Quantitative anal sphincter electromyography in primiparous women with anal incontinence

Current developments in surface electromyography

Background/aim

Surface electromyography (surface EMG) is a primary technique to detect the electrical activities of muscles through surface electrodes. In recent years, surface EMG applications have grown from conventional fields into new fields. However, there is a gap between the progress in the research of surface EMG and its clinical acceptance, characterized by the translational knowledge and skills in the widespread use of surface EMG among the clinician community. To reduce this gap, it is necessary to translate the updated surface EMG applications and technological advances into clinical research. Therefore, we aimed to present a perspective on recent developments in the application of surface EMG and signal processing methods.

Materials and methods

We conducted this scoping review following the Joanna Briggs Institute (JBI) method. We conducted a general search of PubMed and Web of Science to identify key search terms. Following the search, we uploaded selected articles into Rayyan and removed duplicates. After prescreening 133 titles and abstracts, we assessed 91 full texts according to the inclusion criteria.

Results

We concluded that surface EMG has made innovative technological progress and has research potential for routine clinical applications and a wide range of applications, such as neurophysiology, sports and art performances, biofeedback, physical therapy and rehabilitation, assessment of physical exercises, muscle strength, fatigue, posture and postural control, movement analysis, muscle coordination, motor synergies, modelling, and more. Novel methods have been applied for surface EMG signals in terms of time domain, frequency domain, time-frequency domain, statistical methods, and nonlinear methods.

Conclusion

Translating innovations in surface EMG and signal analysis methods into routine clinical applications can be a helpful tool with a growing and valuable role in muscle activation measurement in clinical practices. Thus, researchers must build many more interfaces that give opportunities for continuing education and research with more contemporary techniques and devices.

Effects of delivery mode and age on motor unit properties of the external anal sphincter in women

INTRODUCTION AND HYPOTHESIS

This study aimed to assess the individual and interactive effects of delivery mode and age on the function of the external anal sphincter (EAS) by analyzing the motor unit properties with intramuscular electromyography (EMG). Results are expected to improve the understanding of delivery-related occult obstetric EAS injuries and its development over the aging process and further support early clinical detection and intervention.

METHODS

A total of 49 postpartum women were recruited into four test groups according to their age and delivery mode: young vaginal delivery (Y-VD), elderly vaginal delivery (E-VD), young cesarean section (Y-CS), and elderly cesarean section (E-CS) groups. Anorectal ultrasonography, manometry, and intramuscular EMG were employed for comprehensive evaluation of EAS function.

RESULTS

No significant difference in anorectal ultrasonography and most manometry measurements was associated with delivery age or mode. Intramuscular EMG, however, revealed a statistically significant difference in the characteristics of motor unit potentials (MUPs), including duration, turns, phases, and multiphase wave ratio between four subject groups. No significant interaction effect between age and delivery mode was found.

CONCLUSIONS

Delivery mode and age have a significant effect on the neuromuscular function of the EAS, suggesting a potential protectiveness of cesarean section against impairment to the EAS. Our results do not provide significant evidence regarding the interaction effect of delivery mode and age; further investigations are needed to confirm this conclusion.

Obstetric risk factors for early-onset anal incontinence

PURPOSE

The aim of the study was to identify primiparous pregnant women with a higher risk for early anal incontinence (AI) after labour.

METHODS

In the retrospective case control study, 133 primiparous women were questioned using the Wexner scoring system, and possible obstetric anal sphincter injuries (OASIS) were assessed using endoanal ultrasonography (EUS) 6-12 weeks after the labour. Obstetric characteristics (possible risk factors) for AI were collected from the maternal medical records. The univariate and multiple regression of maternal, neonatal and labour risk factors were calculated. Cut-off values were set to divide women into groups with higher and lower risk for AI.

RESULTS

The data of 30 primiparous women with and 103 without AI were analysed. Univariate logistic regression of obstetrics characteristics showed that stimulation of labour (RO [95% CI] 3.31 [1.07, 10.28]) and neonatal head circumference (RO [95% CI] 1.36 [1.03, 1.78]) are both associated with AI. With a neonatal head circumference of 34 cm or more (cut-off value), probability for AI was 33%, while below that value, it was just 2%. The incidence of AI was not significantly different between women with surgically repaired OASIS and women without anal sphincter injury.

CONCLUSION

The findings can assist in the identification of pregnant women at higher risk of AI. The women at higher risk of AI should be given special attention during the labour and specific rehabilitation after the labour.

Effect of vaginal delivery on the external anal sphincter muscle innervation pattern evaluated by multichannel surface EMG: results of the multicentre study TASI-2

INTRODUCTION AND HYPOTHESIS

A correlation exists between external anal sphincter (EAS) damage during birth and the subsequent development of fecal incontinence. This study evaluated the effect of delivery-related trauma on EAS innervation by means of intra-anal EMG performed with a rectal probe with 16 silver electrodes equally spaced along the circumference, before and after delivery.

METHODS

Pre-partum EMG measurements were performed on 511 women, by nine clinical partners from five European countries at the 28th to 34th gestational weeks and the 6th to 8th post-delivery weeks; 331 women returned, after delivery, for the second test. The innervation zones (IZ) of EAS single motor units were identified by means of an EMG decomposition algorithm.

RESULTS

The subjects were divided into four groups according to the delivery mode (Caesarean, vaginal with no evident damage, spontaneous lacerations and episiotomies). The number of IZs before and after delivery was compared. In the 82 women who underwent right mediolateral episiotomy, a statistically significant reduction of IZs was observed, after delivery, in the right ventral quadrant of the EAS (side of the episiotomy). Women who had Caesarean section, spontaneous lacerations or lack of evident damage did not present any significant change in the innervation pattern.

CONCLUSIONS

Right episiotomy reduces the number of IZs on the right-ventral side of the EAS. The fast and reliable test proposed indicates the sphincter innervation pattern before delivery and helps obstetricians to evaluate the risks and to choose the preferred side of the episiotomy, if deemed necessary at the time of delivery.

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.

Complete rupture of anal sphincter in primiparas: long-term effects and subsequent delivery

OBJECTIVE

To study long-term effects with respect to anal incontinence, pain, attitude to and mode of second delivery following complete rupture of the anal sphincter.

DESIGN

Case-control study. Settings. Södersjukhuset, a university hospital in Stockholm.

POPULATION

A case group of 136 primiparas who had experienced a complete rupture of the anal sphincter. Two matched control groups of primiparas, one of whom had cesarean section and the other a normal vaginal delivery.

METHODS

The case women were examined and asked for symptoms of anal incontinence 3-6 months after delivery; 3-8 years later they and two matched control groups answered a postal questionnaire. Response rate was 89%.

MAIN OUTCOME MEASURES

Symptoms of pelvic floor dysfunction and, as secondary end-point, the attitude to and mode of second delivery.

RESULTS

Anal incontinence after delivery was reported by 31% in the case group, and at long-term follow-up by 54% in the case group, 21% in the cesarean section and 23% in the normal delivery group (p < 0.0001). A wish to postpone or abandon further childbirth was significantly more common in the case women (33 and 18%) than in the other groups, but about 60% delivered again in all groups. In the case group, the next delivery was by cesarean section in 49%.

CONCLUSION

At long-term follow-up after a complete rupture of the anal sphincter, anal incontinence was common and many women wished to postpone or avoid further delivery.

Concentric Needle Quantitative EMG of Pubovisceralis Muscle Group: Normative Data from Asymptomatic Nulliparous Women

OBJECTIVES: The muscles of the pelvic floor closest to the vaginal opening are subject to the greatest degree of stretch during vaginal childbirth. We aim to define normative quantitative EMG (QEMG) parameters for the pubovisceralis (PV) muscle in nulliparous women, and compare them to the external anal sphincter (EAS). METHODS: In 31 asymptomatic nulliparous women, concentric Needle EMG of the PV and the EAS was performed. Multi-motor unit action potential (Multi-MUAP) and interference pattern (IP) algorithms were utilized to obtain QEMG parameters. We used paired t-tests to compare PV and EAS parameters. RESULTS: The motor units for the PV were of greater duration (p < 0.002) and had more turns (p = 0.03) than the paired motor units in the EAS. The EAS demonstrated more turns/second (p = 0.02), greater activity (p = 0.01), and more short segments (p = 0.009) than the PV. CONCLUSIONS: The PV has longer and more complex motor units than the EAS. This knowledge continues to improve our ability to detect neuropathic changes in this vulnerable muscle area following childbirth or in women with pelvic floor dysfunction. In addition, the PV muscle group appears less responsive to requests for increased neuromuscular activity than the EAS. This needs to be further evaluated, as it may be associated with understanding which portion of the muscle functionally shortens to maintain the closure of the levator hiatus.

Gastrointestinal motility testing

Gastrointestinal motility and the effects on luminal contents that are brought about by it can be studied in several ways. In clinical practice, manometry remains one of the most important investigational techniques, in particular for oesophageal and anorectal disorders. Radiographic examination of bolus transit through the gastrointestinal tract also continues to be a valuable tool. Scintigraphy still is the gold standard for assessment of gastric emptying, but (13)(C) breath tests are an alternative. Many other techniques are used mainly in the context of scientific research but some of these may become incorporated in the diagnostic armamentarium.