Striated anal sphincter electromyography in idiopathic fecal incontinence

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.

Diagnosis and treatment of faecal incontinence: Consensus statement of the Italian Society of Colorectal Surgery and the Italian Association of Hospital Gastroenterologists

Faecal incontinence is a common and disturbing condition, which leads to impaired quality of life and huge social and economic costs. Although recent studies have identified novel diagnostic modalities and therapeutic options, the best diagnostic and therapeutic approach is not yet completely known and shared among experts in this field. The Italian Society of Colorectal Surgery and the Italian Association of Hospital Gastroenterologists selected a pool of experts to constitute a joint committee on the basis of their experience in treating pelvic floor disorders. The aim was to develop a position paper on the diagnostic and therapeutic aspects of faecal incontinence, to provide practical recommendations for a cost-effective diagnostic work-up and a tailored treatment strategy. The recommendations were defined and graded on the basis of levels of evidence in accordance with the criteria of the Oxford Centre for Evidence-Based Medicine, and were based on currently published scientific evidence. Each statement was drafted through constant communication and evaluation conducted both online and during face-to-face working meetings. A brief recommendation at the end of each paragraph allows clinicians to find concise responses to each diagnostic and therapeutic issue.

Value of evoked potential in study of functional bowel disorders

In recent years, the development of neurogastroenterology and the application of neurophysiologic examinations have gradually revealed the association of gastrointestinal activity with cortical activity through the efferent and afferent pathways. The state of nerve conduction pathway between the brain and gastrointestinal tract is closely related with specific functions of the anus and rectum. Scholars have put forward the "brain gut axis" and "brain gut interaction" theories to explain the bidirectional interaction between the gastrointestinal tract and central nervous system. Evoked potentials have an important role in the diagnosis and research of electrophysiological changes in various parts of the neural system, which provides practical information for the study of the brain-gut pathway, promotes the diagnosis and understanding of diseases related to the brain-gut axis abnormalities, and provides the basis for developing new treatment methods. In this paper, we summarize the roles of various evoked potential techniques in the study of functional bowel disorders.

Fecal continence revisited: the anal external sphincter continence reflex

BACKGROUND

None of the current theories on fecal incontinence can explain fecal continence adequately.

OBJECTIVE

This study aims to evaluate the mechanism controlling fecal continence.

DESIGN

Anal electrosensitivity, anorectal pressures, and rectal pressure volumetry tests were performed in 17 controls before and after superficial local anal anesthesia and in 6 controls before and after spinal anesthesia. The same tests were performed in 1 patient before and after injected local anal anesthesia and in 3 patients with spinal cord lesions at levels Th3 to L3.

RESULTS

After superficial local anal anesthesia, anal electrosensitivity decreased, but basal anal pressure remained unaltered. Squeeze pressure decreased and rectal filling sensation levels remained. Local anesthesia reduced anal pressure recorded in the distal anal canal during progressive rectal filling. This was also the case, albeit more explicit, after the local anal anesthetic was injected. After spinal anesthesia, the anal canal became insensitive to electric stimulation, but basal and squeeze pressure values decreased substantially, and the increase in anal pressure during the balloon-retaining test disappeared completely. In the patients with spinal cord lesions, the external sphincter could not be squeezed on command, but during the balloon-retaining test, the anal sphincter did squeeze autonomously at more than 300 mmHg.

LIMITATIONS

These were partially experimental measurements. The relevance of the found model in the daily clinical practice will have to be studied in a following study.

CONCLUSIONS

Our results support the hypothesis that the component of fecal continence mediated by contraction of the external sphincter depends on a anal external sphincter continence reflex without involving the brain. Presumably, the afferent receptors of this reflex are contact receptors located superficially in the mucosa or submucosa of the distal anal canal. A nonfunctioning anal external sphincter continence reflex would, therefore, result in fecal incontinence (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A116).

Anal sphincteric neurogenic injury in asymptomatic nulliparous women and fecal incontinence

While anal sphincter neurogenic injury documented by needle electromyography (EMG) has been implicated to cause fecal incontinence (FI), most studies have been uncontrolled. Normal values and the effects of age on anal sphincter motor unit potentials (MUP) are ill defined. The functional significance of anal sphincter neurogenic injury in FI is unclear. Anal pressures and EMG were assessed in 20 asymptomatic nulliparous women (age, 38 ± 5 yr; mean ± SE) and 20 women with FI (54 ± 3 yr). A computerized program quantified MUP duration and phases. These parameters and MUP recruitment were also semiquantitatively assessed by experienced electromyographers in real time. Increasing age was associated with longer and more polyphasic MUP in nulliparous women by quantitative analysis. A higher proportion of FI patients had prolonged (1 control, 7 patients, P = 0.04) and polyphasic MUP (2 controls, 9 patients, P = 0.03) at rest but not during squeeze. Semiquantitative analyses identified neurogenic or muscle injury in the anal sphincter (11 patients) and other lumbosacral muscles (4 patients). There was substantial agreement between quantitative and semiquantitative analyses (κ statistic 0.63 ± 95% CI: 0.32-0.96). Anal resting and squeeze pressures were lower (P ≤ 0.01) in FI than controls. Anal sphincter neurogenic or muscle injury assessed by needle EMG was associated (P = 0.01) with weaker squeeze pressures (83 ± 10 mmHg vs. 154 ± 30 mmHg) and explained 19% (P = 0.01) of the variation in squeeze pressure. Anal sphincter MUP are longer and more polyphasic in older than younger nulliparous women. Women with FI have more severe neurogenic or muscle anal sphincter injury, which is associated with lower squeeze pressures.

Changes in fatigability of the striated anal canal after childbirth

AIM

Anal manometry is an established assessment tool for patients with faecal incontinence. Fatigue rate index (FRI) has been shown to discriminate between symptomatic patients and controls. The aim of this study was to compare manometry and fatigability of the anal canal in nulliparous women before and after childbirth.

METHOD

An air-filled manometry device was used to record maximum resting and squeeze pressures, fatigue rate (recorded over 20 s) and FRI. Recordings were made before and after vaginal delivery.

RESULTS

Nineteen women were studied. Resting anal canal pressure was not significantly different before and after delivery (57.1 +/- 13.6 vs 51.1 +/- 11.9 cmH(2)O, P = 0.1). Squeeze pressure was significantly lower postpartum (106.5 +/- 43.6 vs 75.5 +/- 45.6 cmH(2)O, P < 0.001). Fatigue rate was significantly reduced postpartum (-129.5 +/- 74.7 vs-76.1 +/- 54.8 cmH(2)O/min, P = 0.001), but FRI was not significantly altered (1.23 +/- 1.49 vs 1.41 +/- 1.27 min, P = 0.09).

CONCLUSION

Maximal squeeze pressure and fatigue rate of the anal canal are significantly reduced after childbirth. Resting anal canal pressure and FRI are not significantly different.

Neurophysiological testing in anorectal disorders

Neurophysiological tests of anorectal function can provide useful information regarding the integrity of neuronal innervation, as well as neuromuscular function. This information can give insights regarding the pathophysiological mechanisms that lead to several disorders of anorectal function, particularly fecal incontinence, pelvic floor disorders and dyssynergic defecation. Currently, several tests are available for the neurophysiological evaluation of anorectal function. These tests are mostly performed on patients referred to tertiary care centers, either following negative evaluations or when there is lack of response to conventional therapy. Judicious use of these tests can reveal significant and new understanding of the underlying mechanism(s) that could pave the way for better management of these disorders. In addition, these techniques are complementary to other modalities of investigation, such as pelvic floor imaging. The most commonly performed neurophysiological tests, along with their indications and clinical utility are discussed. Several novel techniques are evolving that may reveal new information on brain-gut interactions.

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.

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.

Surgical treatment of constipation and fecal incontinence

Fecal incontinence is a disabling and distressing condition. Many patients are reluctant to discuss the condition with a physician. A thorough history, good physical examination, and detailed anorectal physiologic investigations can help in the therapeutic decision-making algorithm. Patients with isolated anterior sphincter defects are candidates for overlapping repair. In the presence of unilateral or bilateral pudendal neuropathy, the patient should be counseled preoperatively regarding a [table: see text] lower anticipation of success. If the injury occurred shortly before the planned surgery and neuropathy is present, it may be prudent to wait because neuropathy sometimes can resolve within 6 to 24 months of the injury. Pudendal nerve study may help determine surgical timing. An anterior sphincter defect combined with a rectovaginal fistula can be approached by overlapping sphincter repair and a concomitant transanal advancement flap. Patients who had undergone multiple such procedures may benefit from concomitant fecal diversion at the time of repeat sphincter repair. Patients with global or multifocal sphincter injury may be candidates for a neosphincter procedure. The stimulated graciloplasty and artificial bowel sphincter are reasonable options. In the absence of the availability of these techniques or because of financial constraints, consideration could be given to bilateral gluteoplasty or unilateral or bilateral nonstimulated graciloplasty. The postanal repair still serves a role in patients with isolated decreased resting pressures with or without neuropathy or external sphincter injury with minimal degrees of incontinence. Biofeedback and the Procon device may play a role in these patients. Lastly, fecal diversion must be considered as a means of improving the quality of life because the patient can participate in the activities of daily living without the fear of fecal incontinence.

Standardization of anal sphincter electromyography: normative data

OBJECTIVES

Electromyography (EMG) of the external anal sphincter (EAS) is important in the evaluation of conus/cauda lesions, the differential diagnosis of parkinsonism and anal incontinence. The aim of our study was to establish normative data in a sufficiently large group of healthy subjects, using a rigorously standardized examination technique.

METHODS

Sixty-four subjects (aged 19-83 years) without pelvic or neurological disorders were included. Motor unit potentials (MUPs)/interference pattern (IP) samples were obtained from the EAS using multi-MUP and turn/amplitude analyses, respectively. The effect of age, gender, parity, and constipation on MUP/IP parameters was studied. For MUP parameters the lower/upper limits for mean values, and 'outlier' limits, and for IP parameters normal 'clouds' were calculated.

RESULTS

From 112 muscles 15-30 MUPs were sampled. As no effect of evaluated factors on mean values could be demonstrated, common reference values were calculated. Lower/higher limits for mean values were: amplitude 148/661 microV, duration 3.2/7.8 ms, area 87/625 microVms, and number of phases 2. 3/3.7. 'Outlier' limits for individual MUPs were: amplitude 84/1315 microV, duration 1.6/13.8 ms, area 46/1222 microVms, number of phases 2/6. From 95 muscles 2706 IP samples were obtained.

CONCLUSIONS

The presented normative data should allow valid quantitative EMG of the EAS muscle in patients.

Neosphincters in the management of faecal incontinence

BACKGROUND

Surgical treatment of end-stage faecal incontinence has its origin in the early 1950s. Interest has been revived as a result of technical advances achieved in the recent past. The purpose of this article is to review the principles that underlie the use of skeletal muscle transposition around the anal canal and of electrical stimulation in the treatment of incontinence, and to explore new methods of treatment of this condition.

METHODS

A literature search was performed using Pubmed and Medline, employing keywords related to treatment of faecal incontinence by neosphincter reconstruction. Basic science and clinical aspects of neosphincter reconstruction were gathered from relevant texts, original articles and recently published abstracts.

RESULTS

The electrically stimulated gracilis neoanal sphincter seems to be the popular choice of biological neosphincter. It is more likely to produce higher resting anal canal pressures than the unstimulated neosphincter, and hence improved continence. However, electrostimulator failure may result in explantation in a proportion of patients. Impairment of evacuation is a functional setback in approximately one-third of patients with the gracilis neosphincter. Overall, improvement of continence may be expected in up to 90 per cent of patients according to some reports. By contrast, experience with the artificial neosphincter, which is less expensive, has been limited to a few tertiary centres across the world. Reported continence of stool is 100 per cent, and that of gas and stool 50 per cent, following implantation of the artificial sphincter. Both of the above operations have been associated with implant-related infection and impaired evacuation.

CONCLUSION

Neoanal sphincter operations are technically demanding, require a considerable learning experience and should be confined to specialist colorectal centres. Patients are likely to benefit from a plan that incorporates preoperative counselling and a selective approach.

Artificial bowel sphincter (ABS) for severe faecal incontinence: a clinical and manometric study

OBJECTIVE

As experience with artificial sphincters for severe faecal incontinence is still limited, the authors' aim was to report on the outcome following implantation of the ABS in their series.

PATIENTS AND METHODS

Eight women (mean age 56 years, range 48-64 years) with severe faecal incontinence refractory to conservative treatment underwent ABS implantation. This condition was idiopathic in six of the patients, due to trauma in one and due to malformation in the remaining one. The mean preoperative score for incontinence (AMS classification) was 96.2 (range 70-108). Two of the patients had rectal prolapse and three anterior colpocele.

RESULTS

Two patients had post-operative infection requiring implant removal. In the six other patients (mean follow up 10.5 months, range 4-23 months) the mean incontinence score was 19.4 (range 0-61). Continence to solid stools was achieved in all six patients, although one complained of occasional episodes of incontinence to liquid stools and another of episodes of soiling; none had intolerance to the device, which functioned satisfactorily.

CONCLUSION

Our findings indicate that the ABS implant is well tolerated and may be a valid option in the treatment of severe incontinence, even in the presence of complex pelvic disorders, although the risk of infection must always be borne in mind. Studies on larger series with longer follow ups are required to confirm these preliminary findings.

External anal sphincter atrophy on endoanal magnetic resonance imaging adversely affects continence after sphincteroplasty

BACKGROUND

There is still considerable debate about the value of preoperative anorectal physiological parameters in predicting the clinical outcome after sphincteroplasty. Recently it has been reported that atrophy of the external anal sphincter can be clearly shown with endoanal magnetic resonance imaging (MRI). The aims of this study were to investigate the prevalence of external anal sphincter atrophy in women with anterior sphincter defects due to obstetric injury and to determine the impact of external anal sphincter atrophy on the outcome of sphincteroplasty.

METHODS

In this prospective study, 20 consecutive women (median age 50 (range 28-75) years) with faecal incontinence due to obstetric trauma were assessed before operation with endoanal ultrasonography and endoanal MRI. The external anal sphincter was examined and evaluated for the presence of atrophy. The clinical outcome of sphincteroplasty was interpreted without knowledge of the magnetic resonance and ultrasonographic images.

RESULTS

In all patients anterior sphincter defects could be demonstrated with ultrasonography and MRI. External anal sphincter atrophy could only be demonstrated on MRI. Eight of 20 patients had external anal sphincter atrophy. Continence was restored in 13 patients. Outcome was significantly better in those without external anal sphincter atrophy (11 of 12 patients versus two of eight; P = 0.004).

CONCLUSION

External anal sphincter atrophy can only be visualized on endoanal MRI and affects continence after sphincteroplasty. Endoanal MRI is valuable in the preoperative assessment of patients with faecal incontinence. Presented to the American Society of Colon and Rectal Surgeons in Philadelphia, Pennsylvania, USA, June 1997

Fecal incontinence with normal anal canal pressures: where is the pitfall?

OBJECTIVE

One third of subjects who suffer from fecal incontinence are found to have values within the normal range when anal manometry is performed. For these patients, one hypothesis is that impaired rectal adaptation to distension may occur. The aim of our study was to analyze anorectal responses to rectal isobaric distension in this population.

METHODS

This was a prospective study conducted in 51 consecutive incontinent patients (45 female, six male) divided into two groups according to their functional anal state: absence (19 patients aged 55 +/- 6 yr) or presence of manometric anal weakness (32 patients aged 59 +/- 2 yr). The subjects were submitted to two randomized modes of rectal isobaric distension (tonic, phasic) with an electronic barostat. Anal pressures, perception, and volumes of the rectum were recorded at six different preselected pressures.

RESULTS

As compared with those having anal weakness, patients with no anal weakness retained higher mean pressures at both upper (36.9 +/- 2.2 vs 22.9 +/- 1.4 mm Hg; p = 0.01) and lower parts (41.0 +/- 2.0 vs 23.3 +/- 1.4 mm Hg; p = 0.002) of the anal canal, similar perception scores, but much lower rectal volumes (68.5 +/- 5.5 vs 121.8 +/- 7.0 ml; p = 0.008) in response to rectal isobaric distension.

CONCLUSION

A decrease in rectal adaptation could be involved in fecal leakage in patients with no anal manometric weakness.

AGA technical review on anorectal testing techniques

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. Following external review, the paper was approved by the committee on May 17, 1998.