudendal nerve block perineural injections are given monthly as needed or as a series of three at four-week intervals
  • If conservative treatments fail, sacral neuromodulation and/or surgical decompression of the pudendal nerve(s) should be considered

The monitoring of responses can be objective when using symptom scores. Experience has shown that the National Institutes of Health - Chronic Prostatitis Symptom Index or NIH-CPSI is an excellent metric useful in both genders with simple changes of anatomical terms.[37] The American Urological Association Symptom Score Index (AUASI) is also beneficial for monitoring patients experiencing urinary symptoms. (This is also called the International Prostate Symptom Score (IPSS).) This symptom score index has been validated in both genders and is widely available in multiple languages.[38]

Initial Conservative Measures

Initial conservative measures are designed to help protect the nerve and avoid any aggravation of the neuropathy. When pain occurs while seated, a simple "sit-pad" or "doughnut" that can be self-constructed or purchased commercially. With the center section of the seating pad removed, the perineum has no pressure, and the patient is sitting on his/her ischial tuberosities. These pads are useful and may even be curative in some cases. Avoidance of sitting should be recommended, such as the use of a standing workstation., Cessation of hip flexion exercises, cycling, jogging, rowing, and similar sports activities are essential to prevent repeated pudendal nerve injury. About 20% to 30% of patients report improvement with conservative measures and lifestyle modifications.

Medications

Polypharmacy is often necessary to control the multiple symptoms of neuropathic pain and common central sensitization in pudendal neuralgia patients.[15] Control of ectopic firing from the injured nerve and the dorsal ganglion can be achieved with various drugs, including antibiotics, tricyclic amines, central-acting sympatholytic medications, and others. Close monitoring is necessary with changing medications depending on treatment response and side effects. No prospective, randomized studies are available to indicate which medications or combinations are most effective or useful for pudendal neuralgia. Based on general neuropathic pain studies, initial therapies usually include amitriptyline, a selective serotonin-norepinephrine reuptake inhibitor (SSNRI) antidepressant such as duloxetine, and/or an anti-epileptic such as gabapentin and/or pregabalin.[15][39][40] Gabapentin and pregabalin are both analogs of the neurotransmitter gamma-aminobutyric acid, but pregabalin is more potent, has greater bioavailability, and is absorbed quicker, which leads to fewer side effects.[41]

Several medications are commonly used for pudendal neuralgia.[15] These include:

  • Amitriptyline is often started at 10 mg HS, titrating every five days to a maximum of 50 mg HS as tolerated.
  • Duloxetine is started at 30 mg daily for one week; then, the dose is increased to 60 mg daily. No additional benefit is noted from increasing the dose further.
  • Gabapentin is often started at 300 mg TID (titrated up to 900 mg TID) and/or pregabalin starting at 75 mg BID up to a maximum of 300 mg BID.
  • Clonidine 0.1 mg HS can be beneficial in controlling sympathetically moderated pain. Patients often find this is also a very useful sedative for sleep.
  • Antihistamines may have a beneficial adjuvant effect.
  • Compounded topical creams containing gabapentin, ketamine, and clonidine may be useful.
  • Ketamine oral troches and nasal spray may be necessary when pain is unrelenting.

Combining medication types is often necessary to control symptoms.[15] The choice of drugs to be used must consider the patient's medical history, prior usage of medications, side effects, comorbidities, drug effectiveness, possible interactions, and potential risk of addiction. Opioids should be avoided if possible.

Cognitive behavioral therapy has not been specifically tested for pudendal neuralgia but has been helpful for other types of neuropathic pelvic pain, such as dyspareunia and vulvar vestibulitis (a type of vulvodynia).[42][43] Cognitive behavioral therapy is generally recommended as a complementary or adjunctive therapy in pudendal neuralgia patients who also demonstrate any psychological effects associated with chronic pain such as anxiety, melancholia, depression, hypervigilance, kinesiophobia, post-traumatic stress disorder, perfectionism, mood fluctuations, emotional instability, altered cognition, hopelessness, sense of injustice, sexual dysfunction or lack of motivation for change.[15][44] A 2016 review of 1024 chronic pain patients found that about 34% had severe depression and almost 61% had probable depression.[45] Additionally, chronic pain tends to substantially increase total health care costs for those individuals.[45][46]

Physical therapy may be a useful adjunct for tender, spastic pelvic floor musculature. Most patients should use it for at least 6 to 12 weeks. Physical therapy appears to be most helpful for levator ani syndrome or similar myofascial syndromes involving the lateral rotator group (obturator internus and piriformis muscles).[15] Muscle relaxing treatments are generally preferred. While most experts generally recommend physical therapy, there is a lack of adequately performed studies to validate its efficacy definitively.[47][48][49][50]

Transcutaneous electrical nerve stimulation (TENS) has been used with reasonable success for pelvic pain syndrome, perineal discomfort, and prostatodynia, although there is very limited data on its use specifically for pudendal neuralgia.[15] Experience with TENS for various pelvic and perineal pain syndromes strongly suggests it can be helpful for pudendal neuralgia.[51][52][53] Adding TENS treatment to standard physical therapy has shown a benefit in reported symptomatic relief compared to physical therapy alone.[54] However, there is no standardization on TENS therapy for pelvic pain or pudendal neuralgia with a great variety of techniques, protocols, treatment durations, electrical frequencies used, type, size, and location of the electrodes, being reported.[15] In a 2017 study by Sharma et al. of 120 chronic pelvic and perineal pain patients with no identifiable underlying cause, all the patients treated with TENS showed improvement, with the greatest benefit in those receiving the highest tested frequency of 75 Hz to 100 Hz.[52] 

Several patterns of TENS electrode placements have been recommended. These include along the tibial or sacral S2-4 nerve roots as well as direct perineal stimulation with circular penile or vulvar electrodes.[15] Since the treatment is safe, widely available, relatively inexpensive, non-invasive, easily incorporated into existing physical therapy protocols, and appears to be at least somewhat effective, it is not unreasonable to consider adding TENS therapy to other conservative treatments, but there is insufficient data to make it a first-line therapy at this time.[15]

Pudendal nerve block injections are a mainstay for diagnosing pudendal neuralgia, but their role in therapy is less clear. Like most of the available treatments for pudendal neuralgia, there is a lack of high-quality prospective, randomized trials demonstrating efficacy and no consensus on the optimal medications, preferred protocols, or the long-term value of repeated injections.[15]

Short-acting local anesthetics are used for diagnostic pudendal nerve block testing but for therapeutic injections; there is no definitive recommended agent. Both local anesthetics and corticosteroids have been used separately or together with roughly similar results. A combination of short and long-acting local anesthetics together with steroids has the theoretical advantage of both immediate and long-lasting efficacy. Only about 25% of patients have noted pain relief lasting one month or more.[15]

One recommended therapeutic technique involves a series of three pudendal nerve blocks using a mixture of lidocaine 1%, bupivacaine 0.25%, and a corticosteroid. This regimen allows time for the beneficial effect of the steroids to complement the early pain control from the local anesthetics. Relief from steroids usually occurs starting three to five days post-injection and lasts for three to five weeks or longer. As the steroid benefit wanes, the next nerve block injection cocktail can be performed, so the treatments are typically given at four-week intervals. Two consecutive blocks are given into the interligamentary space between the sacrospinous and sacrotuberous ligaments immediately adjacent to the ischial spine. The third block in the series is generally given by an interventional radiologist using computed tomography (CT) guidance.[55] Injections may be performed unilaterally or bilaterally as appropriate. Nerve blocks performed without sedation allow for improved communication between the patient and the treating specialist.

Patients are examined two hours after their block to determine the quality of the block, usually via pinprick sensory testing. Pain relief within minutes or a few hours from the injection confirms the diagnosis of pudendal neuropathy and the adequacy of the nerve block. The lack of any pain relief indicates that the block probably missed the pudendal nerve pathway. Image guidance is recommended to minimize technically inadequate blocks. Ultrasound guidance is suggested for repeated or sequential blocks to minimize costs and patient ionizing radiation exposure.

Transgluteal injections are sometimes preferred over a vaginal approach to ensure higher precision in placement and to decrease the possibility of infection. Some providers perform therapeutic pudendal nerve blocks using ultrasound guidance and nerve stimulator guidance. The use of MRI has also been reported.[56] 

Pudendal nerve block injections can be given monthly or as needed, but there is evidence that repeated injections may lose efficacy after two years.[57]

Sacral neuromodulation is often considered a treatment of last resort when all other treatments, including nerve decompression, have failed to provide adequate pain control. Sacral neuromodulation utilizes implanted leads and a battery pack to deliver low amplitude electrical stimulation to specific sacral nerves. This acts as a neural regulator which modifies the functional characteristics of the affected nerves to block abnormal sacral nerve reflex activity and normalize effector organ function. It has been shown to be effective in both intractable functional disorders of the rectum and lower urinary tract, as well as chronic pelvic pain. Its use in pudendal neuralgia has not been well studied, but the available data suggests that it appears safe and effective even in some otherwise intractable cases.[14] As the pudendal nerve is derived from the S 2,3 and 4 nerves, it is reasonable to expect a response from sacral neuromodulation of those same sacral ventral nerve roots.

First reported in 2014, sacral neuromodulation has been reported to be effective in some otherwise intractable cases of pudendal neuralgia, including decompression surgery failures.[14][58][59][60] However, most of these studies involve small sample sizes and single centers or institutions with limited follow-up. In one recent study of 55 pudendal neuralgia patients, 33 responded well to sacral neuromodulation therapy with a reported reduction in pain symptoms of at least 50%.[14] For purposes of neuropathic pain relief, it has been suggested that increasing the standard frequency from 14 Hz to >20 Hz would be beneficial, but this has not been confirmed.[14] Optimal parameters for neuropathic pain relief using sacral neuromodulation in pudendal neuropathy have not been determined. Sacral neuromodulation is safe, effective, minimally invasive, relatively inexpensive, and widely available. Based on the totality of the data, sacral neuromodulation is probably underutilized for pudendal neuralgia and can be considered a reasonable option for selected cases not responding to simpler measures. It should also be considered when decompressive surgery has failed and in patients with pudendal nerve entrapment who are not surgical candidates as an alternative to repeated pudendal nerve blocks.

Decompressive surgery is generally the mainstay and most definitive treatment for persistent pudendal neuralgia. As the condition is often considered a "tunnel" syndrome, decompressive surgery is a reasonable and frequently curative option for patients. A randomized control study published by Robert demonstrated the benefit of surgery over conservative care and made surgical decompression the preferred treatment for pudendal neuralgia.[61] Nerve entrapment can only be definitively identified and confirmed at the time of surgery. The overall success rate reported for decompressive surgery in properly selected patients with pudendal neuralgia is 60% to 80%.[62]

The most common site for pudendal nerve compression is in the interligamentary space between the sacrospinous and sacrotuberous ligaments. The next most common site is within Alcock's canal (also called the pudendal canal). The falciform process may compress the nerve. Congenital compression may be due to aberrant fascias, or the nerve may be squeezed between leaves or layers of the sacrotuberous ligament. Multiple anatomic variations of the pudendal nerve have been described.[31][63] The goal of decompressive surgery is the total release of the entire nerve trunk, allowing it complete mobility.[15]

Indications for decompressive surgery are severe pain/symptoms that do not respond to conservative measures, medications, and a series of good-quality image-guided pudendal nerve blocks. A positive response to an anesthetic injection of Alcock's canal is highly suggestive of a good outcome from decompressive surgery.[62][64] The lack of efficacy of a properly performed pudendal nerve block would suggest a poor surgical outcome.[15]

There are several surgical approaches for decompression of the pudendal nerve. Shafik described the first transperineal approach in 2007.[65] One minimally invasive transperineal approach uses a urologic resectoscope.[66] Robert, in France, developed the transgluteal approach that is commonly used internationally.[1] The nerve is decompressed by transecting and removing the sacrospinous ligament. It is then transposed medial and anterior to the ischial spine after opening Alcock's canal. Often, an adhesion barrier such as omentum is applied before closing. Hospitalization for 1 to 2 nights is sometimes necessary.

The most commonly used surgical approaches include transperineal, transgluteal, transischiorectal, and laparoscopic.[67] Several case series report similar results between the various approaches.[68] The use of the NIH-CPSI (chronic prostatitis symptom index) and several case series has enabled a more objective comparison between surgical approaches and demonstrated comparable results.[62] Laparoscopic decompression with an omental flap provides a better surgical field than other approaches and excellent outcomes, with 81% of patients reporting >80% reduction in pain after six months.[67] The placement of an electrode for neurostimulation at the time of laparoscopic nerve decompression for severe, intractable pudendal neuralgia has been successful but only reported in a few anecdotal cases.[69] (See our companion article on Pudendal Nerve Entrapment Syndrome.)[2]

During nerve healing after nerve decompression surgery, medications are often needed for several months to control pudendal pain and treat central sensitization. Treatment of other associated abdominal wall neuropathies should be continued. Neurectomies of iliohypogastric and ilioinguinal nerves may be necessary for complete pain control.

Decompressive surgery fails in about 30% of patients.[58] In such cases, about two-thirds of patients may still receive relief from sacral neuromodulation.[58][70]

Pulsed radiofrequency ablation has been used as an alternative to therapeutic pudendal nerve blocks and standard radiofrequency ablation.[71][72] (Pulse technology appears to improve therapeutic efficacy while minimizing heat-related complications compared to standard radiofrequency ablation.) Two recent studies totaling 90 pudendal neuralgia patients treated with pulsed radiofrequency reported significant pain relief in 89% of those treated and followed for up to 6 months.[73][74] Another study compared radiofrequency ablation with standard pudendal nerve blocks in 88 patients with pudendal neuralgia. It found rough equivalency in pain relief out to 30 days but improved symptoms with pulsed radiofrequency therapy extending from 1 to 3 months.[75] Results from different studies are difficult to evaluate or compare because of variations in equipment, treatment techniques, inclusion criteria, radiofrequency selection, duration of therapy, and methodology of reporting outcomes. While there is currently insufficient data to recommend this modality as a standard or first-line treatment for pudendal neuralgia, it can be considered as a secondary therapy. It should ideally be performed within a clinical trial.[14][15]

Lipofilling is a new therapeutic technique where perineal injections of stem cells and autologous adipose tissue into Alcock's canal are performed to relieve neuropathic pain from pudendal neuralgia. This therapy was initially evaluated in a 2015 prospective study involving 15 pudendal neuralgia patients who had failed medical treatment; 87% of the patients treated indicated an improvement in symptoms with no complications, but long-term follow-up was not reported beyond six months.[76] More extensive studies with longer-term follow-up are needed to determine if lipofilling is an effective, viable, and long-lasting treatment option for pudendal neuropathy.[15] Patients considering this treatment should ideally be enrolled in a clinical trial.

Cryotherapy appears promising based on results from similar treatments of other neuropathies, but there have not yet been sufficient studies to demonstrate efficacy or safety in treating pudendal neuralgia.[77][78][79][80] A single, small study from 2015 with only 11 patients did demonstrate an average decrease in pain of almost 60% after six months with no complications, but this has not yet been repeated in any larger, prospective trials and so cryotherapy for pudendal neuralgia must currently be considered investigational.[77]

Other treatment modalities are found on the internet and directed to desperate patients. Of the many additional interventions found in the media, many will be specious or suggest higher success than can be supported by the peer-reviewed medical literature. Physicians should be cautious in recommending or suggesting unproven therapies outside of a clinical trial. Acceptable treatments typically include conservative measures, medications, physical therapy with or without TENS, cognitive behavioral therapy, pudendal nerve blocks, sacral neuromodulation, and decompressive surgery. All other therapies (such as cryotherapy, pulsed radiofrequency ablation, and lipofilling) should be considered investigational.[15]

There is a critical lack of properly performed, large, randomized clinical trials with adequate follow-up for any treatment of pudendal neuralgia. The therapeutic recommendations listed above are based on the best available evidence, which is often very limited, and expert opinion.[15]

 Treatment Summary

  • Conservative measures such as the use of seating pads and avoidance of prolonged sitting
  • Medications such as amitriptyline, duloxetine, and gabapentin alone or in combination
  • Physical therapy, preferably with transcutaneous electrostimulation (TENS)
  • Cognitive behavioral therapy for patients with psychological effects from or contributing to their chronic pain
  • Diagnostic and therapeutic pudendal nerve blocks, preferably performed with image guidance
  • Sacral neuromodulation can be quite effective and is probably underutilized
  • Surgical decompressive surgery for appropriately selected patients (such as those who respond well to Alcock's canal injections)
  • Consider sacral neuromodulation for the 30% of patients who fail surgical decompression
  • There is currently insufficient data to recommend pulsed radiofrequency ablation, cryotherapy, or lipofilling outside of a clinical trial, but there are some promising early studies and anecdotal case reports

Differential Diagnosis

In males, the most common misdiagnosis of pudendal neuralgia is prostatitis. The National Institutes of Health attempted to clarify this issue by developing four categories of prostatitis, including "Chronic Pelvic Pain Syndrome" (CPPS), as one of the categories.[81] It is likely that at least some patients diagnosed with chronic pelvic pain syndrome actually have pudendal neuralgia. Providers should rule out inflammation in the prostate by examining prostatic secretions or seminal fluid for white blood cells. Patients originally diagnosed with prostatitis or chronic pelvic pain syndrome who fail to improve on treatment should be re-evaluated for possible pudendal neuralgia, and consideration should be given to a pudendal nerve block in such individuals.

The European Association of Urology lists 23 syndromes that present with chronic pelvic pain.[28] Each of these, including interstitial cystitis, could be considered possible pudendal neuropathy, especially if resistant to standard therapy.

Careful examination of the male genitalia will identify pathology in the vas deferens, epididymis, and testis.

In females, morphologic disease of the uterus or ovaries should be considered. For example, a diagnosis of" endometriosis" is sometimes made even without laparoscopic confirmation. Anorectal pathology can often be diagnosed by physical examination.

Several other abdominal and pelvic neuropathies that overlap with the pudendal region or can be referred to as that area should be considered.

The "Nantes" criteria have been published to guide the diagnosis of pudendal neuropathy (especially when all the criteria are met).[16]

Prognosis

The sequential treatment of pudendal neuralgia relieves or reduces symptoms in most patients. After successful pudendal nerve blocks, pain reduction usually permits a return to a normal lifestyle. Complete cures over 12 years have been reported, with some extending to 20 years. Overall success for pudendal nerve blocks is about 80%, while surgery provides extended relief in properly selected patients in 60% to 80% of those treated. Although there are occasional reports of immediate and total relief following surgery, most clinicians report pain/symptom control gradually improving over 6 to 24 months or longer. Therefore, patients should be given realistic expectations, and a post-operative treatment/monitoring program should be established.

Alternative treatments such as sacral neuromodulation, cryotherapy, pulse radiofrequency ablation, and lipofilling are promising and can reasonably be considered in intractable cases (particularly sacral neuromodulation, which is safe, minimally invasive, widely available, and generally underutilized for pudendal neuralgia) even though the medical literature is incomplete on these treatment modalities as good success rates have been reported but only in small, short term studies.

The success of the various treatment modalities may be influenced by:

  • The degree of nerve injury and duration of compression
  • The skill and experience of the individual treating physicians and their ability to work together as a multidisciplinary team
  • The availability and use of adjunctive services such as pain management, interventional radiology, psychology, physical therapy, etc.
  • Failure to recognize that the persistence of symptoms is a consistently reported part of the normal healing process even after definitive therapy
  • Central sensitization is common in patients with pudendal neuropathy and may amplify the persistence or intensity of symptoms
  • Concurrent neuropathies that may occur in pudendal neuropathy patients may require additional treatment
  • Iliohypogastric and ilioinguinal neurectomies may be necessary to fully eliminate inguinal/lower quadrant pain

The leading cause of recurrent symptoms of pudendal neuralgia is the early resumption of the activities which originally aggravated the condition, such as cycling, exercising, jogging, and prolonged sitting. For example, after the sacrospinous ligament has been surgically removed or decompressed and the “lobster claw” released, the Valsalva maneuver during lifting or squatting may force the pelvic floor to compress the nerve against the sacrotuberous ligament again and re-aggravate the injury with a return of symptoms.

Complications

Some patients will develop pains in their feet as they stand for long periods rather than sit. Medication side effects are relatively common and may require alternative drugs.

Side effects and complications from pudendal nerve blocks are rare. They include hematoma formation, pain or infection at the injection site, and neonatal anesthetic toxicity (exceedingly rare) when the nerve block is done for childbirth analgesia.[82][83][84][85]

Pudendal nerve blocks may also produce side effects indirectly from the injected steroids, such as agitation and anxiety, as well as possibly elevated blood glucose in diabetics. Placement of the needle for injection may penetrate the nerve, a rare complication causing immediate pain, sacral neuropathy, or ischial region paresthesia that may last for up to six weeks or longer.[86]

Intravascular infiltration of lidocaine and bupivacaine is rare. Initially, the patient may notice a metallic taste. A large bolus can cause significant cardiovascular problems, but this is exceedingly rare. Aspiration of the injection needle for evidence of blood is not an absolute uniform indicator of safety. Following the infiltration of medicines, transient exacerbation of pain may occur. One theory is that this is caused by cold (room temperature) injected drugs or local pressure from the volume of the injected bolus.

Surgical complications specific to pudendal decompression include injury to a small branch of the nerve. A microsurgical repair can be performed if necessary. An incomplete transaction of the sacrospinous ligament has been reported. Transection of the sacrotuberous ligament can occur, which results in the development of an unstable pelvis. (This can be avoided by using a midline vertical incision in the sacrotuberous ligament.)

Immediate, total pain relief after surgical decompression is unusual. Pain which slowly decreases over several months is common and should not be considered a surgical or procedural complication.

Deterrence and Patient Education

Prevention of pudendal neuralgia begins when the diagnosis is made. Sports medicine physicians, therapists, personal trainers, coaches, and athletes must be aware of this condition to aid in early diagnosis. For instance, cyclists often continue to cycle despite developing penile or perineal numbness. Adopting a split saddle seat can be very helpful. In the gym and during sports, training is where symptoms of neuropathy will be expressed and should be recognized. 

Pediatricians should be aware of and consider pudendal neuralgia as a possible diagnosis in patients with bladder and bowel dysfunction along with abdominal and pelvic pain, as this condition is often the result of congenital anatomic problems. In children, a pinprick test using a toothpick rather than a safety pin can be a less frightening method of conducting sensation testing.

Patient education should emphasize the role of resting the nerve, using a seating pad modified to minimize central pressure, and controlling stress. Patients may need to be reminded of the benefits of non-opioid medications and non-invasive therapies in reducing painful neuropathic signals.

Pearls and Other Issues

  • Patients with perineal discomfort or diagnosed with painful perineal pathology, such as prostatitis or chronic pelvic pain syndrome, who fail to improve on standard therapy should be re-evaluated for possible pudendal neuralgia.
  • Take advantage of physical therapy for 6 to 12 weeks despite the lack of definitive prospective studies. If it works, the patient benefits and more invasive treatments are avoided. If not, no harm is done.
  • Adding TENS treatment to physical therapy will help improve outcomes.
  • Avoid using opioid medications if possible.
  • Provide patients with realistic expectations of their prognosis and likely treatment outcomes. 
  • Take advantage of a team approach to this chronic pain problem by including physical therapists, psychologists, interventional radiologists, surgeons, and pain management specialists.
  • Consider a trial anesthetic nerve block injection into Alcock's canal to ascertain the patient's likely response to surgical decompression. If the result is insufficient or inadequate, consider using an image-guided nerve block injection.
  • Sacral neuromodulation is safe, reasonably effective, minimally invasive, and frequently underutilized for pudendal neuralgia. It should be considered a possible alternative to surgical decompression in selected patients.
  • Patients who fail decompressive surgery may still benefit from sacral neuromodulation. About 2/3 will respond.
  • Laparoscopic nerve decompression combined with simultaneous neurostimulator placement has been a successful strategy employed experimentally in a few intractable cases of severe pudendal neuralgia.
  • Consider alternative therapies (in a clinical trial if possible) such as cryotherapy, pulsed radiofrequency ablation, and lipofilling in selected patients depending on available resources and patient desires after fully and fairly reviewing all reasonable treatment options.
  • Chronic pain patients can sometimes be manipulative, frustrated, depressed, anxious, and hypercritical. Consider using mental health and pain management support to help.
  • Recognize that some patients can become suicidal and take appropriate precautions. 

Enhancing Healthcare Team Outcomes

Most healthcare professionals are generally unaware of the existence of pudendal neuralgia, nor its diagnosis and treatment. For many, chronic pelvic pain remains a morass of differing opinions, multiple tests, and various interventions. A reasonable, progressive approach incorporating local healthcare professionals in multiple specialties greatly improves patient outcomes.

End-organ specialists need to be more aware of pudendal neuralgia and consider the diagnosis in patients seen for bowel, bladder, and sexual dysfunctions as well as dyspareunia and vulvodynia. For example, pain specialists often focus on interventional spinal pain control without considering other treatment modalities available from adjunctive specialties. Patients would benefit enormously if primary care physicians, urologists, OB-GYNs, and internists developed an increased awareness and understanding of pudendal neuralgia. Neurologists also need to play a role. An integrated team, including a psychologist, physical therapist, pain specialist, interventional radiologist, OB-GYN, and urologist, in addition to the original treating primary care physician, is valuable and results in better patient outcomes. One designated member should ideally take primary control and integrate the various specialties into a coordinated multidisciplinary team.

Academic institutions and clinical centers of excellence need to show true leadership in organizing such a team approach. More formalized diagnostic techniques with uniform protocols improved monitoring, and standardization of therapeutic interventions should be developed and utilized. There is a critical need for larger, high-quality, randomized, prospective clinical trials for virtually all pudendal neuralgia treatments. Available studies currently lack sufficient numbers of patients, uniform diagnostic and outcome criteria, procedural standardization, adequate control groups, and long-term efficacy validation. Even a single, standardized symptom score to measure outcomes would greatly aid the analysis and evaluation of pre and post-treatment studies and allow better therapeutic comparisons. Pelvic pain clinical research projects should evaluate for pudendal neuralgia and specifically consider it part of their inclusion or exclusion criteria.


Article Details

Article Author

Stephen W. Leslie

Article Author

Stanley Antolak

Article Author

Michael P. Feloney

Article Editor:

Taylor L. Soon-Sutton

Updated:

9/23/2022 1:46:58 PM

PubMed Link:

Pudendal Neuralgia

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