Diagnostic path.
The sacrum, by virtue of its anatomic location, is a structure
that presents itself to the attention of multiple medical
specialists. This is why many people with this type of pain
will 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
(also known as “pudendal neuropathy” or “pudendal
nerve entrapment”) are still search for answers within
the medical system. Many are being misdiagnosed over and over,
some even having inappropriate and unnecessary surgeries.
Additionally, many are being labeled by doctors who cannot
figure out what is wrong with them as “head cases”,
and are sent off to psychiatrists.
This page is aimed at giving you a roadmap for a pudendal
neuralgia diagnosis. The predominant factor in the diagnoses
of pudendal neuralgia are the symptoms.
The clinical exam is rather poor. The most constant element
is a replication or worsening of the pain during a rectal
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. The doctor
should also look for the following signs:
Very often there are other painful areas in the surrounding
region (piriformis muscle,
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.
A clinical exam should be done first to rule out other
more conventional conditions such as prostatitis, vaginitis
or urinary infections. If the pain persists after the conventional
medication then the next steps in the diagnosis of pudendal
neuralgia can be pursued.
2- Magnetic resonance imaging (MRI) or
computerized tomography (CT Scan).
These devices cannot see the nerves. However, they are
the best imaging technology available today. They are used
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 or sacro-illiac
join disfunction SIJD have some symptoms that mimic PNE.
One should pass at least a CT scan or MRI from the S5 disk
to S1. In the case of pudendal neuralgia, CT Scan and MRI
exams will show no irregularities.
3- Pudendal Nerve Motor Latency Test (PNMLT)
A PNMLT is an electrophysiological 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. 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 into 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 for 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 affliction as well. So, an abnormal
PNMLT indicates that the pudendal nerve is affected but
a normal reading does not rule out PNE. In this case an
entrapment could exist even if the motor fiber of the nerve
has not been affected yet. This is more common with people
who have had PNE only for a short period of time and have
mid symptoms. Nevertheless, the PNMLT is the most accurate
neurological examination for the pudendal nerve.
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.
5- Diagnostic block.
A diagnostic block, or a "blockage of the nerve",
is an injection with a local analgetic such as lidocaine
or one of its derivatives (also used by dentists). The block
is usually given through 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 analgetic persists, this is an indication that your
pudendal nerve is being compromised in some fashion, and
that possibly some damage to the nerve has occurred.
Injections can serve as diagnostic tool but can also serve
as a therapeutic tool. In the latter case, the injection
consists of steroid. See Treatments for more information.
These injections must be given only under strict radiological
control for safety reasons since the exact placement of
the needle is critical in confirming the diagnoses, or even
possibly curing the patient. Injections at the ischial spine,
can be done under fluoroscopy or CT scan while the final
injection done into alcock’s canal must be done under
CT guidance only. The complete “how to” guide
for pudendal nerve injections for the radiologist can be
found here.
In search for a diagnoses
The final diagnoses of pudendal neuralgia is based on a
persona having at least two out of the three criteria:
- typical PNE symptoms,
- an abnormal electrophysiological test
- a positive response to the diagnostic (analgetic) nerve
block.
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1. The clinical exam 
