Inferior Rectal Nerve Research Articles

Anatomic relationships of the pudendal nerve branches

We sought to characterize the distribution of the pudendal nerve branches and to correlate findings with injury risk related to common midurethral sling procedures. Dissections were performed in 18 female cadavers. Biopsies were obtained to confirm gross findings by histology. In all dissections, most of the clitoral and perineal nerves coursed caudal to the ventral portion of the perineal membrane. The inferior rectal nerve did not enter the pudendal canal in 44% (n = 8) of specimens. Nerve tissue was confirmed histologically in tissue sampled. The clitoral and perineal branches of the pudendal nerve should be at low risk of direct nerve injury during midurethral slings and similar procedures as they course caudal to the ventral portion of the perineal membrane. The inferior rectal nerve might be at risk of injury during procedures that involve passage of needles through the ischioanal fossa.

Effect of injury on S1 dorsal root ganglia in an experimental model of neuropathic faecal incontinence

An experimental model of neuropathic faecal incontinence has recently been established. This study aimed to quantify and compare the effect of crush and compression injury on first-order sensory neurones of the inferior rectal nerve (IRN) using a nuclear marker of axonal injury, activating transcription factor (ATF) 3. Eighteen Wistar rats were allocated to three groups: an unoperated control group, an IRN crush group (positive control) and a retrouterine balloon compression group. Five days after surgery, all animals were anaesthetized and perfused with fixative, and S1 dorsal root ganglia (DRG) were harvested. The tissue was sampled and neuronal nuclear ATF-3 expression calculated. Estimated total S1 DRG ATF-3 nuclear labelling was higher in the nerve crush (median (interquartile range) 171 (60-824) cells) and balloon compression (59 (20-274) cells) groups, compared with that in the unoperated control group (9 (3-24) cells) (P = 0.001 and P = 0.008 respectively). In all groups, most neurones displaying the marker of injury were of the C-fibre class. This study confirmed the presence of axonal injury in a pelvic compression model of obstetric injury. C-fibre afferent pathways appeared to be most vulnerable. Neuromodulation may function through augmentation of residual C-fibre pathways.

Anatomical Study of the Human Pudendal Nerve and its Application in Clinical Practice

Background: The pudendal nerve block is widely used in patients undergoing gyaenecologic, obstetric and penile surgery. But in some cases, the pudendal nerve block may fail and be ineffective. This may be due to failure of localization of the pudendal nerve or anatomical variations in its origin, course or branching pattern. Aim of the work was to study the anatomical variations of the pudendal nerve and the accurate localization of the pudendal nerve in relation to surface landmarks such as the ischial spine. Materials and Methods: This study was carried out on thirteen dissected human Egyptian pelves, gluteal regions and perineums (11 males and 2 females). Results: According to our examinations, the roots and trunks of the pudendal nerve could be grouped into four types: In Type I, the pudendal nerve arose from s3&4 in the form of one trunk (19.2%). This trunk divided into inferior rectal nerve, perineal nerve and dorsal nerve of the penis. In Type II, the pudendal nerve arose from s2,3&4 in the form of two trunks (34.6%). The medial trunk continued as the inferior rectal nerve, while the lateral trunk divided into perineal nerve and dorsal nerve of penis. In Type III, the pudendal nerve arose from s2&3 in the form of two trunks (15.5%). The lateral trunk got connected with the sciatic nerve, while the medial trunk divided into the perineal nerve and dorsal nerve of the penis. The inferior rectal nerve arose directly from the 3rd sacral nerve. In Type 1V, the pudendal nerve arose from s2&3 in the form of one trunk (30.8%). The origin of the inferior rectal nerve was variable. In 50%, it arose as a branch from the pudendal nerve after passing through the greater sciatic foramen. In 34.6%, the inferior rectal nerve was the continuation of the medial trunk of the pudendal nerve. In 15.4%, it arose directly from S3 and never joined the pudendal nerve. The dorsal nerve of the penis divided into two branches (medial and lateral) in 81.8% and three branches (medial, lateral and ventral) in18.2%. The medial branches of both sides communicated with each other to form a plexus behind the corona glandis to supply the glans. The ischial spine was an essential bony landmark for localization of the pudendal nerve. In the gluteal region, the point of the tip of the ischial spine represented the junction between the upper 2/3 and the lower 1/3 of a line extending between the posterior superior iliac spine and the ischial tuberosity. The point of crossing of the pudendal nerve to the sacrospinous ligament lay 1±0.5 cm medial to the point of the tip of the ischial spine. The surface line of the pudendal nerve divided equally the line extending between the base of the coccyx and the ischial tuberosity.

Anal nerve risks with paracoccygeal lumbosacral fixation

I commend your journal and authors Stefanski et al. [2] on the wonderfully educational research study titled, ‘‘The probability of finding nerve branches to the external anal sphincter’’. The authors’ assessment of 110 cadavers provided detailed analysis regarding nerve branches to the external anal sphincter. Since the time of the publication, there has been increasing interest in a relatively new surgical technique in this body region, specifically the paracoccygeal or transsacral approach to lumbosacral fixation surgery [1]. Based on the expertise that Stefanski et al. have in this region, it would be extremely interesting if they could comment on whether the paracoccygeal approach to lumbosacral fusion may place at risk the anal sphincter nerves that Stefanski studied. In this way, Stefanski’s anatomic expertise in this area might transcend directly into the clinical realm and shed some light (whether that be reassurance or warning) regarding the new, paracoccygeal surgical approach.

Sectional Neuroanatomy of the Pelvic Floor

This is the sixth in a series of articles on the spine. The first 5 reviewed the sectional anatomy of the cervical, thoracic, and lumbosacral spines. This paper will review both the male and female pelves. Procedures performed in the pelvis include electromyography of the anal sphincter, pudendal and sacral nerve stimulator implants, and botulinum toxin type A injections into the prostate, the bladder, the urethra, and the anus. Complications from these procedures are rare. Electromyography in this region is particularly uncomfortable. Botulinum toxin type A denervation may result in local effects such as incontinence or urinary retention or rarely remote effects such as limb weakness. Neurostimulators may get infected or may fail. This article provides anatomically accurate schematics of innervations of the pelvis that can be used to interpret magnetic resonance images of muscles and nerves in the pelvic floor region. Cross-sectional schematics of the male and female pelves were drawn as they appear on imaging projections. The relevant nerves were color coded. The muscles and the skin surfaces were labeled and assigned the color of the appropriate nerves. An organized comprehensive map of the motor innervation of both the male and female pelves allows the physician to increase the accuracy and efficacy of interventional procedures. This anatomic map could also assist the electromyographer in correlating the clinical and electrophysiologic findings on magnetic resonance images.

Central Representation of the Inferior Rectal Nerve of the Rat

Obstetric injury to the pudendal nerve contributes significantly to fecal incontinence. The inferior rectal nerve, a terminal branch of the motor division of the pudendal nerve, innervates the external anal sphincter. Animal models have been developed to establish the scientific basis of sacral neuromodulation. The aims of this study were to determine the spinal location of inferior rectal nerve motoneurons projecting to the external anal sphincter and whether the inferior rectal nerve carries sensory fibers. Ten female virgin Wistar rats were used; 7 underwent bilateral inferior rectal nerve section and application of the neuronal tracer fluorogold. Five days later dorsal root ganglia L5 to S2 and the lumbosacral spinal cord were harvested and stained for activating transcription factor 3, a molecular marker of nerve injury. Three animals were used to confirm the specificity of activating transcription factor 3 nuclear labeling as a marker of axotomy. Fluorogold-labeled motoneurons were found exclusively at L6 in the dorsomedial sections of Onuf's nuclei (left and right), which contained 30 +/- 9 motoneurons with a median diameter of 28.3 microm (24.4-31.0) (25th-75th centiles). Double-labeled sensory neurons (fluorogold-labeled cytoplasm and activating transcription factor 3-labeled nuclei) were found in dorsal root ganglia L6 to S2 and were smaller in diameter (20.5 microm (17.8-26.7); median (25th-75th centiles)) than motoneurons (P < .0,001). The external anal sphincter receives both motor and sensory innervation from the inferior rectal nerve. Activating transcription factor 3 nuclear staining may prove useful for quantifying the degree of nerve injury in animal models of fecal incontinence.

Reduced Somatosensory Cortical Activation in Experimental Models of Neuropathic Fecal Incontinence

Alteration in cortical awareness may be the underlying abnormality in patients with neuropathic fecal incontinence. The cortical effects of inferior rectal nerve injury were determined using somatosensory evoked cortical potential recordings in an experimental model of neuropathic fecal incontinence. Eighteen female virgin Wistar rats were assigned equally to one of three groups: an unoperated control group, a nerve crush group (positive control), and a nerve balloon compression group. Four weeks following the injury, all animals underwent somatosensory evoked cortical potential recordings. Following this, the inferior rectal nerve was harvested, resin-embedded, sectioned (1 microm thickness), and axonal counts and axonal cross-sectional areas were analyzed using Scion Image software. Somatosensory evoked cortical potentials were reduced in the nerve crush and balloon compression groups compared with controls (P = 0.024, P = 0.03, respectively). The inferior rectal nerve was harvested in 14 of the 18 animals (4 control, 5 nerve crush, 5 balloon compression). There were no differences in median inferior rectal nerve total axonal counts (P = 0.69) or in the frequency distribution of axonal cross-sectional area between groups (control vs. nerve crush and control vs. balloon compression: P = 0.92, P = 0.17, respectively). Somatosensory evoked cortical potential amplitude is reduced following crush or compression injury to the inferior rectal nerve. In neuropathic fecal incontinence, alteration in cortical awareness may be the result of processing modification at a central and not peripheral level.

The course and branching pattern of pudendal nerve in fetus

The pudendal nerve is a considerably large branch of the sacral plexus. There are many articles in the literature concerning the pudendal nerve in adults, but as far as we know, there is none on the branching pattern and variations in pudendal nerve anatomy in fetus. This study investigates the pudendal nerve trunking with respect to the piriformis muscle in 25 formalin-fixed fetuses (50 sides of pelves, 15 females, 10 males), ranging from 20 to 37 weeks of gestation. We investigate pudendal nerve trunking in four types: Type I-a is defined as single-trunk with the inferior rectal nerve branching proximal to the dorsal nerve of penis/clitoris (38%), Type I-b is also single-trunk with the dorsal nerve of penis/clitoris branching proximal to the inferior rectal nerve (24%), Type II is double-trunk with medial trunk as an inferior rectal nerve (34%), and Type III is triple-trunk (4%). We measured the average diameter of the main trunk of pudendal nerve in Type I-a and I-b groups to be 0.98 +/- 0.33 mm. We also measured the average length of the pudendal nerve trunks before the dorsal nerve of penis/clitoris branch to be 7.35 +/- 3.50 mm. There was no significant statistical difference in the average length, diameter, number of trunks, and pudendal nerve variations between male and female and also right and left sides of the pelves. This first and detailed fetal study of pudendal nerve trunking with respect to the piriformis muscle would be useful for educational anatomy dissections and anatomical landmark definitions for relevant clinical procedures.

Experimental Models of Neuropathic Fecal Incontinence: An Animal Model of Childbirth Injury to the Pudendal Nerve and External Anal Sphincter

Childbirth is the most common cause of fecal incontinence and damage to the pudendal nerve is a major component of childbirth injury. This study was designed to develop an acute animal model of injury to the innervation of the external anal sphincter. Forty-eight female virgin wistar rats were studied. Two models of neuropathic injury were developed. Bilateral inferior rectal nerve crush (Group A) acted as a positive control. Prolonged intrapelvic retrouterine balloon inflation (Group B) simulated the pelvic compressive forces of labor. Quantitative analysis of external anal sphincter muscle function was performed by using electromyography, external anal sphincter specific force production, and stereologic calculation of external anal sphincter mass. Injury in both groups caused significant atrophy of the external anal sphincter (P = 0.002, ANOVA) and electromyographic evidence of reinnervation at one week. Specific force (mN force per mg mass) was not altered. External anal sphincter muscle mass recovered after four weeks in Group B. Balloon dilation within the boney pelvis results in denervation of the external anal sphincter and offers an experimental model of the effects of childbirth on the continence mechanism in humans.

Anatomic variations of the pelvic floor nerves adjacent to the sacrospinous ligament: a female cadaver study

Our objective was to document variations in the topography of pelvic floor nerves (PFN) and describe a nerve-free zone adjacent to the sacrospinous ligament (SSL). Pelvic floor dissections were performed on 15 female cadavers. The course of the PFN was described in relation to the ischial spine (IS) and the SSL. The pudendal nerve (PN) passed medial to the IS and posterior to the SSL at a mean distance of 0.6 cm (SD = +/-0.4) in 80% of cadavers. In 40% of cadavers, an inferior rectal nerve (IRN) variant pierced the SSL at a distance of 1.9 cm (SD = +/-0.7) medial to the IS. The levator ani nerve (LAN), coursed over the superior surface of the SSL-coccygeus muscle complex at a mean distance of 2.5 cm (SD = +/-0.7) medial to the IS. Anatomic variations were found which challenge the classic description of PFN. A nerve-free zone is situated in the medial third of the SSL.

Morphological study of external anal sphincter motoneurons and motor nerve fibers

Morphological study of external anal sphincter motoneurons and motor nerve fibers

Innervation of the levator ani muscles: description of the nerve branches to the pubococcygeus, iliococcygeus, and puborectalis muscles

We described the innervation of the levator ani muscles (LAM) in human female cadavers. Detailed pelvic dissections of the pubococcygeus (PCM), iliococcygeus (ICM), and puborectalis muscles (PRM) were performed on 17 formaldehyde-fixed cadavers. The pudendal nerve and the sacral nerves entering the pelvis were traced thoroughly, and nerve branches innervating the LAM were documented. Histological analysis of nerve branches entering the LAM confirmed myelinated nerve tissue. LAM were innervated by the pudendal nerve branches, perineal nerve, and inferior rectal nerve (IRN) in 15 (88.2%) and 6 (35.3%) cadavers, respectively, and by the direct sacral nerves S3 and/or S4 in 12 cadavers (70.6%). A variant IRN, independent of the pudendal nerve, was found to innervate the LAM in seven (41.2%) cadavers. The PCM and the PRM were both primarily innervated by the pudendal nerve branches in 13 cadavers (76.5%) each. The ICM was primarily innervated by the direct sacral nerves S3 and/or S4 in 11 cadavers (64.7%).

Systematization of the vesical and uterovaginal efferences of the female inferior hypogastric plexus (pelvic): applications to pelvic surgery on women patients

To locate and describe the various efferences of the plexus in order to make it easier to avoid nerve lesions during pelvic surgery on women patients through a better anatomical knowledge of the inferior hypogastric plexus (IHP). We dissected 27 formalin embalmed female anatomical subjects, none of which bore any stigmata of subumbilical surgery. The dissection was always performed using the same technique: identification of the inferior hypogastric plexus, whose posterior superior angle follows on from the hypogastric nerve and whose top, which is anterior and inferior, is located exactly at the ureter's point of entry into the base of the parametrium, underneath the posterior layer of the broad ligament. The IHP is located at the level of the posterior floor of the pelvis, opposite to the sacral concavity. Its top, which is anterior inferior, is at the point of contact with the ureter at its entry into the posterior layer of the broad ligament. The uterovaginal, vesical and rectal efferences originate in the paracervix. Three efferent nerves branch, two of them from its top and the third from its inferior edge: (1) A vaginal nerve, medial to the ureter, follows the uterine artery and divides into two groups: anterior thin, heading for the vagina and the uterus; posterior, voluminous, heading in a superior rectal direction (=superior rectal nerve). (2) A vesical nerve, lateral to the ureter, divides into two groups, lateral and medial. (3) The inferior rectal nerve emerges from the inferior edge of the IHP, between the fourth sacral root and the ureter's point of entry into the base of the parametrium. The ureter is the crucial point of reference for the IHP and its efferences and acts as a real guide for identifying the anterior inferior angle or top of the IHP, the origin of the vaginal nerve, the level of the ureterovesical junction and the division of the vesical nerve into its two medial and lateral branches. Dissecting underneath and inside the ureter and the uterine artery involves a risk of lesion of the vaginal nerve and its uterovaginal branches. Further forward, between the intersection and the ureterovesical junction, dissecting and/or coagulating under the ureter involves a risk of lesions to the vesical nerve, which are likely to explain the phenomena of denervation of the anterior floor encountered after certain hysterectomies and/or surgical treatments of vesicoureteral reflux.

Physioanatomical relationship of the external anal sphincter to the bulbocavernosus muscle in the female

Both external anal sphincter (EAS) and bulbocavernosus muscle (BCM) have been shown anatomically and physiologically to constitute one muscle in males. We investigated the hypothesis that the EAS and BCM have similar anatomical pattern in females. The study consisted of cadaveric dissection, electromyographic recordings and inferior rectal nerve stimulation. Bulbocavernosus reflex action was performed in 16 healthy women before and after anesthetization of the EAS and BCM. The EAS extended forward across the perineal body and became continuous with the BCM in the labia majora. Glans clitoris (GC) or inferior rectal nerve stimulation effected synchronous EAS and BCM contractions with identical action potentials. GC stimulation while the EAS or BCM was anesthetized produced neither EAS nor BCM response. Similarly, stimulation of the anesthetized GC produced no EAS or BCM response. The BCM and EAS apparently constitute a single muscle, which seems to play dual and yet synchronous roles in fecal control and sexual response.

Diagnosis and therapy of rectal cancer

BACKGROUND: Rectal cancer poses a formidable challenge to surgical treatment due to a technically difficult access in the pelvis with close proximity to functionally important structures such as the anal sphincters and autonomic nerves, which coordinate urinary bladder and sexual functions. Management therefore aims both at maximising local cure rates and minimising functional consequences of treatment. METHODS: Review of the literature on interdisciplinary management of rectal cancer. RESULTS: This review focuses on current evidence regarding diagnosis and treatment of rectal cancer from a practical viewpoint for the surgeon. The important relationship between accurate local staging and tailored primary therapy including neoadjuvant (chemo)radiation strategies is discussed. Evolution of curative operations based on embryological knowledge including possibilities and current limitations of local treatment and minimal access surgery are detailed. A detailed step-by-step description of the surgical technique of rectal resection is presented. CONCLUSIONS: Modern diagnostic tools and better understanding of rectal cancer biology have led to important advances in treatment. Optimal surgery integrated in a multimodality treatment strategy remains central in our attempts to improve local cure rates and survival for patients with rectal cancer.

Neurophysiological testing in anorectal disorders

The neurophysiological techniques currently available to evaluate anorectal disorders include concentric needle electromyography (EMG) of the external anal sphincter, anal nerve terminal motor latency (TML) measurement in response to transrectal electrical stimulation or sacral magnetic stimulation, motor evoked potentials (MEPs) of the anal sphincter to transcranial magnetic cortical stimulation, cortical recording of somatosensory evoked potentials (SEPs) to anal nerve stimulation, quantification of electrical or thermal sensory thresholds (QSTs) within the anal canal, sacral anal reflex (SAR) latency measurement in response to pudendal nerve or perianal stimulation, and perianal recording of sympathetic skin responses (SSRs). In most cases, a comprehensive approach using several tests is helpful for diagnosis: needle EMG signs of sphincter denervation or prolonged TML give evidence for anal motor nerve lesion; SEP/QST or SSR abnormalities can suggest sensory or autonomic neuropathy; and in the absence of peripheral nerve disorder, MEPs, SEPs, SSRs, and SARs can assist in demonstrating and localizing spinal or supraspinal disease. Such techniques are complementary to other methods of investigation, such as pelvic floor imaging and anorectal manometry, to establish the diagnosis and guide therapeutic management of neurogenic anorectal disorders.

Electrophysiologic Anal Tests and Sacral Nerve Modulation

Electrophysiologic Anal Tests and Sacral Nerve Modulation

Anatomical study of the pudendal nerve adjacent to the sacrospinous ligament

The pudendal nerve (S3-S5) is a major branch of the sacral plexus. After branching from the sacral plexus, the pudendal nerve travels through three main regions: the gluteal region, the pudendal canal, and the perineum. In the gluteal region, the pudendal nerve lies posterior to the sacrospinous ligament. The relationship of the pudendal nerve to the sacrospinous ligament has important clinical ramifications, but there is a lack of literature examining the variations in pudendal nerve anatomy in the gluteal region. This study investigates the pudendal nerve trunking in relation to the sacrospinous ligament in 37 cadavers (73 sides of pelves) of 21 males and 16 females, ranging from 18-83 years of age. Pudendal nerve trunking could be grouped into five types: Type I is defined as one-trunked (41/73; 56.2%), Type II is two-trunked (8/73; 11%), Type III is two-trunked with one trunk as an inferior rectal nerve piercing through the sacrospinous ligament (8/73; 11%), Type IV is two-trunked with one as an inferior rectal nerve not piercing through the sacrospinous ligament (7/73; 9.5%), and Type V is three-trunked (9/73; 12.3%). In summary, 56.2% of pudendal nerves adjacent to the sacrospinous ligament were one-trunked, 31.5% were two-trunked and 12.3% were three-trunked. Fifteen inferior rectal nerves originated independently from the S4 root and never joined the main pudendal nerve. Eight of fifteen inferior rectal nerves pierced through the sacrospinous ligament, perhaps making it prone for entrapment. We measured the average diameter of the main trunk of the pudendal nerve to be 4.67 +/- 1.17 mm. We also measured the average length of the pudendal nerve trunks before terminal branching to be 25.14 +/- 10.29 mm. There was no significant statistical difference in the average length, average diameter, number of trunks, and pudendal nerve variations between male and female or right or left sides of the pelves. A detailed study of pudendal nerve trunking in relationship to the sacrospinous ligament would be useful for instruction in basic anatomy courses and in relevant clinical settings as well.

18 P Anal sphincter electromyography and pudendal nerve terminal motor latency in the evaluation of anorectal disorders

18 P Anal sphincter electromyography and pudendal nerve terminal motor latency in the evaluation of anorectal disorders

Respective value of pudendal nerve terminal motor latency and anal sphincter electromyography in neurogenic fecal incontinence

Fecal incontinence may be related to a neurogenic injury. Electrodiagnostic tests including pudendal nerve terminal motor latency (PNTML) and external anal sphincter electromyography (AEMG) have been proposed to reveal anal nerve damage. The aim of this study was to assess the respective value of PNTML and AEMG in the diagnosis of fecal incontinence. This study included 80 women (range 23–85 years) with fecal incontinence secondary to obstetrical and/or surgical trauma. They were evaluated by performing PNTML and AEMG. The electrophysiological results were compared and interpreted in the light of anorectal manometry (ARM) results. Electrodiagnostic test abnormalities were found in 64 of 80 patients (80%), including 28 patients with abnormal results for both tests and 36 patients with only one abnormal test. Overall, a neurogenic AEMG pattern was found in 64% of patients and a prolonged PNTML in 51%. No correlation was found between PNTML value and either AEMG grade or ARM parameters, while AEMG grade strongly correlated with squeeze pressure measured by ARM. This study showed that AEMG and PNTML did not give redundant information and allowed to explicit the mechanisms of neurogenic fecal incontinence. We found that AEMG was more sensitive and more closely related to the anal functional status (ARM parameters) than PNTML. These electrodiagnostic tests, particularly AEMG as performed in everyday practice, are useful in the assessment of neurogenic fecal incontinence.