The pudendal nerve can be compressed in various locations along its course. The nerve runs between the sacrospinous and sacrotuberous ligaments, for instance, and entrapment between these two ligaments is probably the most common cause of pudendal neuralgia. This is where the nerve is compressed by the suturing of mesh placed during prolapse/incontinence surgery.
Another area of compression is Alcock’s canal; entrapment here is characteristic of pudendal neuralgia following vaginal childbirth. Compression also can occur where the clitoral nerve continues underneath the pubic ramus to the clitoris; this is typically where the nerve is compressed by a bicycle seat.
Diagnosis
The most important element of the diagnosis of pudendal neuralgia is the history, particularly regarding the onset of pain, the location of pain, and the nature of symptoms.
History and physical examination both are important for ruling out other reasons for pain, including vulvodynia, pelvic floor tension muscle spasm, and interstitial cystitis. A pelvic exam often will reveal significant tenderness in the pelvic floor muscles, especially in the area of the sacrospinous ligaments. Patients with pudendal neuralgia often have a trigger point – a place of maximal tenderness and pain – at the ischial spine. Palpation of this area to produce what’s known as a Tinel’s sign (with pain and symptoms) thus should be part of the exam.
Also key to diagnosis are computed tomography–guided blocks of the pudendal nerve. In our practice, we consider any degree of pain relief, for any duration of time after the block, as supportive of a diagnosis of pudendal neuralgia. Patients who do not experience immediate relief from a block are thought not to have the condition. These image-guided blocks must be performed by experienced interventional radiologists with a local anesthetic.
To date, there are no imaging studies that are reliable for diagnosis. Ongoing advances in magnetic resonance imaging (MRI) and magnetic resonance neurography (MRN) may make these modalities valuable in the future, but currently these techniques yield too many false negative results. Pudendal nerve motor terminal latency, which measures the conduction velocity of electrical impulses, is not useful given a high rate of intra- and interobserver variability and variations among patients who have had previous vaginal deliveries or pelvic surgery. Sensory threshold testing also has questionable reliability.
Initial Treatments
The initial approach to pudendal neuralgia should be conservative. Surgical decompression is the treatment of choice in patients with likely nerve entrapment, but determining the likelihood and extent of entrapment is a process. First, time must be spent in trying to identify and address the factors causing pain, and in trying to break the vicious cycle that occurs when neuropathic pain causes spasm of the pelvic floor muscles, which in turn leads to increased compression of the nerve and subsequent increases in pain levels.
While there are no official treatment algorithms, we have found – based on available data and our experience in treating more than 500 patients with pudendal neuralgia – that particular therapies can lead to marked improvements for many patients.
For some patients, especially those in whom bicycling or specific exercises initially caused the pain, avoidance of activities that worsen the pain, and other lifestyle modifications, can be helpful. Medical therapy with analgesics/pain management (such as oral pregabalin) and muscle relaxants also may be helpful for some patients. We have tried all kinds of muscle relaxants and have found that a vaginal suppository combining diazepam and baclofen is superior.
The most important treatment modality, however, is pelvic floor physical therapy. Such therapy is key because many patients have significant muscle spasm and subsequent muscle shortening. Therapists who are specially trained to work with pelvic floor muscle dysfunction can address these and other problems largely through various hands-on techniques, exercises, stretching, and education. Therapists can be identified on the International Pelvic Pain Society’s website, www.pelvicpain.org.
Botulinum toxin A (Botox) injections also are often a key part of therapy for patients with significant muscle spasm. In our practice, we administer approximately 200 units in 20 injections using a pudendal nerve block needle, under anesthesia. Not only does the treatment aid in muscle relaxation (thus increasing the patient’s tolerance to physical therapy), it also helps to differentiate between pain caused solely by muscle spasm, and pain caused by nerve injury and muscle spasm.
While patients who do not have neuralgia whose pain is caused solely or almost solely by muscle spasm will benefit significantly more from Botox injections, some patients with pudendal neuralgia will benefit from occasional, repeated Botox treatment in lieu of surgical decompression therapy. Many of our patients have been receiving Botox injections every 3-4 months, for instance.