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Pudendal Neuralgia


Pudendal Neuralgia

Article Author:
Taylor Soon-Sutton
Article Author:
Michael Feloney
Article Editor:
Stanley Antolak
Updated:
9/3/2020 10:40:04 AM
For CME on this topic:
Pudendal Neuralgia CME
PubMed Link:
Pudendal Neuralgia

Introduction

Pudendal neuralgia (PN) is the pain component of the pudendal syndrome that is caused by pudendal neuropathy. Pudendal neuropathy affects both genders and occurs in children due to congenital anomalies in the nerve pathway. It is commonly a bilateral process. Characteristic perineal pain that is aggravated by sitting is present in over 50% of patients.[1] The pudendal nerve is a mixed nerve having sensory, motor, and autonomic functions. As a result, inflammation or injury to the nerve can also result in the bladder, bowel, sexual and autonomic dysfunctions. The pudendal nerve is generally composed of fibers from the nerve roots of S2, 3, and 4.[2] 

The nerve travels anterior to the piriformis muscle then passes between the sacrotuberous and sacrospinous ligaments, which are analogous to a "clamp" or "lobster claw," "pinching" or impinging on the nerve.[3] Upon leaving this site, the nerve travels through the pudendal canal (Alcock canal) and divides into the perineal nerve, the dorsal nerve of the penis or clitoris, and the inferior rectal nerve. Many variations in the nerve structure have been noted during surgery or anatomical dissections. Bony remodeling in the pelvis occurs commonly and is related to repetitive use of pelvic floor muscles, which results in 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, and progresses gradually as nerve damage continues. Severe pain may occur in many sites and may be confused with morphologic/organ disease.

Symptoms are often treated by end-organ specialists, including gynecologists, colorectal surgeons, and urologists. The diagnosis is usually made after many years of symptoms, during which time the patients have undergone multiple evaluations, trials of medications, and surgeries. Tragically, this often leads to opioid addiction, and patient suicides have been confirmed. When treated, long term symptom control is possible and total relief of symptoms has been reported up to 20 years after treatments.

Etiology

Pudendal neuralgia (PN) is a tunnel syndrome, typically resulting from cumulative, repetitive microtrauma to the nerve. 

Common causes include:

  • Prolonged sitting (e.g., seamstress, computer operators, judges, concert pianists, locomotive engineers)
  • Repetitive hip flexion (sports activities, exercising, jogging, cycling)
  • Direct trauma including falls, motor vehicle accidents, and pelvic surgeries, especially when using mesh
  • Radiation therapy especially in males treated for prostate cancer and patients treated for rectal and gynecological cancers  

Infrequent causes include:

  • Metastatic lesions to the nerve pathway and herpes simplex infection

Stress is not causal, but maybe a potent aggravator of neuropathic pain.

Epidemiology

Pudendal neuralgia (PN) is often unrecognized, so the true incidence is unknown.[4] Estimates from The International Pudendal Neuropathy Association are 1 in 100,000 of the general population. Spinosa et al. document the incidence at 1% in the general population, affecting women more than men.[5] 

Orphanet states PN affects 4% of patients undergoing consultation for pain and affects seven women for every three men. Many providers, especially those that treat PN, believe the actual incidence rates are significantly higher than stated in the existing literature.[4]

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 compression is frequent and noted when aberrant fascias are found and when the nerve travels through the sacrotuberous ligament. Acquired compressions include scarring after pelvic surgeries and suspected hematomas after repetitive serious falls, as in snow-boarders.

A hypertrophied obturator internus muscle may compress the nerve in the pudendal canal. A dense, enlarged falciform process is seen in some athletes. Stretch of the nerves is occasionally observed. A review of laboratory studies of mid-nerve injuries will provide insight into the neurochemical effects of nerve compression.

History and Physical

Pudendal neuralgia (PN) should be suspected in 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 pain and may also experience tingling, aching, stabbing, and shock-like pain. In over 50% of patients, pain is exacerbated while sitting and relieved when standing, lying down, or seated on a toilet.[6] 

Patients with PN may present with bowel, bladder, and sexual issues without pain. Pain distribution may be limited or extensive and may include the vulva, vagina, clitoris, perineum, and rectum in females; 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 - allodynia. This is an indicator of central sensitization. A pelvic foreign body sensation such as sitting on a golf ball or a hot poker in the rectum also 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.[7] 

Other symptoms associated with PN include urinary frequency, urgency, symptoms mimicking interstitial cystitis, painful ejaculation, dyspareunia, painful nocturnal orgasms, and persistent sexual arousal.[8] Patients should be asked about activities involving repetitive hip flexion, prolonged sitting, falls, and alleviating/aggravating factors that may suggest the diagnosis of PN.

Physical Exam

It is essential in both genders to test each pudendal nerve branch for pinprick sensation, glans (clitoris), posterior scrotum (labia), and posterior anal skin, bilaterally.[9] Using the thigh as the control, one or more of the six branches may show hyperalgesia, hypalgesia, or analgesia. 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 spasm and tenderness. The prostate examination should include evaluation of the expressed prostate secretions (EPS) or a post-massage urinalysis (PPM) for inflammatory cells.[10] 

It is most important to palpate the pathway of the pudendal nerve medial to the ischial spine and over the Alcock canal. When palpation of these sites reproduces pain in the pudendal distribution, it indicates a "mid-nerve" injury, the Valleix phenomenon. It is a diagnostic of mid-nerve injury and is analogous to the Tinel sign in carpal tunnel syndrome.[11] 

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 PN patients. These include abdominal cutaneous neuropathies, ilioinguinal and iliohypogastric neuropathies, the thoracolumbar junction syndrome or Maigne syndrome, neuropathies of T12 posterior ramus and posterior cutaneous perforating nerve, middle cluneal neuropathies S2,3,4, 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 essentially a clinical, "bedside" diagnosis that is best confirmed using neurophysiological testing. Imaging techniques do not help make a diagnosis. Abdominal and pelvic CT scans are helpful only for exclusion purposes. MRI of the lumbar and sacral spine are rarely useful but should be done before surgical interventions.

Neurophysiological Testing: Neurophysiological tests have been used in the workup of pudendal neuropathy. Quantitative thermal sensitivity testing may be performed.[12] Two devices: The NTE – 2C and thermosensory tester, or the MSA thermal stimulator, are non-invasive and easy to use in a provider's office.[13] The pudendal nerve terminal motor latency test (PNTML) has been used for diagnosis and monitoring treatment results.[14] It can be performed in the provider's office. It 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 is measured at the anal sphincter. Axonal damage and demyelination can be identified. Postoperative normalization of the PNTML has been measured following decompression surgery in women with stress urinary incontinence. The PNTML only measures motor function in the inferior rectal nerve. 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, providers and patients find it a painful experience compared to the PNTML and the WDT.

Somatosensory evoked potential (SSEP) testing has been used to confirm pudendal neuropathy. SSEP is also a valuable tool to limit pudendal nerve damage caused by compression of the perineum caused by traction during hip surgeries.[15][16]

Some authors suggest the use of pudendal nerve blocks as a diagnostic tool.[17] However, in the literature, up to 20% of such blocks may be of poor quality and fail to provide pain relief.[18] Therefore, only 80% of patients would be diagnosed with pudendal neuropathy in this way. Moreover, patients with organ symptoms, but without pain, would be excluded from having their diagnosis made by this modality. Of importance, stimuli from the neurophysiologic testing often reproduce indicators of central sensitization (e.g., pain in a toe from stimulus to the labium or contralateral inguinal pain during the PNTML).

Treatment / Management

Patients with pudendal neuralgia (PN) are typically diagnosed after several years of symptoms, have seen multiple providers, and have undergone repetitive testing. They may have had several surgeries and are often told: "it is in your head." They suffer anxiety and depression. 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.

Because pudendal neuropathy is a tunnel syndrome, it is treated in a manner somewhat analogous to treatments for the carpal tunnel syndrome, namely:

  • Nerve protection and medications
  • Pudendal nerve perineural injections (PNPI) given as a series of three at four-week intervals
  • If conservative treatments fail, decompression of the pudendal nerve(s)

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.[19] 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. These scores are available in multiple languages.[20]

Nerve Protection

This is a patient-guided treatment of self-care. When pain occurs while seated, we recommend a simple "sit-pad" that can be self-constructed or purchased. With the center removed, the perineum has no pressure, and the patient is sitting on his/her ischial tuberosities. These pads are useful and may be curative. Cessation of hip flexion exercises, cycling, jogging, and sports activities are essential to prevent repeated PN injury. 

Medications

Polypharmacy is often necessary to control the multiple symptoms of neuropathic pain and central sensitization that is common in these patients. 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 of medications depending on treatment response and side effects.

Some commonly used medications include:

  • Gabapentin often started at 300 mg TID.
  • Amitriptyline often started at 10 mg HS, titrating every five days to a maximum of 50 mg HS as tolerated.
  • Clonidine 0.1 mg HS can be beneficial in controlling sympathetically maintained pain. Patients often find this is 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.

Choices of drugs to be used must take into account the patient's history of medication use and side effects.

Other Modalities

Physical therapy may be a useful adjunct for tender, spastic pelvic floor musculature and should be used for 6 to 12 weeks. Many additional interventions are found in the literature, some of which are specious. For instance, stem cell therapy should not be recommended for nerve compression.

Pudendal Nerve Perineural Injections (PNPI)

A series of three pudendal nerve blocks with a mixture of lidocaine 1% and bupivacaine 0.25% and a corticosteroid is used therapeutically. The blocks are given at four-week intervals. This regimen allows time for the beneficial effect of steroids to complement the early pain control from the local anesthetics. As the steroid benefit wanes, the next block is performed. Our experience using blocks at two and six-week intervals produced inadequate responses as measured by symptom scores.

Pudendal blocks can de be done without sedation using the transgluteal approach as described by Bensignor.[21] Two blocks are given into the interligamentary space between the sacrospinous and sacrotuberous ligaments immediately adjacent to the ischial spine. The location of the block is often aided by patient reports or pudendal symptoms when the needle is inserted. The third block in the series is given by an interventional radiologist using computer tomography (CT) guidance.[22] Alcock canal may be identified using contrast. Injections may be performed unilaterally or bilaterally as appropriate. Injections performed without sedation will allow for communication between the patient and interventional radiologist.

Patients are examined two hours after their block to determine the quality of the block via pinprick testing. Pain relief within minutes or a few hours from the local anesthetic confirms the diagnosis of pudendal neuropathy. Lack of any pain relief indicates that the block missed the pudendal nerve pathway. Relief from steroids usually occurs three to five days post block and lasts for three to five weeks. Transgluteal injections are preferred over vaginal injections to ensure higher precision in placement and to decrease the possibility of infection. Some providers perform PNPI using ultrasound guidance and nerve stimulator guidance. The use of MRI has also been reported.[23] 

Pulsed radiofrequency has been used as an alternative to PNPI.[24] Results are difficult to compare because some providers include local anesthetics and corticosteroids with the PRF. Sacral neuromodulation or spinal cord neuromodulation is considered treatments of last resort when all treatments, including nerve decompression, have failed to provide adequate pain control.  

Decompression Surgery

As with any tunnel syndrome, the pudendal nerve may require decompression surgery. Entrapment is only identifiable at the surgery. Indication for decompression is severe pain/symptoms that do not respond to nerve protection, medications, and a series of good quality PNPI. Robert, in France, developed the transgluteal approach that is most 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 the pudendal canal. Often an adhesion barrier is applied before closing. Hospitalization for 1 to 2 nights is common.

There are several perineal approaches for surgical decompression of the pudendal nerve. Shafik described the first perineal approach. One minimally invasive approach uses a urologic resectoscope.[25] Several case series report similar results between the various approaches.[26] A randomized control study published by Robert demonstrated the benefit of surgery over conservative care.[27] Laparoscopic decompression is another approach that is becoming more widely used.

The most common site for PN compression is in the interligamentary space between the sacrospinous and sacrotuberous ligaments. The second common site is in the pudendal canal. The falciform process may compress the nerve. Congenital compression may be due to aberrant fascias. The nerve may also be compressed between leaves or layers of the sacrotuberous ligament. Multiple anatomic variations of the pudendal nerve have been described.[28]

NIH-CPSI, used in the US and Belgium, has enabled a more objective comparison between surgical approaches and has demonstrated comparable surgical results with the transgluteal and the transperineal (resectoscope) approaches.

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

Differential Diagnosis

In males, the most common misdiagnosis of pudendal neuralgia (PN) is prostatitis. The National Institutes of Health attempted to clarify this issue by developing four categories of prostatitis, including “Chronic Pelvic Pain Syndrome” or CPPS, as one of the categories.[29] Providers should rule out inflammation in the prostate by examining prostatic secretions or seminal fluid for white blood cells. The European Association of Urology lists 23 syndromes that present with chronic pelvic pain.[17] Each of these, including interstitial cystitis, could be considered to be in the realm of pudendal neuropathy. 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 may be considered. A diagnosis of ”endometriosis” is often made even without laparoscopic confirmation. Anorectal pathology can be diagnosed by physical examination.

As previously discussed, several other abdominal and pelvic neuropathies that overlap with the pudendal territory or can be referred to that territory should be considered and excluded.

The Nantes criteria have been published to guide the diagnosis of pudendal neuropathy. However, many international experts find several errors in them and do not recommend them.[7]

Prognosis

The sequential treatment of pudendal neuralgia (PN) relieves or reduces symptoms in most patients. After PNPI, pain reduction usually permits a normal lifestyle. Complete cures over 12 years have been reported. Although there are occasional reports of immediate and total relief following surgery, most authors report pain/symptom control over 6 to 24 months or longer. Therefore, a post-operative treatment program should be established. 

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

  • The degree of nerve injury and duration of compression
  • Failure to understand that the persistence of symptoms is a consistently reported part of the normal healing process
  • 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 require treatment
  • Iliohypogastric and ilioinguinal neurectomies may be necessary to eliminate inguinal/lower quadrant pain

The leading cause of recurrent symptoms of PN is the early resumption of the activities, which aggravated the condition, such as cycling, exercising, jogging, prolonged sitting. Postoperatively, after the sacrospinous ligament has been removed and the “lobster claw” released, the Valsalva maneuver during squatting to lift may force the pelvic floor to compress the nerve against the sacrotuberous ligament.

Complications

During nerve protection, some patients will develop pains in their feet as they stand for long periods rather than sit. Medication side effects are common and require alternative medications.

Pudendal nerve blocks may have side effects from steroids such as agitation and anxiety and elevated blood glucose in diabetics. Placement of the needle for injection may penetrate the nerve, a rare complication causing pain immediately that may last for up to six weeks or longer. Intravascular infiltration of lidocaine and bupivacaine is rare. Initially, the patient may notice a metallic taste. A large bolus can cause significant cardiovascular problems (which we have not witnessed in thousands of blocks). Aspiration of the injection needle for evidence of blood is not a uniform indicator of safety. Following the infiltration of medicines, transient exacerbation of pain may occur. We conjecture that it is because of the cold medications (room temperature) or local pressure of the volume of the bolus.

Surgical complications specific to pudendal decompression include injury to a small branch of the nerve. The microsurgical repair can be accomplished. An incomplete transaction of the sacrospinous ligament has been reported. In one of the author's experiences, transection of the sacrotuberous ligament resulted in the development of an unstable pelvis in one patient (out of several hundred). This is now avoided by using a midline vertical incision in the sacrotuberous ligament. Immediate, total pain relief is unusual. Pre-operative pain, slowly decreasing over several months, should not be considered a complication.

Deterrence and Patient Education

Prevention of pudendal neuralgia (PN) begins when the diagnosis is made. Sports medicine providers, personal trainers, coaches and the exercise enthusiast themselves need to 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 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 PN as a possible diagnosis in patients with bladder and bowel dysfunction and 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 sit-pad, and controlling stress. Patients must be reminded of the benefits of (non-opioid) medications in the reduction of the deleterious neuritic signals.

Enhancing Healthcare Team Outcomes

Because most providers are unaware of the existence of pudendal neuralgia (PN), chronic pelvic pain remains a morass of opinions, multiple tests, and various interventions.

End-organ specialists need to be aware of PN and consider this diagnosis in patients seen for bowel, bladder, and sexual dysfunctions. Often pain specialists focus on interventional spinal pain control. Patients would benefit enormously if primary care providers and internists developed an awareness of PN. Neurologists need to play a role. An integrated team, including a psychologist and a physical therapist in addition to the treating provider, is valuable.

Academic institutions need to show leadership in organizing a team approach. Uniform diagnostic techniques, monitoring, and interventions should be developed. Using uniform symptom scores would aid in the comparison of pre and post-treatment studies. Pelvic pain clinical research projects should evaluate for PN and consider this as part of the inclusion or exclusion criteria.


References

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