Diagnosis

Diagnosis
Overview
The sacrum, by virtue of its anatomic location, is a structure that presents itself to the attention of multiple medical specialists. This is why people with chronic pelvic pain will often visit many gynecologists, urologists, imaging specialists, gastroenterologists, neurologists and pain specialists before finding the correct diagnoses.
Pudendal neuralgia is a rare condition, and it is seldom diagnosed correctly in a short period of time. Sadly, many people with pudendal neuralgia (PN), pudendal neuropathy (PN), or pudendal nerve entrapment (PNE) are still searching for answers within the medical system. Many are being misdiagnosed over and over, some even having inappropriate and unnecessary surgeries. Sadly, many are being labeled by doctors who cannot figure out what is wrong with them as “head cases” and are sent off to psychiatrists.
The diagnosis is usually made based on the patient’s symptoms, history, and exclusion of other illnesses such as infection or tumor. While no test is 100% accurate some of the more commonly used tests are the pudendal nerve motor latency test (PNMLT), electromyography (EMG), diagnostic nerve blocks, 3T MRI using special software and settings, and magnetic resonance neurography (MRN). Pudendal neuropathy can occur in men or women although about 2/3 of patients are women. It is considered rare and many doctors are just now becoming aware of this illness. Sometimes it is referred to as cyclist’s syndrome, pudendal canal syndrome, or alcock’s syndrome. Pudendal neuropathy can have similar symptoms to another disease or be misdiagnosed as another disease. Those most often associated with or confused with PN are chronic non-bacterial prostatitis, levator ani syndrome, proctalgia fugax, interstitial cystitis, vulvodynia, vestibulitis, chronic pelvic pain syndrome, hemorrhoids, piriformis syndrome, coccydynia, ischial bursitis, idiopathic (of unknown cause) orchialgia, or idiopathic prostadynia.
This page is aimed at giving you a roadmap for a pudendal neuralgia diagnosis. The predominant factor in the diagnosis of pudendal neuralgia is the symptoms.
How is PN correctly diagnosed?
Correct diagnosis follows these main stages:
A. The exam.
For guys the exam should include digital rectal exam. For ladies the exam should include a pelvic exam.
What is your history? Were you exercising heavily, did you have an accident, pelvic surgery, vaginal delivery, or were you sitting long hours? Is your pain in the distribution area innervated by the pudendal nerve? Is there increased pain or tenderness when your doctor presses along the course of the nerve via the rectum or vagina? The most constant element is a replication or worsening of the pain during a rectal/vaginal touch at the ischial spine area. This touch must be done by the end of the finger on the postero-lateral wall of the rectum for men or the side of the vagina for women at the ischial spine and alcock’s canal.
Very often there are other painful areas in the surrounding region such as the piriformis muscle or tailbone pain. Most of the time this is a reaction to the nerve pain but in some cases the piriformis muscle could pinch the nerve and be the main cause.
B. Elimination of other factors.
It is important to rule out other problems such as urinary tract infections, prostate infections, vaginal infections, or sexually transmitted diseases. If the pain persists after the conventional medications to treat these illnesses are tried then the next steps in the diagnosis of pudendal neuralgia can be pursued. Disorders that might cause peripheral neuropathy such as Lyme’s disease or multiple sclerosis should also be ruled out. You should have a stool examination for possible blood. (Screen for colorectal cancer and other problems.) Guys should have a PSA.
C. Magnetic resonance imaging ( MRI), CT scan, and magnetic resonance neurography.
Often the pudendal nerve expert doctors recommend an MRI to rule out obvious problems such as tumors or spinal abnormalities. Most MRI’s and CT scans cannot see the nerves but they are important to exclude any other organic lesions or to find other causes of nerve compressions especially at the level of the spine. Many other conditions like cauda equina syndrome and arachnoiditis have some symptoms that mimic PN. One should have at least a CT scan or MRI of the lumbosacral area and lumbosacral plexus. Often with pudendal neuralgia, CT scan and MRI exams will show no irregularities. The PNE doctors each have their own protocol so while it is OK to have these tests locally, before scheduling your MRI it is good to check with the PNE doctor you may eventually wish to see so that you know exactly what type of MRI they require. This can help you avoid having an MRI twice.
A 3 Tesla MRI using special settings and protocl may give clear enough images to see nerve entrapments in some cases. Magnetic resonance neurography (MRN) is similar to an MRI but it uses special software to enhance the image of small nerves that are difficult to see on a regular MRI. There are only a handful of centers in the world where you can have these tests and entrapments do not always show up so the test is only accurate for a diagnosis of PNE part of the time.
D. Pelvic floor physical therapy that includes myofascial release.
If your doctor decides your problem might be PN often they will refer you to a physical therapist for pelvic floor physical therapy. It is difficult to distinguish between pudendal nerve entrapment (PNE) and pelvic floor dysfunction (PFD) because typically PNE can cause PFD and the symptoms can be similar. A course of pelvic floor physical therapy can help to determine if you just have PFD. People with PNE are less likely to have good results from pelvic floor physical therapy.
When choosing a pelvic floor physical therapist it is important to make sure you receive the correct type of PT. Typically the pelvic floor muscles are overly tense (contracted) and they need help to relax (lengthen). For this reason pelvic floor strengthening exercises such as Kegals are not recommended for people with PN. Myofascial release and trigger point therapy are recommended to retrain the muscles to relax.
E. Electro physiological testing including EMG’s and PNMLT.
A PNMLT is an electro physiological procedure, similar to an EMG (electromyogram), which measures the speed of nerve conduction. This exam is done by a neurologist. Not all neurologists have the necessary equipment to do this type of examination on the pudendal nerve. During this exam, the pudendal nerve is stimulated electrically inside the rectum (or vagina) at the ischial spine with electrodes on the tip of a special glove. The speed of the nerve conduction is recorded by a small needle inserted in the perineum. If the nerve responds slower than normal, this gives an indication that the nerve may be entrapped or damaged.
The PNMLT examines only the motor function of the nerve. There is no way to test the sensory fibers of the nerve which transmit pain. The reason for the test is based on the assertion that an abnormal motor function will most likely conceal a sensory affection as well but this is not always true. So, an abnormal PNMLT indicates that the pudendal nerve is affected but a normal reading does not rule out PN. In this case a sensory neuropathy could exist even if the motor fiber of the nerve has not been affected yet. This is more common with people who have had PN only for a short period of time.
The neurological examination can be completed by the measurement of the anal reflex latency, measurements of the bulbocavernosus reflex latencies (BCRLs), somatosensory evoked potentials of the pudendal nerve (SEPPNs) and the sensory conduction velocity of the dorsal nerve of the penis (SCVDNP). Those exams can give further information about the condition of the nerve or the origin of the pain.
Results of these tests are not 100% accurate for a diagnosis of pudendal neuralgia or PNE but they can help add to the overall picture as to how well the nerve is functioning. Sometimes, although not always, there will be a latency with the EMG and PNMLT testing that indicates a neuropathy. There are some doctors who rely mostly on the PNMLT and there are others who rely mostly on the EMG. Some doctors feel that utilizing the EMG, they can actually "tell" where the entrapment is.
More about the PNMLT
The full name is the pudendal nerve distal motor latency test. As the "Consensus Statement of Definitions for Anorectal Physiology and Rectal Cancer" for the United States defines it:
"Pudendal nerve latency is the measurement of the time from stimulation of the pudendal nerve at the ischial spine to the response of the external anal sphincter. Normal pudendal nerve terminal motor latency is <2.2 ms."
This means the normal response time should be 2.2 milliseconds or less. Other points besides the ischial spine can be used for the test, which will cause a different response time. Dr. Robert's approach uses several different points. The most common has a normal latency of 4.0 ms or less. As an example of PNMLT scores one patient’s results at Dr. Robert's hospital were 4.7 ms left and 7.8 ms right.
Anything over the normal latency time means the nerve is not operating normally and is therefore probably damaged leading to motor dysfunction of the nerve. The pudendal nerve is found in the pelvis.  Right and left branches of this nerve extend to the bladder and bowel sphincter muscles.  When the nerves and muscles perform normally, we have control of bladder and bowel functions without discomfort.  A problem with pudendal nerve function may lead to loss of control of the anal sphincter muscles.  Such problems may cause leakage of urine or stool, conditions referred to as urinary incontinence and bowel incontinence.  Problems with pudendal nerve and sphincter function may also cause chronic constipation or rectal pain.
The PNMLT does not measure the sensory function of the nerve but only measures the motor function of the nerve. So PNMLT scores do not necessarily correspond to pain levels. A recent publication reports that the PNMLT is not a good indicator of whether you have an entrapment but it may indicate a neuropathy.
Description of the PNMLT
The most widely used method of electro physiological testing of pudendal nerve function is that described by Kiff and Swash at St. Mark’s Hospital in London. They used a rubber finger stall that has two stimulating electrodes at the tip and two surface electrodes for recording mounted three cm. proximally at its base. The index finger, mounted with the device, is inserted into the rectum and placed on the ischial spine. Electrical stimulation is then initiated and the latency of the response to the anal sphincter is recorded on surface or needle electrodes. The normal mean terminal latency is 2.0 +or – 0.3 msec. It must be pointed out that the pudendal nerve terminal motor latency test (PNTML) is solely a motor study, and is of importance only if the study is abnormal. In other words, the sensory nerve fiber component of the nerve more peripherally located can be compromised without involving the motor fibers. This anatomical situation can result in a patient with sensory fiber compression and pain having a negative PNTML test. In addition the test does not indicate the extent of injury or entrapment, but only if the nerve is responding abnormally. A comprehensive examination should include sensory nerve tests; as well as testing of the components of motor function, and EMG of the pelvic floor. With this information one could ascertain the severity of the damage i.e., if there is axonal damage or focal demyelization, determined by the motor amplitude and EMG characteristics; if the process is of recent or longstanding; and if there is an attempt to regenerate (needle EMG). Dr. Benson has developed a sensory testing method, based on the bulbo/clitorocavernosus reflex, in which a mild stimulus is applied to the glans penis or adjacent to the clitoris and the reflex conduction time to the pelvic floor muscle is measured. (Weiss, page 14)
 
PROCEDURE :  You will be asked to undress from the waist down, and wear a patient gown with the opening in the back.  A technologist trained in performing this exam will be conducting the test, and will explain everything he or she is going to do.  You will be asked to lie on a stretcher, turn to your left side, and bend your knees.  An electrode pad (similar to an EKG pad) will be placed on your buttock or thigh.  The technician will then put on a rubber glove with an electrode on the index finger.  After lubricating his index finger, he will gently insert it into your rectum.  This should be no more uncomfortable for you than a rectal exam.  The technologist will then send a mild, electrical stimulus through the electrode on his finger to your pudendal nerve.  This stimulation may cause the muscles of your thigh to twitch involuntarily.  The technologist will then gently rotate his finger to repeat the test on the opposite branch of the nerve.  A computer will record the response of your pudendal nerve to the stimulation.  A physician will interpret the results and determine if any nerve conduction delays exist.  The actual procedure will take 15-20 minutes. 
 
This is a picture of the St. Marks electrode that is used to conduct the PNMLT.
More about other electro physiological tests
Some pudendal nerve physicians perform electro physiological tests such as the sacral reflex test, cortical evoked potential test, and somatosensory evoked potential (SSEP) to test whether there is a problem in signals from the spinal cord and brain or in the motor responses of the pelvic floor . These tests usually require the use of electrodes or tiny needles inserted in muscles in the perineal area or in the forehead and small bursts of electrical stimulation. The tests can be slightly painful but do not last very long.
“An SSEP indicates whether the spinal cord or nerves are being pinched. It is helpful in determining how much the nerve is being damaged and if there is a bone spur, herniated disc, or other source of pressure on the spinal cord or nerve roots.” (see more information including source at the page on Spine Diagnostics SSEP)
Sacral reflex testing tests the motor response of muscles in the pelvic floor.
 “Sacral reflexes consist of motor responses in the pelvic floor and sphincter muscles evoked by stimulation of sensory receptors in pelvic skin, anus, rectum, or pelvic viscera. These responses may be elicited by physical or electrical stimuli.”(source)
One publication looks at the differences between the some of the more commonly used nerve tests.
Eric DeBisschop - Eric Bautrant
They look at "staged" sacral reflexes vs the Pudendal Nerve Motor Latency test. Many factors can interfere with nerve testing results. Examine with your doctor the pros and cons of using these tests.
F. Pudendal nerve blocks.
A diagnostic block, or a "blockage of the nerve", is an injection with a local anesthetic such as lidocaine or one of its derivatives (also used by dentists). The block is usually done in the buttock to reach the pudendal nerve at the ischial spine where it is most often entrapped between the sacrospinous and sacrotuberous ligaments. One block for each side affected is necessary. If the pain diminishes immediately or even vanishes completely as long as the effect of the local anesthetic persists, this is an indication that your pudendal nerve may be compromised in some fashion, and that possibly some damage to the nerve has occurred.
Injections can serve as a diagnostic tool but can also serve as a therapeutic tool. In the latter case, the injection consists of a steroid as well as an anesthetic agent.
If you experience significant pain relief for even a short time (several hours) from a nerve block that may mean you have pudendal neuralgia. However pudendal nerve blocks can temporarily ease the pain caused by other problems in the distribution area of the pudendal nerve so the nerve block is only one of the tools used in the diagnosis of PN.
In the context of PN, a nerve block involves injecting a liquid at a precise location near a nerve. For a small nerve like the pudendal that takes slightly different paths in different people, this requires more than just studying a person's body and deciding where to insert the needle, at what angle, and how deep. It requires imaging of some type, such as X-ray (fluoroscope), ultrasound, MRI or CT. Without the accuracy these imaging systems provide, it is difficult or impossible to know if the needle tip is located correctly. If incorrectly located, the nerve can be damaged or the injected liquid will be too far away to have its intended effect. Dr. Bensignor says the needle tip must be within one millimeter of the target. However, even with image guidance it is possible for the block to miss its mark.
There are two main types of injected liquids: a local anesthetic and slow-release steroids. The local is a short term diagnostic tool. If the pain goes away and stays gone for the short term, the location was correct and the nerve can be suspected of being a contributor or the sole source of pain. The steroids are a long term therapeutic attempt. In some cases they will cause the nerve, if it is irritated, to get better. This can take days or weeks, and improvement may be temporary or permanent. This delay explains why physicians prefer a delay of several weeks between nerve blocks with steroids. If the nerve is not irritated, the steroids have no effect. Some doctors use heparin, an anti-inflammatory medication, instead of steroids.
Two main locations are used. The ischial spine block is done by injecting into the sacrospinous ligament. Alcock's canal block is done by injecting into the sacrotuberous ligament. These are not the same as the blocks carried out for childbirth pain. In some cases the blocks may worsen the pain a little but this should last only a few weeks. In a few cases nerve blocks have caused a permanent worsening of pain possibly due to the nerve being “nicked” by the needle, a reaction to the medication, or formation of scar tissue.
When the nerve block is conducted under guidance, the patient is asked to lie down in the prone position. Using a small needle the doctor injects an anesthetic to numb the buttocks prior to injecting with the larger needle that targets the pudendal nerve. When the doctor is able to find the pudendal nerve, he will then inject either the local anesthetic and the long term steroid or heparin. The procedure itself lasts approximately 30 minutes. This is done on an outpatient basis. No overnight stay is required.
If the injection relieves your pain that is considered a positive response to the nerve block and the pudendal nerve may be the source of your pain. If the injection did not provide any relief there are two possible conclusions.
1. The pain is not as a result of the pudendal nerve or
2. The physician did not get close enough to the pudendal nerve to feel any effects.
After a pudendal nerve block it is possible to evaluate whether the block hit the target of the pudendal nerve by testing the perineum, clitoral, and anal areas for loss of sensation and numbness. Sometimes the physician might order another block four to six weeks after your first block, to make sure that they can entirely rule out pudendal neuralgia, by trying to see if they can get close enough to the nerve again.
Occasionally medication from the nerve block can wander into the area of the sciatic nerve making it difficult for the patient to walk. This problem typically subsides within 24 hours.
Pudendal neuralgia: CT guided pudendal nerve block technique - This highly technical 1999 article describes the anatomy involved and how to perform nerve blocks. As the article says, "Infiltrations are made first at the ischial spine. If two consecutive nerve blocks into the ischial spine fail, a third injection can be made into the pudendal canal.”
Below are some great pictures of what to expect when receiving a nerve block. The first picture is a CT guided photo showing the optimum placement of the needle in this particular person.
 
 
Here is what Professor Robert, one of the PNE experts, wrote in an e-mail about nerve blocks:
"Most of the time in fact the compression of the nerve trunk is at the level of the claw between the sacro spinal and the sacro tuberal ligaments. That is why I don't like to call this syndrome the Alcock syndrome, as far as mainly the compression is more important outside of the canal. Of course the Alcock tunnel syndrome does exist. That is why, according to the medical findings we start by blocks at the level of the claw. If it doesn't work then we do the second block in the tunnel. The block at the level of the claw is done under fluoroscopy. The other one is scan guided under CT view. Two blocks can be done at each level on one or both sides but no more."
"The second reason is that blocks constitute a very important diagnostic test. If they don't work at all we can suspect a bad diagnosis. If they do well for a while (several days or weeks) they must be done another time. The surgical indications arise from the failure of those blocks with time. The main problem arises for patients without any effect after blocks. I do believe that then they are not candidates for surgery. A block which may lead to disparition of pain during some hours is nevertheless a good diagnostic test for us and may lead to surgery. So, the guideline could be as follow: Blocks at the two levels without any efficacy = bad diagnosis. Blocks at one or two levels with "long improvement" (some days or weeks ) = try one block again at the two levels. If it doesn't work = surgery with very high hopes. Blocks with very short amelioration = surgery.”
In Conclusion
None of the diagnostic tests for PN and PNE are 100% accurate so the more of these tests you have the better your overall picture will be in determining your diagnosis.
The final diagnosis of pudendal neuralgia is based on a person having several or all of these criteria:
  1. Typical PNE symptoms
  2. An abnormal electro physiological test
  3. A positive response to the nerve block
  4. A distinct abnormality on a 3T MRI or an MRN
  5. Pain elicited upon pressing along the course of the nerve
  6. Elimination of other diseases being the cause