Pudendal nerve terminal motor latency: age effects and technical considerations

Advancing the predictive accuracy of PNTML in rectal prolapse: An ongoing quest

Fecal incontinence is a common symptom among patients with rectal prolapse. Pudendal nerve terminal motor latency (PNTML) testing can serve as a reference indicator for predicting the outcomes of rectal prolapse surgery, thereby assisting surgeons in formulating more appropriate surgical plans. The direct correlation between preoperative PNTML testing results and postoperative fecal incontinence in patients with rectal prolapse remains a contentious issue, necessitating further clarification. Thus, we analyze the existing publications from both clinical and statistical perspectives to comprehensively evaluate the accuracy of preoperative PNTML testing in rectal prolapse and provide some feasible statistical solutions.

Assessing Anorectal Function in Constipation and Fecal Incontinence

Constipation and fecal incontinence are commonly encountered complaints in the gastrointestinal clinic. Assessment of anorectal function includes comprehensive history, rectal examination, and prospective stool diary or electronic App diary that accurately captures bowel symptoms, evaluation of severity, and quality of life of measure. Evaluation of a suspected patient with dyssynergic constipation includes anorectal manometry, balloon expulsion test, and defecography. Investigation of a suspected patient with fecal incontinence includes high-resolution anorectal manometry; anal ultrasound or MRI; and neurophysiology tests, such as translumbosacral anorectal magnetic stimulation or pudendal nerve latency. This article provides an approach to the assessment of anorectal function.

The effect of sacral neuromodulation on pudendal nerve function and female sexual function

AIMS

To quantify changes in pudendal nerve function with sacral neuromodulation (SNM). To understand the relationship of pudendal nerve function to SNM treatment response for overactive bladder. To assess the relationship between female sexual function and pudendal nerve function after SNM.

METHODS

Women undergoing SNM between January 2010 and May 2011 were enrolled. Baseline pudendal nerve terminal motor latencies (PNTML) were measured bilaterally. Subjects underwent peripheral nerve evaluation (PNE) prior to SNM therapy. PNTML was measured at 1 and 6 weeks after sacral neuromodulator implant. Women who did not undergo permanent implantation were reassessed at the end of the 1-week PNE testing phase. Pelvic floor and sexual function questionnaires were administered at baseline and follow-up to assess pelvic floor and sexual function.

RESULTS

Of 34 women enrolled, 31 were evaluated. Mean age was 67.4 ± 14.2 years with 29/34 (85.3%) treated for refractory overactive bladder. Thirty of 31 (96.7%) went on to a permanent implant. PNE success rate was 73.5% (25/33). Mean PNTML changed from 2.74 ± 0.52 msec at baseline to 2.57 ± 0.50 msec at 6 weeks postop (P = 0.198). Baseline amplitude remained stable at 1 and 6 weeks. At 6 weeks PISQ-12 scores showed improved sexual function (P = 0.034) and PFDI-20 and PFIQ-7 scores showed improved pelvic floor, colorectal and urinary symptoms (P < 0.05).

CONCLUSIONS

Women with refractory overactive bladder and non-obstructive urinary retention have abnormal pudendal nerve function, which showed a non-significant trend toward improvement after SNM. Sexually active women undergoing sacral neuromodulation experienced improvement in sexual function. Quality of life improved due to improvement in urinary and colorectal function.

Factors affecting reflex pelvic floor muscle contraction patterns in women with pelvic floor disorders

OBJECTIVE

To explore factors affecting the presence of two reflex pelvic floor muscle contraction (PFMC) patterns in women with pelvic floor disorders.

METHODS

This was a retrospective analysis of pelvic floor ultrasonography and urodynamic data for 667 consecutive symptomatic women with pelvic floor disorders. We identified on ultrasonography the presence or absence of two reflex PFMC patterns, anorectal lift (ARL) and inward clitoral motion (ICM), preceding or occurring during coughing, and evaluated their associations with possible factors affecting reflex PFMC reactivity, including patient demographics, pelvic organ prolapse stages, ultrasonography findings and urodynamic data.

RESULTS

Of the 667 women, 560 (84.0%) clearly demonstrated reflex ARL and 536 (80.4%) demonstrated ICM. There were significant differences in age (P < 0.001), parity (P = 0.033) and menopausal status (P = 0.005) between women with and those without reflex ICM before or during coughing. The multivariable logistic regression model showed that age was the only independent factor associated with presence of reflex ICM (odds ratio, 0.93 (95% CI, 0.88-0.99), P = 0.017). In contrast, no significant differences were noted between women with and without reflex ARL.

CONCLUSIONS

Increasing age is negatively associated with the presence of reflex ICM during coughing in symptomatic women with pelvic floor disorders.

The effects of age and childbirth on anal sphincter function and morphology in 999 symptomatic female patients with colorectal dysfunction

BACKGROUND AND OBJECTIVES

Conflicting data exist on the contributions of advancing age and childbirth on the structure and function of the anal sphincter. This study aimed to examine the relative contributions of age and childbirth in a large cohort of women referred for investigation of symptoms of colorectal dysfunction (fecal incontinence and constipation).

SETTING

This study was conducted at a specialist surgical colorectal investigation unit in a university teaching hospital.

PATIENTS

Retrospective analysis was performed on prospectively collected demographic, symptom profile, and physiologic data from 3686 female patients. Strict exclusion criteria were applied, leaving 999 patients for univariate, multivariate, and logistic statistical modeling.

MAIN OUTCOME MEASURES

The effects of independent variables alone and in combination on anal sphincter pressures (resting and squeeze increment) and the presence of sphincter defects (internal and external) were expressed as regression coefficients and odds ratios.

RESULTS

Median age was 42 years (range, 16-88), and parity was 2 (range, 0-11); 16% were nulliparous. Three hundred sixty patients had fecal incontinence, 352 had constipation, and 287 had combined symptoms. Anal resting tone decreased with age by 0.66 cm H2O per year, and by 4.3 cm H2O per birth, and was associated with both internal and external anal sphincter defects (p = 0.0001 for both). Squeeze increment pressures decreased by 0.3 cm H2O per year, and by 3.8 cm H2O per birth; decreased pressures were, however, only significantly associated with external anal sphincter defects (p = 0.0001) as a result of childbirth. Cesarean delivery was protective against both reduced anal pressures and sphincter defects. Pudendal nerve terminal motor latencies increased bilaterally with age and with vaginal delivery; the impact of both was greater on the left nerve. Rectal sensation was unaffected by age or parity.

CONCLUSIONS

Aging predominantly affects anal resting pressures; childbirth, particularly instrumental delivery, is detrimental to the structure and function of the external sphincter.

Neurophysiology in neurourology

The bladder has only two essential functions. It stores and periodically empties liquid waste. Yet it is unique as a visceral organ, allowing integrated volitional and autonomous control of continence and voiding. Normal function tests the integrity of the nervous system at all levels, extending from the neuroepithelium of the bladder wall to the frontal cortex of the brain. Thus, dysfunction is common with impairment of either the central or peripheral nervous system. This monograph presents an overview of the neural control of the bladder as it is currently understood. A description of pertinent peripheral anatomy and neuroanatomy is provided, followed by an explanation of common neurophysiological tests of the lower urinary tract and associated structures, including both urodynamic and electrodiagnostic approaches. Clinical applications are included to illustrate the impact of nervous system dysfunction on the bladder and to provide indications for testing.

Manometric, sensorimotor, and neurophysiologic evaluation of anorectal function

With advances in diagnostic technology, it is now accepted that in the field of functional bowel disorders, symptom-based assessment is unsatisfactory as the sole means of directing therapy. A robust taxonomy based on underlying pathophysiology has been suggested, highlighting a crucial role for physiologic testing in clinical practice. A wide number of complementary investigations currently exist for the assessment of anorectal structure and function, some of which have a clinical impact in patients with functional disorders of evacuation and continence by markedly improving diagnostic yield and altering management. The techniques, limitations, measurements, and clinical use of manometric, sensorimotor, and neurophysiologic tests of anorectal function are presented.

Neurophysiology of the neurogenic lower urinary tract disorders

The nervous system structures involved in the control of the lower urinary tract (LUT) are usually divided using a neuroanatomical classification system into suprapontine, pontine, spinal and sacral. In all patients with LUT symptoms, after exclusion of local causes, a nervous system disorder needs to be considered. For the diagnosis of neurogenic LUT disorders, in addition to clinical assessment, neurophysiologic testing might be useful. Imaging and other laboratory studies (e.g., cystometry) often provide relevant additional information. Neurophysiologic tests are more useful in patients with sacral compared with suprasacral disorders. Although in patients with LUT disorders external urethral sphincter (EUS) electromyography (EMG) would seem the most appropriate, anal sphincter EMG is the single most useful diagnostic test, particularly for focal sacral lesions, and atypical parkinsonism. Another clinically useful method that tests the sacral segments, and complements EMG, is the sacral (penilo/clitoro-cavernosus) reflex. Kinesiologic EMG is useful to demonstrate detrusor sphincter dyssynergia (i.e., increased EUS activity during bladder contraction), which is particularly common in spinal cord disease. Somatosensory evoked potential (SEP) and motor evoked potential (MEP) studies (cortical and lumbar) may be useful to diagnose clinically silent central lesions. MEP, in addition, seems to be very promising in research into cortical excitability. Theoretically, cortical SEP on bladder/urethra stimulation would be much more useful than pudendal SEP because it tests thin nerve afferents from the pelvic viscera. However, the utility of this technique is limited by technical difficulties, which can be partially overcome by the concomitant recording of a palmar sympathetic skin response (SSR). SSR recorded from the saddle region is also useful for testing the lumbosacral sympathetic system. Although the technique of detrusor EMG has been recently described in humans, a clinically useful test for evaluating the sacral parasympathetic system, which is crucial for LUT functioning, is still lacking.

Pudendal nerve latency time in normal women via intravaginal stimulation

INTRODUCTION & OBJECTIVES

Studies of motor conduction for the efferent functional assessment of the pudendal nerve in women with pelvic dysfunctions have been conducted through researching distal motor latency times. The transrectal approach has been the classic approach for this electrophysiological examination. The objective of the present study is to verify the viability of the transvaginal approach in performing the exam, to establish normal values for this method and to analyze the influence of age, stature and parity in the latency value of normal women.

MATERIALS AND METHODS

A total of 23 volunteers without genitourinary pathologies participated in this study. In each, pudendal motor latency was investigated through the transvaginal approach, which was chosen due to patient's higher tolerance levels.

RESULTS

The motor response represented by registering the M-wave was obtained in all volunteers on the right side (100%) and in 13 volunteers on the left side (56.5%). The mean motor latency obtained in the right and left was respectively: 1.99 +/- 0.41 and 1.92 +/- 0.48 milliseconds (ms). There was no difference between the sides (p = 0.66). Latency did not correlate with age, stature or obstetric history. The results obtained in the present study were in agreement with those found by other researchers using the transrectal approach.

CONCLUSION

The vaginal approach represents an alternative for pudendal nerve distal motor latency time, with similar results to those achieved through the transrectal approach. Normative values obtained herein might serve as a comparative basis for subsequent physiopathological studies.

Fistula in ano surgery has no impact on pudendal nerve terminal motor latency

BACKGROUND

Anal fistula surgery is recognized as a major risk factor for anal incontinence. This incontinence is mainly due to surgical sphincter lesions, although a neurogenic mechanism through damage to the pudendal nerve is not excluded. The objective of our study was to evaluate the influence of anal surgery on the anal terminal motor latency of the pudendal nerve (PNTML).

MATERIALS AND METHODS

The PNTML values were measured pre- and postoperatively, respectively, in 33 patients (28 men, 5 women) treated for anal suppuration and 34 patients (21 men, 13 women) undergoing pedicular hemorrhoidectomy using the Milligan and Morgan technique.

RESULTS

The average age was 49.6 years in the hemorrhoid group and 45 years in the fistula group (p=0.19). There was no difference in the sex ratio between the two groups (p=0.06). In the anal fistula group, the preoperative mean PNTML was 2.42 (+/-0.46) ms on the infected side and 2.40 (+/-0.42) ms on the healthy side, with a significant difference from the control group's preoperative ipsilateral latencies: 2.73 (+/-0.60) ms (p=0.02, p=0.01). The variations in the postoperative PNTML of the fistula group, both on the healthy side (DeltaPNTML=0.06+/-0.42 ms) and on the diseased side (DeltaPNTML=0.03+/-0.40 ms), are comparable with those of the hemorrhoid group (DeltaPNTML=0.01+/-0.48 ms; p=0.63, p=0.84).

CONCLUSION

The nervous conduction of the pudendal nerves does not seem to be altered by the presence of an infectious process in the ischiorectal fossa nor by the surgical procedure. However, a more refined electrophysiological study would seem to be necessary to assess the repercussions on the perineal innervation.

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 studies and clinical findings in females with combined fecal and urinary incontinence: a prospective study

PURPOSE

Several clinical, urodynamic, and manometric findings suggest neurologic damage as a contributing factor in the development of combined fecal and urinary incontinence. In this study, we wanted to test the hypothesis of pudendal nerve neuropathy being a more frequent lesion in patients with double incontinence compared with patients with isolated fecal incontinence.

PATIENTS

Ninety-three females with combined fecal and urinary incontinence and 36 females with isolated fecal incontinence were investigated. All patients underwent anal manometry, endoanal ultrasound, electromyography, and pudendal nerve terminal motor latency.

RESULTS

No statistically significant differences were found in the age, history of vaginal delivery, and chronic straining between both groups. However, the rate of postmenopausal females was higher in the combined fecal and urinary incontinence group (85 vs. 67 percent; P = 0.02). Menopause was an independent risk factor of having double incontinence (odds ratio, 1.4; P = 0.02). Concentric needle electromyography of the external anal sphincter revealed increased duration of the motor unit potentials in 43 and 53 percent of patients with combined fecal and urinary incontinence and isolated fecal incontinence, respectively (P = 0.28). An increased number of polyphasic motor unit potentials was detected in 52 and 58 percent (P = 0.6). There was no statistically significant difference in the prevalence of bilateral (20 vs. 27 percent) or unilateral (23 vs. 14 percent) prolonged mean pudendal nerve terminal motor latency between both groups (P = 0.3).

CONCLUSIONS

Pudendal neuropathy is not a distinct characteristic of patients with double incontinence. The prevalence of pudendal neuropathy in these patients is similar to that observed in patients with isolated fecal incontinence. Others factors should be investigated to explain the common association of both types of incontinence.

External anal sphincter responses after S3 spinal root surface electrical stimulation

AIMS

The aim of this study is to present the normative data of direct and reflex motor anal sphincter responses, simultaneously evoked by S3 surface electrical stimulation. By this method, it is possible to test the functional integrity of the nervous pathways activated during sacral neuromodulation (SNM).

METHODS

Twenty healthy subjects were studied. Motor-evoked potentials (MEPs) were recorded by concentric needle electrode from external anal sphincter (EAS). Electrical stimulation was applied by means of a bipolar surface electrode over the S3 right or left sacral foramina.

RESULTS

Direct (R1) and reflex responses (R2 and R3) were found at latencies of 6.98, 25.12, and 50.31 msec, respectively. The two first responses were recorded in all the cases; the last response is steadily recorded in 17 out of 20 subjects.

CONCLUSIONS

Our data can serve as reference values for future study in patients with pelvic floor dysfunction. EAS responses following S3 percutaneous electrical stimulation can represent a useful aid in the selection of candidates to SNM.

Intrarectal ground electrode improves the reliability of motor evoked potentials recorded in the anal sphincter

Motor evoked potentials (MEPs) can be recorded in the external anal sphincter in response to magnetic stimulation of the cerebral cortex or sacral roots. However, the magnitude of the stimulus artifact may alter the reliability of anal MEP recording. An intrarectal ground electrode substantially reduces stimulus artifact and technical failure, improving MEP latency determination to sacral root stimulation in particular.

Excitability of the motor cortical representation of the external anal sphincter

This study was designed to assess the excitability of the motor cortical representation of the external anal sphincter by using transcranial magnetic stimulation (TMS). In six healthy volunteers, the rest motor threshold and the duration of the cortical silent period were determined with single TMS pulses, and the intracortical inhibition and facilitation were measured with paired TMS pulses. Values obtained from the anal sphincter were compared with those obtained from a muscle in the right hand. All subjects completed the study. Rest motor threshold and intracortical facilitation were similar in both muscles. In contrast, cortical silent period duration and intra-cortical inhibition were less for the anal sphincter than for hand muscle. This study has opened new perspectives for the investigation of anal sphincter cortical control in humans.

A review of sacral nerve stimulation for the treatment of faecal incontinence

Sacral nerve stimulation is an emerging surgical technique that uses chronic low-level electrical stimulation, applied to the nerves of the sacral plexus, to produce a clinically beneficial physiological effect on the lower bowel, pelvic floor and anal canal. Faecal incontinence is common, maximal conservative therapy may improve some patients but many require surgery. Results are variable and often unsatisfactory and further options are limited, the traditional end-point being the formation of a colostomy. Sacral nerve stimulation appears to be an alternative treatment that is successful, has low morbidity, is maintained in the medium term and associated with an improved quality of life. The technique has the advantage of a minimally invasive test procedure with high predictive value and the surgery is minor. The underlying mechanism of action although predominately neurological in nature remains to be determined. Precise patient selection is currently unclear however, results are superior to other techniques.

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.