In Chronic Pelvic Pain, Consider Pudendal Neuralgia
by Clayton Simmons
ISSUE: JUNE 2010 | VOLUME: 8:06
Pudendal neuralgia may represent a promising, although complex, avenue for understanding and treating certain forms of chronic pelvic pain.
In a presentation at the annual meeting of the International Anesthesia Research Society in March, John S. McDonald, MD, chair of the Department of Anesthesiology at Harbor-UCLA Medical Center, Torrance, Calif., offered insights into the treatment of chronic pelvic pain (CPP) generally and urged physicians to be alert for pudendal neuralgia, an etiology that may be overlooked in evaluating patients presenting with this kind of pain.
CPP may signal a variety of conditions. Some are well known, such as endometriosis and interstitial cystitis. But pudendal neuralgia, which may involve damage to or compression of the pudendal nerve, can also cause CPP and is less well understood, Dr. McDonald told Pain Medicine News.
Differentiating pudendal neuralgia from other conditions can be challenging. When patients present with symptoms of CPP, many physicians use magnetic resonance imaging to identify causes such as endometriosis or ovarian cysts, and if present, to recommend surgery or other treatment, according to Dr. McDonald. Pudendal neuralgia, however, may coexist with these or other conditions, leaving persistent pain even after surgery.
Common symptoms suggesting pudendal neuralgia include pain when sitting and pelvic floor dysfunction, pain during and after sexual activity and bowel movements, and pain originating in the inferior hypogastric plexus together with frequent need to urinate, Dr. McDonald noted. In conducting a differential diagnosis, physicians must carry out a pelvic exam and often perform diagnostic pudendal nerve blocks, challenging procedures that may require consultation with a gynecologist. For this reason, Dr. McDonald suggests referring patients reporting CPP to a specialist in pelvic pain.
Several treatments for pudendal neuralgia exist. Anticonvulsants or antidepressants may be effective for this as for other neuropathies, and Dr. McDonald’s research indicates that local anesthetic nerve blocks represent another option. A 2000 study by Dr. McDonald of 26 women showed that repeated local anesthetic block of the pudendal nerve may relieve pain if appropriately placed (Obstet Gynecol 2000;95:306-309). Other physicians have explored surgical options, which aim to decompress the pudendal nerve.
Although the etiology of pudendal neuralgia is not entirely clear, research points to demographic risks and potential contributing factors. While prevalence in the general population is unclear, it is far more common among women than men, possibly because labor and endometriosis may damage the pudendal nerve. Among men, bicycle riders seem to be at particular risk, Dr. McDonald said, perhaps owing to poorly designed bicycle seats.
Animal studies indicate more detailed pathophysiology, although results require confirmation and further explanation. Reduced oxygen flow to the pudendal nerve may cause trauma associated with pudendal neuralgia, according to some research. A study in rats co-authored by Dr. McDonald and presented at the Western Anesthesia Residents Conference in 2007 indicates that pudendal neuralgia may lead to referred pain, which conceivably complicates the diagnosis in humans. In this study, innervation of the pudendal nerve seems to cause innervation that presents as bladder pain. “Symptoms like these may be labeled as interstitial cystitis” and be misdiagnosed, Dr. McDonald told Pain Medicine News.
Fred Howard, MD, associate chair of the Department of Obstetrics and Gynecology at the University of Rochester Medical Center, in New York, noted that pudendal neuralgia is “not terrifically well known” among physicians. It is, he agreed with Dr. McDonald, “a real challenge to diagnose.” Conversely, he cautioned that increased attention to its existence and characteristics may lead to overdiagnosis.
Dr. Howard stated that unilateral pain, especially when sitting, combined with hyperalgesia and allodynia, may be tip-offs to pudendal neuralgia. Interstitial cystitis presents with very similar symptoms, however, and he suggested that pelvic exams require a specialist’s expertise.