Differential Staged Sacral Reflexes: Methodology and Normal Values from 51 Healthy Subjects and 134 Patients with Pudendal Neuralgia

Objective: to develop a reproducible method for electrophysiological study of pudendal nerves which can explore the different risk areas: sacral spinal, infrap iriformis area and ischiorectal fossa. This method is called "differential staged sacral reflexes (DSSR) ". 51 patients not suffering from pudendal neuralgia and 134 patients with pudendal neuralgia have been selected. The sacral reflexes (SR) are made at the ventral and dorsal quadrants of the anal sphincter and at the pubococcygeus muscle. Considering the values of the DSSR obtained on healthy subjects and on patients with pudendal neuralgia, maximum threshold values have been established: a significant difference between ventral and dorsal quadrant of the anal sphincter: damage orientation at the level of the ischiorectal fossa; significant difference between dorsal quadrant of the anal sphincter and pubococcygeus muscle: damage orientation at the level of the infrapiriformis area. SR delayed uniformly at the three afore-mentioned muscles: damage orientation at the level of the sacral spinal. The DSSR allow in a reproducible way to investigate the pudendal nerve in all areas suitable to entrap this nerve, which is impossible with the method of pudendal nerve terminal motor latency (PNTML).


Introduction
The conventional technique of electrophysiology of the pudendal nerve is to measure the distal motor latency (PNTM L) [1] by endocavitary stimulation, rectal and / or vaginal, at the level of the ischial spine with collection at the anal sphincter This method sins however due to the lack of reproducibility and of sensibility [2][3][4][5]: PNTM L can be lengthened without corresponding to a pudendal neuropathy and being normal without eliminating it. Several factors can interfere with nervous time conductions: vascular, synaptiques distales endings, vegetative reactivities, variability of the answers in the time and according to the operator.
The sacral reflexes [6][7][8] studied on the ventral and dorsal quadrants of the anal sphincter and on the pubococcygeus muscle (staged sacral reflex) showed significant differences in responses to establish normal values, beyond and which according to the responses, a truncal compression (TC) or an intra-spinal conflict may be mentioned. In case of TC, these 2. Anatomical Recall (Fig. 1) The PN is a mixed nerve taking its origin at the S2, S3 and S4 roots, with a possible contribution of S1 [9]. Then, the PN cross the infrapiriformis area [10] limited fro m the lower edge of the piriformis muscle to the sacrospinous ligament (SSL). The PN then passes beneath the SSL. The inferior rectal nerve (IRN), the first collateral PN, born before the coming of the ischiorectal fossa (IRF), does not go under the falciform process (FP) or in the A lcock canal (A C). It will innervate the dorsal quadrant of the anal sphincter (AS). The PN truncal pathway, became perineal nerve (PEN), continues under the FP and the AC (duplication of the fascia of the Obturator internus). It will innervate the ventral quadrant of AS.
The levator ani nerve (LAN) runs up the anterior coccygeal muscle. It thus does not pass under the SSL or under the FP and thus avoids the AC. It innervates, among other things, the pubococcygeus muscle (PCM) [11].
Note that the PN has many anatomical variat ions: After dissection of the body 7 [7][8]: The origin of the IRN is in all cases before entering the ischiorectal fossa (IRF) with a direct path to the posterior of the anal canal, can Values from 51 Healthy Subjects and 134 Patients with Pudendal Neuralgia passes under/throught or above the SSL. Then it runs in the lateral space of the ischiorectal fossa nerve. It never passes in the AC (duplication of the fascia o f the Obturator internusl). After dissection of 37 bodies [12], it is found from a trunk under the SSL in 56.2%, 11% in two trunks, 2 trunks with 1 IRN perforating the SSL in 11%, 3 t runks with a IRN does not pierce SSL in the 9.5% and 12.3% in three trunk. The afferent way consists of sensory fibers of PN stimulated electrically at the dorsal nerve of the clitoris / penis.
It is essential to consider that the nerve is made up of many nerve fibers (NF). Increasing the intensity of stimu lation has the effect a gradual increase in the number of NF recruited (spatial summat ion). The receiver corresponds to a sensitive current-transducer number, fro m which the stimu lation intensity (I) is converted to a number (N) of activated NF[N = f (I)]. On a normal subject, the threshold intensity is the minimu m number of NF whose action potentials arriving phase have a resultant intensity sufficient to trigger the refle x.
But if on the afferent way the individual nervous conductions are desynchronized or if a denervation is important, the reflex is absent or requires a higher stimulat ion intensity.
In this case, D.
Vodusek [15] shown we can get the reflex with 2 or many coupled stimu lations. We get the same effect by recording the reflex during voluntary contraction force of the anal sphincter (personal method).
The afferent message will be articulated relat ing to a transfer module located at S2-S4 spinal cord with a system of interneurons. This message, via the transfer module, will excite the outflow tract at the start of the ventral horn o f the spinal cord (S2-S4) located in the nucleus of Onuf. All of the reflex arc takes about 35 ms (N <44 ms).
Muscle response can be recorded at all perineal pelvic muscles. c. 51 healthy subjects divided into 38 wo men and 13 men were selected. These subjects are free of pain pelvic-perineal and / or functional sign pelvic-perineal and / o r pelvic viscera of ptosis. Carriers of blemishes that may be associated with neuropathy were eliminated fro m the study.
The 13 men were investigated for evaluation before treatment by finasteride (9 for alopecia and 4 for benign prostatic hyperplasia). 38 wo men were investigated for stress incontinence by cervico-urethral hypermobility (staged sacral reflexes made before the urodynamic investigations) Patient age is between 26 and 83 years, with an average of 58 years.
d. 134 patients, included 83 wo men and 51 men suffering fro m pudendal neuralgia with a positive response to the infiltrat ion of truncal PN.

Methods
a. Location of the pubococcygeus muscle ( fig. 3)  •Pubococcygeus muscle (Q3) (PCM ) fro m the dorsal quadrant: information on nerve conduction of the PN at the IPA. Subtracting the value of SR obtained at the dorsal quadrant to that obtained at the pubococcygeus muscle. If the IRN forward pass of SSL, the value obtained will be similar (not significant) than that obtained on the dorsal quadrant.

Results
By studying the values obtained on the sacral reflexes on pelvic floor muscles with the study exp lored the d ifferences recorded between each of these muscles in all healthy subjects and patients with pudendal neuralg ia (Table 1), detailing the wo men (Table 2 ) and men (Table 3), we defined the min imu m and maximu m nervous time conduction between the quadrant ventral Q1 and dorsal quadrant Q2 and between Q2 and pubococcygeus muscle Q3 of 51 healthy subjects (table 4) and the 134 patients with pudendal neuralgia (table 5)    We were able to define maximu m normative values between these muscles (Table 6) provide guidance and topographic compressive (Table 7).
In the particular case of a conflict purely root S2, S3 or S4 kind Tarlov cyst, it will most often neurogenic signals without focal slowing of nervous conductions.
Legend: SR > N: the SR are h igher than normal on all the muscles explored, with no significant difference in terms of Q1, Q2 and Q3 SR <> N: The SR is higher or lower than normal but in all cases with significant differences between Q1 and Q2 and / or Q2 and Q3.

Discussion
a. Advantage of the differential staged sacral reflexes: • Reproducible method • Allow to exp lore the PN, fro m the sacral spine to the distal part via the sacral roots.
• A llo w to act out a TC at the IPA, can not be accessed with the PNTM L • Directs the head injury (sacral spine, IPA, IRF) • Few false positives • No false negatives b. Disadvantages: Appears to have 7.8% false positives. Note that 80% of these false positives have shown clinical signs of PN contralateral side to evoke electrophysiological within 2 years that follo wed exp loration EM G.
Study conducted on unilateral 64 pudendal neuralgia. 5 false positive contralateral side. 4 pudendal neuralg ia have their b ilateralized in two years that have followed. Can thus be estimated at 1.6% real rate of false positives.

Conclusions
Co mpared to the motor latency of the pudendal nerve (PNTM L), the differential staged sacral reflexes can, reproducibly, explore the whole pathway of the pudendal nerve and sacral spine. A PN entrap ment compression located in the infrapiriformis area (70-80% of cases) may be evoked, which is technically impossible with the PNTM L.