PN Diagnosis Decision Path

By Jack Harich - August 29, 2002

The above diagram summarizes current best practices in diagnosis of PN to the PNE first surgery step, using the Dr. Robert protocol. Please note this is a very high level summary, and so omits many of the steps and questions you will encounter with your doctors.

Nerve Blocks

Generally the first nerve block is at the ischial spine, because this is the most common point of entrapment. If the pain goes away then you can be 100% sure the pain is from an area served by the nerve at or below that point, or is from the nerve itself. To determine whether it's the nerve or not, various tests to rule out non-PN causes of pain must be done. These can be done before or after a nerve block. The diagram shows them done before, since most of these various tests are cheaper and more routine than a nerve block. For example, my ischial spine nerve block in Houston on March 18, 2002 cost $1,800.00. The same test in Nantes at that time was about $350.00.

The ischial spine location has another advantage: it's about as high as you can go on the pudendal nerve before encountering the pudendal plexus. Above that, a nerve block would be somewhat useless, since that's where the pudendal nerve starts. See Pelvic Wall Blood Vessels and Nerves for where the pudendal plexus is.

If two or three nerve blocks with steroids (also known as corticoids) fail to give lasting relief at the ischial spine, the pudendal canal (Alcock's Canal) is tried. Other locations may also be tried. Dr. Robert cautions that:

"Two or three infiltrations are performed [at a single location]; this number should not be exceeded for fear of deterioration in the nerve trunk." - Source: PNE by Dr. Robert.

If an ischial spine nerve block has no effect on the pain, and the pain is in an area served by the pudendal nerve below the block location, then either the block was given incorrectly, or PN is not present. As Dr. Robert wrote in an email to a patient:

"The main problem arises for patients without any effect after blocks. I do believe that then they are not candidates for surgery." - Source.

However, most rules have exceptions. In a very small percentage of cases, a nerve block will not temporarily reduce or eliminate PNE pain. This can occur when the pudendal nerve has an unusual route, such the "rose petal" shape Dr. Robert found in one patient. There can be other reasons. Since even nerve blocks are not 100% reliable for testing, diagnosis must rely on a suite of tests.

The PNLT

Of interest is the Pudendal Nerve Latency Test (PNLT) is not required for diagnosis of Pudendal Nerve Entrapment (PNE). I have confirmed this with Dr. Ken Renney, who approved the following paragraph on June 17, 2002:

"If the PNLT tests high, damage is evident and treatment is less likely to completely cure the condition. If it tests medium, treatment is much more likely to be effective since less damage is present. If it tests normal, treatment has excellent potential, since motor latency damage has not yet occurred."

This assumes, of course, that the PNLT is administered correctly. It is a difficult test to do correctly, so that the results can be reliably compared to standard results. According to Dr. Ken Renney (as of June, 2002), only two doctor teams in the world are trained to do the PNLT correctly: the Nantes and Houston teams. All others use what Ken calls the "classical" technique which does not get "good waveforms." This may change in the future.

The value of the PNLT lies in confirming (a second indication) that pudendal nerve damage is present and how much. This gives the surgeon a strong clue of what to look for when they get inside. Multiple indications are much more reliable than a single indication.

The quote about PNLT outcomes should help to convince you to seek diagnosis and treatment immediately, before further damage occurs. It should also convince you to avoid making your condition worse.

Confirmation Tests

If the same team of doctors that will be doing the surgery has been doing the preliminary tests, there may be no need for final confirmation tests. This is the case for the team of Dr. Robert (really Professor Robert), Dr. Labat, and Dr. Bensignor, because they confer closely during the diagnosis stage. However, if you are in the US and get your initial nerve block(s) there, confirmation testing is done in France. This allows the French doctors to proceed with confidence and more complete knowledge.

Also, if the team doing the surgery trusts previous tests, they may proceed with surgery with no additional tests.

The rest of the diagram is self explanatory.