Continuing Education Activity

Pudendal neuralgia is a chronic pelvic and perineal pain syndrome originating from damage, injury, inflammation, or irritation of the pudendal nerve. The condition is primarily a clinical diagnosis that is suggested by characteristic features, sometimes referred to as the "Nantes" criteria. Treatment is analogous to carpal tunnel syndrome, including initial conservative nerve protection measures, physical therapy, pharmacologic therapy, pudendal nerve blocks, sacral neuromodulation, and surgical decompression of the pudendal nerves. Few clinicians examine patients specifically for pudendal neuralgia or focus on common morphologic or infectious causes, resulting in delayed diagnosis and treatment. This delay often leads to negative consequences, such as inadequate pain control with subsequent patient frustration and depression. Adverse effects on cognitive, behavioral, sexual, emotional, and psychosocial health may also occur. Patients with chronic pelvic or perineal pain who are initially diagnosed with other conditions but fail to respond to standard therapy should be reevaluated for possible pudendal neuralgia, as the treatment protocol is generally completely different. This activity outlines the proper diagnostic evaluation and management of pudendal neuralgia, as well as reviewing 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.

• Identify the appropriate steps in the evaluation of pudendal neuralgia.

• Identify the management options available for pudendal neuralgia.

• Strategize how the interprofessional team enhances care coordination and communication advances multidisciplinary pudendal neuralgia treatment and improves outcomes.

Introduction

Pudendal neuralgia is the neuropathic pain component of the syndrome caused by pudendal nerve entrapment and neuropathy. 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. Injuries typically affect pelvic and perineal sensations more severely than motor or autonomic nerve functions.[1] Pudendal neuralgia is generally a bilateral process characterized by perineal pain aggravated by sitting and affects >50% of patients with pudendal nerve entrapment.[2] The condition is frequently misdiagnosed initially and is often refractory to treatment, causing intense, chronic, debilitating pain. 

Pudendal neuralgia is primarily a clinical diagnosis that is suggested by characteristic features, sometimes referred to as the "Nantes" criteria.[3][4] However, pudendal neuralgia is usually diagnosed only after many years of painful symptoms, with patients having undergone multiple evaluations, medication trials, procedures, interventions, and even surgeries. In addition to pain medicine specialists, end-organ specialists often treat patients, including gynecologists, colorectal surgeons, and urologists. The condition is significantly underdiagnosed and often inadequately or improperly treated. Consequently, a patient's quality of life is dramatically negatively impacted by resulting conditions, including depression and opioid addiction. In some cases, delays in diagnosis and proper treatment have led to confirmed patient suicides. However, when properly managed, long-term symptom control is possible, and total relief of symptoms has been reported up to 20 years after treatment.[1]

As pudendal neuropathy is often a tunnel entrapment syndrome, treatment is analogous to carpal tunnel syndrome, including initial conservative nerve protection measures, physical therapy, pharmacologic therapy, pudendal nerve blocks, sacral neuromodulation, and surgical decompression of the pudendal nerves.[3][4] However, pudendal neuralgia and nerve entrapment are largely unknown and unstudied conditions. Therefore, there is a general lack of quality research or studies demonstrating the optimal treatment strategy. The information presented here is based on the best peer-reviewed medical literature and consensus expert opinions.

Etiology

Pudendal Nerve Entrapment Sites

The pudendal nerve is generally composed of fibers from the ventral nerve roots of S2, S3, and S4.[5] 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.[1][6] The net effect is analogous to a "clamp" or "lobster claw," which can pinch or impinge on the nerve.[6] Upon leaving this site, the nerve travels through the pudendal canal (ie, Alcock's canal), dividing into the deep and superficial perineal nerves, the dorsal nerve of the penis or clitoris, and the inferior rectal nerve. However, many nerve structure variations have been noted during surgery and anatomical dissections. Pudendal nerve entrapment is commonly subdivided into 4 types based on the location of the compression. (For additional information, see also "Pudendal Nerve Entrapment Syndrome"). The 4 types are comprised of the following sites of entrapment:[1]

• Type I: below the piriformis muscle as the pudendal nerve exits the greater sciatic notch
• Type II: between the sacrospinous and sacrotuberous ligaments; the most common site of pudendal nerve entrapment
• Type III: within Alcock's canal
• Type IV: terminal nerve branches only (ie, inferior rectal nerves, superficial and deep perineal nerves, and the dorsal nerve of the penis or clitoris)

Pudendal Neuralgia Etiolgies

Pudendal neuralgia (PN) is generally a "tunnel" syndrome, typically resulting from cumulative, repetitive microtrauma to the nerve. Furthermore, bony remodeling in the pelvis commonly occurs secondary to repetitive overuse of pelvic floor muscles, resulting in changes to the ischial spine and the inferior lateral angle of the sacrum. When untreated and nerve damage advances, pudendal neuropathy can progress from minor localized symptoms, most commonly the bladder, to more painful generalized symptoms. Severe pain may occur in several areas and is often confused with various structural and organ diseases. Frequently, the pain becomes chronic and disabling in intensity. Indirect trauma, including viral infections (eg, HIV and herpes zoster), multiple sclerosis, and diabetes, can also cause PN. Stress is not an underlying etiology but may be a potent aggravator of neuropathic pain. Herpes simplex infections, benign tumors, and metastatic lesions to the nerve pathway are infrequent causes of PN; however, common causes include:[7]

• Childbirth injuries due to stretching of the pelvic musculature from the fetal head [8][9] 
• Chronic constipation [1]
• Direct trauma, including falls, motor vehicle accidents, and pelvic surgeries (eg, pelvic organ prolapse repairs with mesh) [10][11][12]
• Prolonged sitting (eg, sewists, computer operators, office workers, judges, concert pianists, commercial drivers, chess players, and locomotive engineers) [2][1]
• Radiation therapy (eg, for prostate, rectal, and gynecological cancers) [1]
• Repetitive hip flexion (eg, sports activities, exercising, jogging, cycling) [7][13]

Epidemiology

Pudendal neuralgia (PN) is often unrecognized; therefore, the actual incidence is unknown.[14] However, the International Pudendal Neuropathy Association estimates an incidence of 1 in 100,000 within the general population.[14] A study by Spinosa et al reported a 1% incidence in the general population. Though PN occurs in both genders, women are affected more than men. Children can also be affected due to congenital anomalies in the nerve pathway.[15] Orphanet, a European health information database, states pudendal neuralgia affects 4% of all patients undergoing consultations for pain control, occurring in 7 women for every 3 men.[16] Many clinicians, especially those who routinely treat pudendal neuralgia, believe the true incidence is significantly higher than reported in the existing literature.[14]

Pathophysiology

Compression of the pudendal nerves, which may be severe, is the most common pathophysiologic cause of PN., which is typically visible to the surgeon during decompression and transposition surgeries. 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, direct trauma following repetitive or serious falls (eg, skiers, skaters, snowboarders, and other athletes), or excessive sitting (eg, cyclists). A hypertrophied obturator internus muscle can also compress the nerve in the pudendal canal. Stretching of the pudendal nerves is occasionally observed as well.[17] 

History and Physical

Clinical Symptoms

PN should be suspected in all patients with a history of pelvic pain, especially in the perineal and genital areas, with or without concurrent sexual, bladder, or bowel dysfunction. Generally, pain onset is usually subtle, except when caused by acute trauma, being less severe in the morning and progressing throughout the day. Patients frequently characterize the pain as burning, tingling, aching, stabbing, and electric shock-like.[3] In over half of patients, pain symptoms are exacerbated when sitting and relieved when standing, lying down, or seated on a toilet.[7] Additionally, referred sciatic pain, medial thigh pain indicating obturator nerve involvement, pain after ejaculation, worsening discomfort after intercourse, and erectile dysfunction may be present. Occasionally, patients may also have vague, neuropathic pain in areas outside pudendal nerve innervation, including the lower abdomen, posterior and inner thigh, or lower back.[4] However, 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 secondary to PN.[4]

Patients with PN frequently complain of chronic perineal pain, although they may also present with bowel, bladder, and sexual dysfunction with or without discomfort. The pain distribution of PN may either be limited to the perineum or extend to the vulva, vagina, clitoris, perineum, and rectum in females and the glans penis, scrotum, perineum, and rectum in males.[2] Furthermore, coccygeal pain and pain referred to the calf, foot, and toes are common PN presentations. Some types of perineal pain indicate central sensitization, including allodynia (ie, pain or discomfort with clothing contact) or a foreign body sensation in the vagina or rectum, often described as sitting on a golf ball or a hot poker in the rectum.[3] 

Additional symptoms associated with PN include urinary frequency, dysuria, urgency, symptoms mimicking interstitial cystitis, painful ejaculation, dyspareunia, painful nocturnal orgasms, and persistent sexual arousal. Clinicians should also inquire about activities involving repetitive hip flexion, prolonged sitting, falls, and alleviating or aggravating factors suggestive of PN.[18]

Physical Examination 

A visual examination will exclude apparent lesions in the vulva, perineum, male genitalia, or rectum. The rectal sphincter should be evaluated, and any tender regions of the anal canal (eg, anal fissures) should be inspected. In male patients, the testis, epididymis, vas deferens, and prostate should be examined for tenderness and masses; the prostate examination should also include an evaluation of the expressed prostate secretions (EPS) or a post-massage urinalysis for inflammatory cells. In females, the pelvic floor and the obturator internus muscles should be softly palpated to evaluate for muscle spasms and tenderness. A bimanual examination should be performed with gentle palpation of the uterus and ovaries; pressure should be placed over the T12 abdominal cutaneous and the iliohypogastric nerves, which may be misinterpreted as organ pain.[19] 

Clinicians should evaluate men and women to assess each pudendal nerve branch for pinprick sensation, including the glans penis or clitoris, posterior scrotum or labia, and posterior anal skin bilaterally. In patients with PN, ≥1 of the 6 branches may show hyperalgesia, hypoalgesia, or analgesia using the thigh as the control.[20] Palpation of the medial pudendal nerve pathway to the ischial spine and over Alcock's canal is essential as reproducing pain with palpation of these sites is considered diagnostic of a mid-nerve pudendal injury. This finding, called the "Valleix phenomenon," is analogous to the Tinel sign in carpal tunnel syndrome.[21] 

Additionally, patients with PN are commonly found to have other peripheral mononeuropathies, including abdominal cutaneous neuropathies, ilioinguinal and iliohypogastric neuropathies, thoracolumbar junction syndrome (ie, 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 (PN) is primarily a clinical diagnosis that is suggested by characteristic features, sometimes referred to as the "Nantes" criteria, which include:[3][4]

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

There currently are no studies to diagnose PN definitively; however, neurophysiological studies are commonly recommended for diagnostic evaluation and treatment monitoring. Additionally, abdominal, lumbosacral spine, and pelvic magnetic resonance imaging (MRI) and computed tomography (CT) are typically utilized to exclude differential diagnoses and for image-guided nerve blocks.[22][3]

Neurophysiological Studies

In addition to evaluating PN, stimuli from the neurophysiologic testing often reproduce indicators of central sensitization (eg, pain in a toe from a stimulus to the labium or contralateral inguinal pain during pudendal nerve terminal motor latency testing). Neurophysiological studies include:

• Quantitative warm thermal threshold sensitivity testing: Compressed nerves lose the ability to transmit thermal and vibratory sensory changes quickly; therefore, this neurophysiological test is the easiest and most commonly performed study for possible PN.[23][24] 
• Warm sensory threshold detection testing: A probe is placed 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 (eg, NTE–2 and TSA 2 thermosensory testers and the MSA thermal stimulator) are commercially available, noninvasive, and easily used in an outpatient clinic.[25] 
• Biothesiometry: A probe with variable vibratory intensity is used to identify vibratory sensory thresholds, though warm sensory threshold detection is easier and more commonly performed. 
• Pudendal nerve terminal motor latency testing (PNTML): The test measures motor function in the inferior rectal nerve and is used for diagnosis and monitoring treatment results.[26] PNTML can be performed in an outpatient setting 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.[26]
• Intraoperative neurophysiologic testing: This type of evaluation 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: This study is not considered specific enough to be a recommended part of the routine diagnostic evaluation.[3]
• Somatosensory evoked potential (SSEP) testing: Pudendal neuropathy is often confirmed with this study. 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.[27][28]

Pudendal Nerve Block Confirmation

Many experts have recommended pudendal nerve block injections as a diagnostic tool, though high-quality studies to validate this technique are lacking.[3][29] Injection of a short-acting local anesthetic under image guidance (CT, ultrasound, or fluoroscopy) into the sacrospinous ligament, approximately 1 cm inferior and medial to the ischial attachment where the pudendal nerve enters the lesser sciatic foramen, is the most commonly used procedure.[30] Frequently, the precise location of the block is guided by patient statements or pudendal symptoms as the needle is inserted. Injections may also be given directly into Alcock's canal, which can be identified using imaging with contrast. However, these are generally considered most useful to indicate if the patient is a potential candidate for surgical decompression.[3] While primarily a transperineal procedure in men, a pudendal nerve block can also be performed transvaginally in women. Perirectal and transgluteal approaches have also been described.[31][32]

At the time of the diagnostic injection, clinicians should ensure that the patient is actively experiencing significant pain, quantified and recorded immediately before, during, and for two hours after the injection. However, patients with organ symptoms but without pain would be excluded from having their diagnosis made by this modality. A skin pin-prick test may ascertain skin sensitivity before the procedure. 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. A pudendal nerve block with an immediate reduction in pain of ≥50% is considered a confirmatory result. Additionally, a successful 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.[33][3][30][34]

Image guidance, usually with CT or ultrasound, is commonly used to increase the diagnostic reliability of a pudendal nerve block.[3][30][34] However, due to physician inexperience or lack of training, up to 20% of diagnostic pudendal nerve blocks may be of poor technical quality and fail to provide substantial pain relief, even in otherwise confirmed cases. Therefore, potentially, only 80% of patients are correctly diagnosed with pudendal neuropathy using this method.[35][36] 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.[30] (For additional information, see "Pudendal Nerve Blocks")[30]

Treatment / Management

As pudendal neuropathy is often a tunnel entrapment syndrome, treatment is analogous to carpal tunnel syndrome, including:

• Conservative nerve protection measures initially, along with physical therapy and medications
• Pudendal nerve block perineural injections given monthly as needed or as a series of 3 injections every 4 weeks
• Consideration of sacral neuromodulation and surgical decompression of the pudendal nerves if unresponsive to conservative treatments

Desperate patients may find additional treatment modalities; however, these interventions found in the media are often specious or suggest success rates unsupported 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 supportive measures, medications, physical therapy with or without TENS, cognitive behavioral therapy, pudendal nerve blocks, sacral neuromodulation, and decompressive surgery. All other therapies (eg, cryotherapy, pulsed radiofrequency ablation, and lipofilling) should be considered investigational.[3] There is a critical lack of adequately performed, large, randomized clinical trials with adequate follow-up for any treatment of PN; therefore, these therapeutic recommendations are limited based on the best available evidence and expert opinion.[3]

Supportive Therapy

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" can be constructed or purchased commercially. With the center section of the seating pad removed, the perineum has no pressure, and the patient primarily sits on their ischial tuberosities. In some cases, these pads may even be curative. Lifestyle modifications, including the avoidance of sitting, use of a standing workstation, and cessation of hip flexion exercises (eg, cycling, jogging, and rowing), are essential to prevent repeated pudendal nerve injury. Approximately 20% to 30% of patients report improvement with supportive therapy alone.

Furthermore, clinicians should consider supportive therapy for mental health in some patients. Individuals with PN are typically only diagnosed after being symptomatic for several years, seeing various physicians, and undergoing extensive, repetitive testing. Often, patients have had multiple surgeries and are told their condition is psychosomatic. Anxiety, depression, and resistance to new treatments are common in patients with PN. Moreover, patients may become angry, frustrated, or feel threatened if their standard therapy (eg, opioids) is questioned or modified.[37] Therefore, referral to an experienced psychologist should be considered as treatment progresses, as at any time during treatment and even after long-term resolution, stress may precipitate or aggravate the pain.

Pharmacologic Therapy

Polypharmacy is often necessary to control the multiple symptoms of neuropathic pain and common central sensitization in patients with PN patients.[3] Control of ectopic firing from the injured nerve and the dorsal ganglion can be achieved with various drugs, including antibiotics, tricyclic amines, and central-acting sympatholytic medications. Close monitoring for treatment response and adverse effects is essential, with medication adjustments as indicated.

Because there is a paucity of prospective, randomized studies to indicate which medications are most effective for PN treatment, most pharmacologic therapy is based on general neuropathic pain studies. A combination of medications is often necessary to control symptoms.[3] Medication selection should consider the patient's medical history, previous medications, adverse effects, comorbidities, drug effectiveness, possible interactions, and potential risk of addiction. Opioids should be avoided if possible. Initial treatment regimens include amitriptyline, a selective serotonin-norepinephrine reuptake inhibitor (eg, duloxetine), or an antiepileptic (eg, gabapentin and pregabalin). Antihistamines may have a beneficial adjuvant effect.[3][38][39] Medications commonly used for PN treatment include:[3] 

• Amitriptyline 10 mg every evening initially, increasing the dosage every 5 days to a maximum of 50 mg daily as tolerated.
• Clonidine 0.1 mg every evening for sympathetically moderated pain. Patients often find this is also a very useful sedative for sleep.
• Compounded topical creams containing gabapentin, ketamine, and clonidine may be useful.
• Duloxetine 30 mg daily for 1 week initially; then, increase the dosage to 60 mg daily. No additional benefit is noted from increasing the dose any further, however.
• Gabapentin 300 mg TID initially, then titrated up to 900 mg 3 times a day or pregabalin 75 mg twice daily, which may be increased to a maximum of 300 mg twice daily. Gabapentin and pregabalin are both gamma-aminobutyric acid analogs, but pregabalin is more potent, has greater bioavailability, is more quickly absorbed, and has fewer adverse effects.[40]
• Ketamine oral troches and nasal spray may be necessary when pain is unrelenting.

Cognitive Behavioral Therapy 

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.[41][42] Generally, cognitive behavioral therapy is recommended as a complementary or adjunctive therapy in patients with PN who also demonstrate any psychological effects associated with chronic pain, including 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.[3][43] A 2016 review of 1024 chronic pain patients found that about 34% had severe depression and almost 61% had probable depression.[44] Additionally, chronic pain tends to increase total healthcare costs for those individuals substantially.[44][45]

Physical Therapy 

For patients with tender, spastic pelvic floor musculature, physical therapy may be a useful adjunct therapy. Physical therapy is most helpful for levator ani syndrome or similar myofascial syndromes involving the lateral rotator group (ie, obturator internus and piriformis muscles) for at least 6 to 12 weeks.[3] Muscle-relaxing treatments are generally preferred. While most experts recommend physical therapy, there is a lack of adequately performed studies to validate its efficacy definitively.[46][47][48][49]

Transcutaneous Electrical Nerve Stimulation (TENS) 

Transcutaneous electrical nerve stimulation (TENS) has been used with reasonable success for pelvic pain syndrome, perineal discomfort, and prostatodynia. However, there is minimal data on its use specifically for pudendal neuralgia.[3] Experience with TENS for various pelvic and perineal pain syndromes strongly suggests it can be helpful for pudendal neuralgia.[50][51][52] Adding TENS treatment to standard physical therapy has shown a benefit in reported symptomatic relief compared to physical therapy alone.[53] However, there is no standardization on TENS therapy for pelvic pain or pudendal neuralgia, with various techniques, protocols, treatment durations, electrical frequencies, and electrode types, sizes, and locations being reported.[3] In a 2017 study by Sharma et al. of 120 chronic pelvic and perineal pain patients with no identifiable underlying cause, every patient treated with TENS showed improvement, with the greatest benefit in those receiving the highest tested frequency of 75 Hz to 100 Hz.[51] 

Several patterns of TENS electrode placements have been recommended, including along the tibial or sacral S2 to S4 nerve roots, as well as direct perineal stimulation with circular penile or vulvar electrodes.[3] Since the noninvasive treatment is safe, widely available, relatively inexpensive, and appears reasonably effective, clinicians may consider easily incorporating TENS therapy into existing physical therapy protocols and other conservative treatments. Still, there is insufficient data to make it a first-line therapy.[3]

Pudendal Nerve Block 

Pudendal nerve blocks are frequently utilized to support a PN diagnosis, but their therapeutic role is less clear. Due to a lack of high-quality prospective, randomized studies demonstrating efficacy, there is no consensus on the optimal medications, preferred protocols, or the long-term value of repeated injections.[3] Short-acting local anesthetics are used for diagnostic pudendal nerve block testing, but no definitive, recommended agent exists for long-acting therapeutic injections. Both local anesthetics and corticosteroids have been used separately and in combination with roughly similar results. Utilizing a mixture of short and long-acting local anesthetics and steroids may have the advantage of immediate and sustained relief, though approximately 25% of patients have noted pain relief lasting one month or more.[3] Pudendal nerve block injections can be given monthly or as needed, but there is evidence that repeated injections may lose efficacy after two years.[54]

One recommended therapeutic technique involves a series of 3 pudendal nerve blocks comprised of lidocaine 1%, bupivacaine 0.25%, and a corticosteroid injected unilaterally or bilaterally. This regimen allows time for the beneficial effect of the steroids to complement the early pain control from the local anesthetics. Symptomatic relief from steroids usually occurs within 3 to 5 days and lasts an average of 3 to 5 weeks. The injection of combined agents is repeated every 4 weeks so that as the steroid benefit wanes, another dose is given. Two consecutive blocks are delivered into the space between the sacrospinous and sacrotuberous ligaments immediately adjacent to the ischial spine. Transgluteal injections are sometimes preferred over a vaginal approach to ensure increased precision and decrease the possibility of infection.[55] The third block in the series is typically administered by an interventional radiologist using CT guidance.[56] Because patients are examined after 2 hours to determine the quality of the block, usually via pinprick sensory testing, nerve blocks performed without sedation allow for better communication between the patient and the treating specialist. Pain relief within a few hours from the injection confirms the diagnosis of pudendal neuropathy and the adequacy of the nerve block. Conversely, continued pain indicates that the block likely missed the pudendal nerve pathway. Image guidance (eg, CT, MRI, and ultrasound) is recommended to reduce technically inadequate blocks; ultrasound guidance is preferred for repeated or sequential blocks to minimize costs and patient ionizing radiation exposure.

Sacral Neuromodulation Therapy

Sacral neuromodulation is often considered a treatment of last resort when 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 that modifies the affected nerves' functional characteristics to block abnormal sacral nerve reflex activity and normalize effector organ function. Sacral neuromodulation has been shown to effectively treat intractable functional disorders of the rectum and lower urinary tract, as well as chronic pelvic pain. Treatment of PN has not been well studied, but some evidence suggests that sacral neuromodulation is safe and effective even in some intractable cases. The pudendal nerve is derived from the S2, S3, and S4 nerves; therefore, therapeutic response from sacral neuromodulation of those same sacral ventral nerve roots is reasonable.[16]

First reported in 2014, sacral neuromodulation has been reported to be effective in some otherwise intractable cases of PN, including decompression surgery failures.[16][57][58][59] However, most of these studies involve small sample sizes and single centers or institutions with limited follow-up. In one recent study of 55 patients with PN, 33 reported a 50% reduction in pain with sacral neuromodulation therapy.[16] For neuropathic pain relief, increasing the standard frequency from 14 Hz to at least 20 Hz has been proposed as more beneficial but has not been confirmed.[16] Optimal parameters for neuropathic pain relief using sacral neuromodulation in pudendal neuropathy have not been determined. Sacral neuromodulation may be a reasonable alternative for selected cases not responding to simpler measures as this modality is considered safe, effective, minimally invasive, relatively inexpensive, and widely available. However, this modality is currently underutilized for PN treatment. Sacral neuromodulation may also be considered when decompressive surgery has failed and as an alternative to repeated pudendal nerve blocks in patients with pudendal nerve entrapment who are not surgical candidates.[16][57][58][59]

Decompressive Surgery

Decompressive surgery is the most definitive treatment for persistent PN. The condition is often considered a "tunnel" syndrome, so decompressive surgery is frequently a curative option for patients. Furthermore, nerve entrapment is only definitively confirmed at the time of surgery. One randomized control study demonstrated the benefit of surgery over conservative care, recommending surgical decompression as the preferred treatment for PN.[60]  The overall success rate reported for decompressive surgery in appropriately selected patients with PN is 60% to 80%.[61]

The most common site for pudendal nerve compression is in the interligamentary space between the sacrospinous and sacrotuberous ligaments. The second most common site is within Alcock's canal (ie, the pudendal canal). The falciform process may also compress the nerve. Congenital compression may be due to aberrant fascias, or the nerve may be squeezed between layers of the sacrotuberous ligament. Multiple anatomic variations of the pudendal nerve have been described.[32][62] Subsequently, the goal of decompressive surgery is the total release of the entire nerve trunk to allow complete mobility.[3]

Indications for decompressive surgery are severe pain or symptoms unresponsive to other therapies, including conservative measures, medications, and image-guided pudendal nerve blocks. A positive response to an anesthetic injection of the pudendal canal is highly suggestive of a good outcome from decompressive surgery.[61][63] However, persistent symptoms following a properly performed pudendal nerve block indicate that surgical decompression is unlikely to be successful.[3]

The most commonly used surgical approaches include transperineal, transgluteal, transischiorectal, and laparoscopic.[64] Several case series have reported similar results between the various approaches.[65] The chronic prostatitis symptom index (NIH-CPSI) has enabled a more objective comparison between surgical approaches and demonstrated comparable results.[61] Typically, decompression is achieved by transecting and removing the sacrospinous ligament, after which the pudendal nerve is transposed medial and anterior to the ischial spinel. Often, an adhesion barrier such as omentum is applied before closing the incision. Hospitalization for 1 to 2 nights is occasionally necessary. A transperineal approach using a urologic resectoscope and a transgluteal approach commonly used internationally have been reported; however, laparoscopic decompression with an omental flap has been shown to provide a better surgical field than other approaches and excellent outcomes, with 81% of patients reporting >80% reduction in pain after 6 months.[64][66][67][2] Additionally, 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.[68] (For additional information on decompressive surgery, see "Pudendal Nerve Entrapment Syndrome")[1]

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 also should be continued. Neurectomies of iliohypogastric and ilioinguinal nerves may be necessary for complete pain control. However, in about 30% of patients, decompressive surgery fails.[57] About two-thirds of patients may still receive relief from sacral neuromodulation in such cases.[57][69]

Pulsed Radiofrequency Ablation

Pulsed radiofrequency ablation has been used as an alternative to therapeutic pudendal nerve blocks and standard radiofrequency ablation.[70][71] Pulse technology improves therapeutic efficacy while minimizing heat-related complications compared to standard radiofrequency ablation. In 2 recent studies with 90 patients treated with pulsed radiofrequency and followed for up to 6 months, 89% reported significant pain relief.[72][73] Another study compared radiofrequency ablation with standard pudendal nerve blocks in 88 patients with PN and found pain relief to be relatively equivalent in the first 30 days; however, with pulsed radiofrequency therapy, symptoms were more improved from 1 to 3 months.[74] Due to differences such as methodology and inclusion criteria, results from various studies are difficult to compare. While there is insufficient data to recommend this modality as a standard or first-line treatment for pudendal neuralgia, pulsed radiofrequency ablation may be considered a secondary therapy ideally performed within a clinical trial.[16][3]

Lipofilling 

Lipofilling is a new therapy using a technique similar to a transperineal pudendal nerve block, where stem cells and autologous adipose tissue are injected into Alcock's canal to relieve neuropathic pain from PN. This therapy was initially evaluated in a 2015 prospective study involving 15 patients with PN who had failed medical treatment; 87% of treated patients indicated an improvement in symptoms with no complications, but long-term follow-up was not reported beyond 6 months.[75] More extensive studies with extended follow-up periods are needed to determine if lipofilling is an effective, viable, and long-lasting treatment option for PN.[3] Patients considering this treatment should ideally be enrolled in a clinical trial.

Cryotherapy

Cryotherapy appears promising based on studies of similar neuropathies, but sufficient evidence of the efficacy or safety of treating PN with this modality is lacking.[76][77][78][79] A single, small study from 2015 with only 11 patients demonstrated a 60% pain reduction on average after 6 months with no complications. However, this has not yet been repeated in larger, prospective trials, so cryotherapy must be considered an investigational treatment for PN.[76]

Monitoring Therapeutic Response

The monitoring of therapeutic response can be more objective when using symptom scores. Clinical experience has shown that the National Institutes of Health - Chronic Prostatitis Symptom Index (NIH-CPSI) is a helpful metric for both genders with simple changes in anatomical terms.[80] Additionally, the American Urological Association Symptom Score Index (AUASI), also known as the International Prostate Symptom Score (IPSS), is beneficial for monitoring patients experiencing urinary symptoms. This symptom score index has been validated in both genders and is widely available in multiple languages.[81]

Treatment Summary

• Supportive therapy (eg, use of seating pads and avoidance of prolonged sitting)
• Medications (eg, amitriptyline, duloxetine, and gabapentin)
• Physical therapy, preferably with transcutaneous electrostimulation (TENS)
• Cognitive behavioral therapy for patients with psychological effects from or contributing to chronic pain
• Diagnostic and therapeutic pudendal nerve blocks, preferably with image guidance
• Sacral neuromodulation, often underutilized
• Surgical decompressive surgery for appropriately selected patients (eg, those who respond well to Alcock's canal injections)
• Sacral neuromodulation, considered in patients who fail surgical decompression
• Not recommended due to insufficient data: pulsed radiofrequency ablation, cryotherapy, or lipofilling outside of a clinical trial

Differential Diagnosis

In males, the most common misdiagnosis of PN. The National Institutes of Health attempted to clarify this issue by developing 4 prostatitis categories, including chronic pelvic pain syndrome (CPPS).[82] Therefore, patients with PN misdiagnosed with CPPS are also likely. Clinicians should rule out inflammation in the prostate by examining prostatic secretions or seminal fluid for white blood cells. Patients initially diagnosed with prostatitis or CPPS and who fail to improve with treatment should be re-evaluated for possible PN. 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.[29] Differential diagnoses, including interstitial cystitis and pathology in the vas deferens, epididymis, and testis, should be considered, especially if resistant to standard therapy. Careful examination of the male genitalia will identify pathology in the vas deferens, epididymis, and testis.[29]

In females, differential diagnoses include interstitial cystitis and morphologic disease of the uterus or ovaries (eg, endometriosis, vestibulitis, and anorectal pathologies). Other abdominal and pelvic neuropathies that overlap or refer to the pudendal region should also be considered.[4]

Furthermore, pediatricians should be aware of and consider PN 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.

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 appropriately selected patients in 60% to 80% of those treated. Although there are occasional reports of immediate and total relief following surgery, most clinicians report symptom control gradually improving over 6 to 24 months or longer. Therefore, patients should be given realistic expectations, and a postoperative treatment and monitoring program should be established.

Alternative treatments, including sacral neuromodulation, cryotherapy, pulse radiofrequency ablation, and lipofilling, should be considered in intractable cases, particularly sacral neuromodulation, which is safe, minimally invasive, widely available, and generally underutilized for PN. Though the medical literature is incomplete on these treatment modalities, reasonable success rates have been reported 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 present.
• The skill and experience of the individual treating physicians and their ability to work together as a multidisciplinary team.
• The availability of therapeutic modalities and clinician use of adjunctive services (eg, pain management, interventional radiology, psychology, and physical therapy) to manage PN.
• 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 PN and may amplify the persistence or intensity of symptoms.
• Familiarity with concurrent neuropathies that may occur in pudendal neuropathy patients and may require additional treatment.
• Recognition that iliohypogastric and ilioinguinal neurectomies may be necessary to eliminate inguinal or lower quadrant pain.

The leading cause of recurrent symptoms of PN is the early resumption of the activities that initially 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 reaggravate the injury with a return of symptoms.

Complications

Complications associated with PN are primarily secondary to the various treatments used. Even with supportive therapies such as standing for long periods rather than sitting, some patients will develop foot pains. Adverse effects of pharmacologic therapy are relatively common and may require alternative medications. Complications due to pudendal nerve blocks are rare, including hematoma, infection, and injection site pain. Neonatal anesthetic toxicity has been very rarely reported when performed for childbirth analgesia.[83][84][85][86] Pudendal nerve blocks may also produce adverse 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 >6 weeks.[87]

Intravascular infiltration of lidocaine and bupivacaine is also a rare complication, indicated by a metallic taste in the patient's mouth after administration. A large bolus can cause significant cardiovascular problems, which is exceedingly rare. Aspiration of the injection needle for evidence of blood is not an absolute preventive safety technique. If infiltration of a medication does occur, transient exacerbation of pain is common, theoretically caused by the intravascular injection of a relatively colder agent 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, transection of the sacrotuberous ligament, and an incomplete transaction of the sacrospinous ligament has been reported. Immediate, total pain relief after surgical decompression is unusual. More commonly, pain slowly decreases over several months and should not be considered a surgical or procedural complication.

Deterrence and Patient Education

Prevention of PN 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. 

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 nonopioid medications and noninvasive 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 successful, the patient benefits and more invasive treatments are avoided. However, no harm is done if there is no improvement.
• 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, which should be considered a possible alternative to surgical decompression in selected patients.
• Two-thirds of patients who fail decompressive surgery will still respond to sacral neuromodulation.
• 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 (eg, 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 referrals.
• 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 or 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 numerous specialties dramatically 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, gynecologists, neurologists, and internists developed an increased awareness and understanding of pudendal neuralgia. An integrated team, including psychology, physical therapist, pain specialist, interventional radiology, gynecology, and urology clinicians, in addition to the original treating primary care clinician, 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 must show 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. A critical need exists for more extensive, high-quality, randomized, prospective clinical trials for virtually all pudendal neuralgia treatments. Available studies lack sufficient 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 assist in the analysis and evaluation of pretreatment and treatment response studies, allowing better therapeutic comparisons. Pelvic pain clinical research projects should evaluate patients for pudendal neuralgia and specifically consider it part of their inclusion or exclusion criteria.