Pudendal neuralgia caused by pudendal nerve entrapment (PNE) is a chronic and severely disabling neuropathic pain syndrome. It presents in the pudendal nerve region and affects both males and females. It is mostly underdiagnosed and inappropriately treated, and causes significant impairment of quality of life.
Anatomy of the Pudendal Nerve:
The pudendal nerve emerges from the S2, S3, and S4 roots' ventral rami of the sacral plexus. It carries sensory, motor, and autonomic fibers, however an injury to the pudendal nerve causes sensory deficits more than motor. It courses between two muscles, the piriformis and coccygeus muscles. It departs the pelvic cavity through the greater sciatic foramen ventral to the sacrotuberous ligament. At the ischial spine level, it passes medial to and under the sacrospinous ligament to re-enter the pelvic cavity through a lesser sciatic foramen. The pudendal nerve then courses in the pudendal canal, which is also called the Alcock canal. The three last branches of the pudendal nerve terminate in the ischioanal fossa. These are the inferior rectal branch, perineal branch, and dorsal sensory nerve of the penis or clitoris. However, there are case reports which have shown variability in the anatomy of the pudendal nerve.
The pudendal nerve entrapment syndromes subdivide into four types based on the level of compression.
Pudendal neuralgia can arise from mechanical or non-mechanical injury. The mechanical injury can be due to compression, transaction, or stretching. Amongst the mechanical causes, compression caused by PNE is the most common cause. The non-mechanical causes of pudendal neuropathy include viral infections (herpes zoster, HIV), multiple sclerosis, diabetes mellitus, and others.
The first reported case of pudendal neuralgia was due to cycling, which results due to continuous pressure on the Alcock canal.
The causes of pudendal neuralgia are:
PNE is a rare syndrome, and the prevalence is unknown. The incidence of this condition as estimated by the International Pudendal neuropathy foundation is 1 per 100,000, but the actual incidence might be higher than reported.
The presenting features of PNE are discussed below
The physical examination in patients with PNE is relatively normal except for pain reproduction. The symptoms depend on the site of entrapment. If the nerve gets entrapped at the ischial spine or the sacrospinous ligament, it causes pain medial to the ischium. Similarly, tenderness over the greater sciatic notch results when the nerve gets entrapped at the greater sciatic notch. Entrapment at the piriformis leads to spasm and tenderness of piriformis muscle. Lastly, entrapment at the Alcock canal and obturator internus result in tenderness and spasm of the obturator internus muscle.
In some of the cases, a transrectal or transvaginal examination might be included in the patient examination to exclude intrapelvic entrapment.
Pudendal nerve entrapment is a potentially challenging condition to diagnose because there are no specific diagnostic tests. The clinician needs to realize that it is exceedingly mandatory to get a thorough history and perform a detailed physical examination to reach a diagnosis. Dr. Roger Robert published the Nantes criteria to diagnose PNE and appears in detail below. This criterion has validation by many European physicians who have ample experience treating similar conditions.
Complementary diagnostic criteria:
The following tests can help in the diagnosis:
There are no specific and consistent radiological findings in patients with PNE, and further research is necessary.
If the patient fulfills Nantes criteria, no further investigation is needed to make the diagnosis. However, if the patient lacks any of the criteria, further evaluation should be pursued. MRI helps to rule out other causes of chronic pain in such cases.
The treatment options are as below:
Since there is no confirmatory diagnostic test, pudendal neuralgia is a diagnosis of exclusion. Other conditions merit consideration before making a final diagnosis.
Pudendal neuralgia due to PNE affects the quality of life immensely. However, it doesn’t affect life expectancy.
The complications associated with pudendal nerve block are:
Patients should be educated to avoid painful stimuli and actively participate in physiotherapy. Lifestyle modifications are one of the essential elements of the treatment plan.
It is crucial to understand that all types of pudendal neuralgias are not the result of PNE in the treatment planning of patients with chronic pain. It is essential to realize that the pudendal nerve can get trapped at different locations, and therefore, all patients will not benefit from the same therapy. Patients with chronic pain syndromes tend to get frustrated with multiple failed treatments and can be clinically depressed as well.
A study was conducted by Raynor et al. on 1024 patients to study the prevalence of depression in patients with chronic pain and its impact on health care cost. They categorized 60.8% of patients of chronic pain into probable depression and 33.8% into severe depression based on a questionnaire survey. They also reported higher health care cost amongst patients with depression (p=0.001). Similar results can be seen in data analysis by the medical expenditure panel survey of 26671 patients from 2008 to 2011. The research found that different levels of pain interference increase the total health care cost.
Chronic pain poses a mental and economic burden on the patient. These aspects should be considered when providing care to patients.
Pudendal neuralgia due to PNE is a rare neuropathic condition. It causes a significant impairment of quality of life. It often does not get diagnosed in a timely manner, and most patients get treated for other conditions. Thus Nantes diagnostic criteria were established and validated by an interprofessional team to aid in the diagnosis and further treatment of such patients. If the patient fulfills Nantes criteria, no further investigation is required, however, if any of the criteria are not present, the patient should be further evaluated, and MRI is generally done to rule out other causes of chronic pain. Individualized treatment is necessary. It typically requires permanent lifestyle changes and physical therapy. The treatment options include pharmacological therapy, CT guided blocks, decompression surgery, and neuromodulation.
A well-coordinated interprofessional healthcare team comprised of a pain physician, surgeon, anesthesiologist, nurse, radiologist, and physiotherapist to help in physical rehabilitation, is necessary to treat this challenging neuropathic syndrome. All these disciplines need to collaborate across interprofessional boundaries to optimize care and outcomes. [Level V]
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