Disposable vaginal surface electrode for urethral sphincter electromyography

During the last 2 years we have developed a disposable vaginal surface electrode for electromyographic (EMG) recording from the urethral striated sphincter. We describe the design of the electrode and report the results of laboratory testing, including directional selectivity of the electrode, electrode impedance, testing for movement artefacts and stability of position. Clinical studies which included 138 cystometries with sphincter EMG, 133 pressure-flow EMG studies and four urethral pressure profile studies with sphincter EMG, demonstrated that the electrode gave technically good and reliable electromyographic data. The registration caused no discomfort to the patient and did not disturb the act of micturition. We recommend this technique for the evaluation of urethral striated muscle activity during urodynamic studies in women, since it is simple, inexpensive and reliable.     

Surface electrodes in perineal electromyography

In 40 elderly male patients undergoing multiple urodynamic evaluations, surface electrodes were used for recording electromyographic (EMG) activity of pelvic sphincter muscles; placement site was the external anal sphincter. The measured wave form was displayed as an analog plot. Different types of surface electrodes were evaluated in selected patients. The EMG wave form measurements varied with the type of surface electrode used and placement of the electrode. Surface electrodes for external anal sphincter EMG resulting in optimum signal response require a small metallic recording surface with an adhesive that will secure the electrode to the skin, proper anatomic placement of the electrode, appropriate preparation of the skin surface at the site of application of the electrode, and capabilities for oscilloscope monitoring of the sphincter EMG signal wave form. If properly used, surface electrodes result in a signal amplitude and frequency that approach the quality of concentric needle electrodes.     

A disposable anal plug electrode for pelvic floor/anal sphincter electromyography

During the last year we developed a disposable anal plug electrode for pelvic floor/external anal sphincter electromyography. The electrode consists of 2 disposable silver chloride surface electrodes mounted on a trochlear-shaped sponge. Testing of the new electrode with simultaneous registration of external anal sphincter electromyography using a coaxial needle electrode showed synchronous electromyographic patterns. In clinical urodynamic studies, including 48 cystometry studies with anal sphincter electromyography and 48 pressure-flow electromyographic studies, the electrode provided technically good and reliable electromyograms. The electrode design secures good contact to the recording surface and a safe fixation of the electrode during recording. The compressibility of the electrode might circumvent the problem of possible detrusor reflex inhibition induced by conventional hard anal plug electrodes. We recommend this technique for anal sphincter electromyography, since it is simple, reliable and without discomfort, and it does not require sterilization of the electrode.     

Motor evoked potentials from the striated urethral sphincter: a comparison of concentric needle and surface electrodes

AIMS: The aim of this study is to compare two different surface electrodes (intravaginal and intraurethral) with the concentric needle as a criterion standard and concomitant testing of the levator ani as a potential contaminator. METHODS: Thirty healthy women with a mean age of 52 years. Bland-Altman plots were used to compare recorded latencies from the various electrodes and muscles. RESULTS: There was no significant difference between the latencies recorded with the various electrodes from either muscle, but the limits of agreement were wide. However, the concentric needle electrodes proved more reliable with a higher rate of reproducible responses. CONCLUSIONS: We did not encounter major difficulties in using the concentric needle electrode for recordings in the external urethral sphincter, and this electrode was also more reliable than either surface electrode. Therefore, we advocate the use of concentric needle electrodes in future studies.     

Improved method for needle electromyography of the urethral sphincter in women

Needle electromyography (EMG) of the urethral sphincter using the periurethral approach is a procedure which most women find painful and their discomfort can restrict the use fulness of the test. A new technique has been devised using a transvaginal approach. The patient lies in the left lateral position and using a Sims speculum the posterior vaginal wall is retracted. The urethral sphincter can be easily seen and palpated, assisting correct electrode placement. This new technique is much less uncomfortable and highly satisfactory EMG recordings are obtained. © 1994 Wiley-Liss, Inc.     

Concentric needle electrodes are superior to perineal surface-patch electrodes for electromyographic documentation of urethral sphincter relaxation during voiding

OBJECTIVE: To compare interpretations of electromyographic (EMG) recordings from perineal surface patch electrodes (PSPEs) to those from urethral concentric needle electrodes (CNEs) during voiding. PATIENTS AND METHODS: Consenting women underwent urodynamic testing with a 30 G, 3.8 cm CNE at the 12 o'clock position in the striated urethral sphincter muscle, and with PSPEs placed at the 2 and 10 o'clock positions around the anus. Pressure-flow studies were conducted with simultaneous input from both EMG electrodes. Representative, de-identified paper copies of EMG signals were assembled by chronology and electrode type. Six examiners unaware of the patient details were asked to determine if the tracings were interpretable and whether there was quiescence of the urethral sphincter motor unit during voiding. The agreement between the interpretations of each tracing was assessed using McNemar and kappa statistics. RESULTS: Twenty-two women undergoing urodynamic testing for incontinence (16), voiding dysfunction (two) or urinary retention (four) participated in this study. CNE tracings were consistently more interpretable than PSPE tracings (mean 89% vs 67%). When tracings were interpretable, a significantly higher percentage of CNE EMG tracings (mean 79%) had urethral sphincter motor unit quiescence than PSPE EMG tracings (mean 28%). The kappa values for agreement among the reviewers' interpretations were highly variable and none were statistically significant. Reviewers unanimously agreed on only 12 of the 44 tracings, and 11 of these showed quiescence when using a CNE. CONCLUSIONS: CNEs are more often interpretable than PSPEs for determining motor unit quiescence during voiding. CNE EMG appears to have greater clinical utility for central reading than PSPEs.     

Urethral sphincter EMG activity registered with surface electrodes in the vagina

Transvaginal registration of urethral sphincter EMG with surface electodes at the anterior vaginal wall has been compared to simultaneous registrations of urethral ring electrode EMG and anal surface electrode EMG in 12 patients. We found that the transvaginal EMG was almost identical to the intraurethral EMG during different pelvic floor muscle activities but differed considerably from the perianal EMG. The clinical applicability was investigated during medium-fill water cystometry followed by pressure-flow studies, and in 21 out of 25 patients, a satisfactory EMG was registered.     

A new approach to electromyography of the external urethral sphincter

Detailed electromyographic investigation of the external urethral sphincter was done as part of a urodynamic evaluation of 119 patients. The sphincter was located by inserting electrodes alongside the urethra. The electromyogram was viewed on an oscilloscope and recorded on paper. Normal and abnormal sphincter electromyograms were defined and the role of sphincter electromyography in urodynamic studies was discussed. It was observed that electromyographic activity does not always correlate with urethral resistance but must be interpreted in conjunction with other urodynamic parameters, such as urethral pressures, urinary flow rates and voiding cystourethrography. In addition, sphincter electromyography provides valuable information to define the various neural pathways involved in micturition and continence.     

Pediatric urodynamics: a clinical comparison of surface versus needle pelvic floor/external sphincter electromyography.

Urodynamic evaluations were done on 37 children to diagnose voiding pattern abnormalities and/or recurrent urinary infections. Each of 25 children had 2 sets of testing to judge a practical method of urodynamic evaluation. Bipolar anal skin electrodes were compared to bipolar perianal muscle needle electrodes as a means of monitoring the urethral sphincter/pelvic floow electromyographic activity. In addition, the urethral catheter was compared to the suprapubic catheter as a means of monitoring intravesical pressure. The results were similar and statistically significant (p less than 0.001). The remaining 12 children were evaluated based only on the results of bipolar anal skin electrodes and uroflowmetry. The results of both groups clearly demonstrated that surface perianal electrodes are practical, accurate and reliable for the diagnosis and treatment of children with voiding pattern abnormalities. We recommend the use of surface electrodes and a urethral catheter as techniques for the urodynamic evaluation of voiding pattern abnormalities of children without overt neuropathology or extensive urethral operation. Preoperative surface electromyography of the urinary sphincters may prove to be a useful screening test to detect occult dyssynergia in patients who have had failed ureteral reimplants.     

A comparative study of various electrodes in electromyography of the striated urethral and anal sphincter in children

The series comprised 41 children aged 6 to 14 years consecutively referred with recurrent urinary tract infection and/or enuresis. Carbon dioxide cystometry was carried out in the supine and the erect position and combined with simultaneous electromyography (EMG). The external urethral sphincter was examined with a ring electrode mounted on a urethral catheter, while recordings from the striated anal sphincter were based on an anal plug electrode and perianal electrocardiographic (ECG) skin electrodes: 211 EMG and cystometric examinations were performed and all three methods gave satisfactory results. Correlation between them was good, as was reproducibility. Perianal surface ECG electrodes are recommended for the evaluation of functional disturbances of the external sphincter. They are painless, easy to use, and are well tolerated by the patient.     

Urethral sphincter needle electromyography in women: Comparison of periurethral and transvaginal approaches

Needle electromyography (EMG) of the striated urethral sphincter is the only technique that permits detection of individual motor unit action potentials (MUAPs) and is a valuable diagnostic tool in the evaluation of women with urinary incontinence and voiding disorders. The purpose of this study was to compare two methods of urethral needle EMG with respect to the number of MUAPs identified, the amount of patient discomfort, and the duration of the examination. Twenty consecutive women referred for electrodiagnostic testing to evaluate symptoms of urinary incontinence and/or voiding dysfunction underwent both methods of the needle examination in a prospective randomized cross-over study design with each patient acting as her own control. A full cross-over analysis was conducted to detect period and sequence effects using analysis of variance with a power of 0.85 and a significance level of P < 0.05. Twice as many MUAPs were identified using the periurethral approach (8.8 versus 3.9) with a mean difference of 5.0 (P = 0.0008). There was a non-significant trend to greater patient discomfort with the periurethral approach; however, the discomfort was generally rated as mild to moderate. The length of time required to count all identifiable MUAPs did not vary significantly between the two methods. We conclude that the periurethral approach is superior to the transvaginal approach with respect to the quantity of electrodiagnostic information obtained and propose that this method be standardized to characterize more accurately the neurogenic component of urinary incontinence and voiding dysfunction for future electrodiagnostic studies. Neurourol. Urodynam. 17:531–535, 1998. © 1998 Wiley-Liss, Inc.     

Maximum urethral closure pressure and sphincter volume in women with urinary retention

PURPOSE: In 1988 a syndrome of isolated urinary retention in young women that is associated with electromyographic abnormality of the striated urethral sphincter was described. It was hypothesised that urinary retention resulted from a failure of sphincter relaxation. The electromyographic abnormality causes overactivity of the muscle and may induce changes of work hypertrophy. If the hypothesis that the electromyographic abnormality is the cause of urinary retention is correct, we would expect the urethral sphincter to be enlarged and the urethral pressure profile to be increased in these women. We evaluated the role of static urethral pressure profilometry and transvaginal ultrasound in women in urinary retention. MATERIALS AND METHODS: A total of 66 women in complete or partial urinary retention underwent electromyography of the striated urethral sphincter using a concentric needle electrode, followed by urethral pressure profile and/or urethral sphincter volume measurement by transvaginal ultrasound. RESULTS: Maximum urethral closure pressure plus or minus standard deviation was significantly increased in patients with versus without the electromyographic abnormality (103 +/- 26.4 versus 76.7 +/- 18.4 cm. water, p <0.001). Maximum urethral sphincter volume was also increased in women with versus without the abnormality (2.29 +/- 0.64 versus 1.62 +/- 0.32 cm.3, p <0.001). CONCLUSIONS: The results of this study are consistent with the hypothesis that a local sphincter abnormality is the cause of urinary retention in a subgroup of women. Urethral pressure profilometry and sphincter volume measurement are useful for assessing these cases, especially when sphincter electromyography is not readily available.     

Diagnostic discordance of electromyography (EMG) versus voiding cystourethrogram (VCUG) for detrusor-external sphincter dyssynergy (DESD)

AIMS: Detrusor sphincter dyssynergia (DSD) is defined as: "a detrusor contraction concurrent with an involuntary contraction of the urethral and/or periurethral striated muscle." In neurogenic etiology, this usually refers to involuntary contraction of the external striated sphincter and has classically been termed detrusor-external sphincter dyssynergia (DESD). There is currently no consensus regarding diagnosis [specifics of electromyographic (EMG) or voiding cystourethrographic (VCUG) determination], and little data on how well these modalities correlate. We explore the diagnostic congruence for DESD between needle EMG and VCUG in the neurogenic population. METHODS: Consecutive studies performed by a single urodynamicist at a major neurologic center were reviewed. Presence of DESD was determined by increased wire needle EMG activity and/or by dilated bladder neck and proximal urethra during detrusor contraction, in the absence of valsalva or attempt to inhibit voiding. Minimal acceptable criterion for agreement between the two tests was set at 70%. RESULTS: Fourty nine patients were diagnosed with DESD, had a videourodynamic study available, and had no history of sphincterotomy or stent. Binomial testing demonstrated significant disagreement (P < 0.000) in observed proportions. There was 60% agreement (28 patients) and 40% disagreement (21 patients) between EMG and VCUG for diagnosis of DESD. CONCLUSIONS: We found significant disagreement between needle EMG and VCUG for a positive diagnosis of DESD. A combination of EMG and VCUG may identify more cases of DESD than either modality alone and underscores the need for more strict criteria when defining this entity from a urodynamic standpoint.     

Use of anal sphincter electromyography during operations on the conus medullaris and sacral nerve roots.

The mechanical activity of the anal sphincter can be translated into electrical activity and recorded on graph paper or an oscilloscope. The activity of the anal sphincter may be extrapolated to activity of the external urethral sphincter because both are striated muscles innervated by the pudendal nerve that arises from S-2, S-3, and S-4. Stimulation of these nerves causes contraction of the sphincter muscles, and a deflection of the recording device occurs. This technique was employed intraoperatively in monitoring operations on the conus medullaris and sacral nerve roots in 10 patients with spinal dysraphism (age range, 3 weeks to 15 years). Their diagnoses were tethered conus, 4; lipomeningocele, 3; spinal hamartoma, 1; syringocele, 1; and sacral arachnoiditis, 1. With general anesthesia, and the patient in the prone position, an electrode-containing anal plug was inserted or two needle electrodes were inserted into the anal sphincter muscle. The electrodes were connected to the electromyography recording stylus of the urodynamic bladder diagnostic unit. During the spinal operation, whenever a structure could not be identified clearly, it was stimulated with the disposable electrical stimulator and, if oscillations of the stylus occurred (indicating contraction of the anal sphincter), the structure was preserved. This technique permitted spinal operations in these 10 patients without changes in neurological or urological function.     

The relationship between external anal and external urethral sphincter activity in continent women

The relationship between the external anal sphincter and the periurethral sphincter muscles is an unresolved issue. Recordings of the external anal sphincter (EAS) are commonly used to indicate the responses of the urethral sphincter during urodynamic evaluations and in biofeedback procedures for the treatment of urinary incontinence. This study examined the validity of using anal sphincter training to teach control of the external urethral sphincter. Subjects were 5 continent women, aged 37–51 years, who reported being free of all urologic symptoms. Using visual biofeedback of anal sphincter pressure, subjects were trained to voluntarily contract the sphincter to four amplitudes: 5, 10, 15, and 20 mmHg (6.8, 13.6, 20.4, and 27.2 cmH₂O). Then they were guided through a series of controlled anal sphincter contractions, while the response of the urethral sphincter was measured using surface electrodes embedded in a Foley catheter. At each of four bladder volumes, subjects performed 16 contractions (four contractions at each of the four amplitudes). The order of contractions was counterbalanced, using a Latin square design. The results show a strong, statistically significant, monotonic relationship between the magnitude of anal sphincter contraction (pressure) and the level of urethral sphincter electromyographic (EMG) activity. The results support the use of the external anal sphincter as an indicator of urethral sphincter activity for the purpose of conducting biofeedback in the treatment of urinary incontinence.     

Quantitative evaluation of electrodes for external urethral sphincter electromyography during bladder-to-urethral guarding reflex

Purpose  

Accuracy in the recording of external urethral sphincter (EUS) electromyography (EMG) is an important goal in the quantitative evaluation of urethral function. The aim of this study was to quantitatively compare electrode recordings taken during tonic activity and leak point pressure (LPP) testing.     

Sacral evoked potentials in normal women and in women with stress incontinence

Recently, using electromyographic techniques, Swash, Snooks, and Henry [1985] and Smith and Warrel [1985] described disorders of perineal floor innervation in patients with foecal incontinence and stress urinary incontinence. Another means to determine the integrity of pelvic floor innervation is the measurement of the bulbo-cavernosus reflex latency. We performed sacral evoked potentials (SEP) in women, recording the EMG response by surface electrodes at the level of the anal sphincter. With this method, we studied 28 normal women and 31 with stress incontinence. Orienting the electrodes at the anal level always in the same faction (the active electrode on the right side), we obtained, in every case, a constant shape of SEP. This can help in doubtful cases. There was a statistical difference of SEP latencies in the two groups of women (32.9 msec and 38.92 msec, respectively). We concluded that in women with stress incontinence, there is an impairment of the pelvic floor innervation.     

Abnormal electromyographic activity (decelerating burst and complex repetitive discharges) in the striated muscle of the urethral sphincter in 5 women with persisting urinary retention

In five women with urinary retention, recordings from the striated muscle of the urethral sphincter revealed highly abnormal electromyographic (EMG) activity. Using a concentric needle electrode, recordings revealed very striking bursts of activity, referred to here as decelerating burst (DB) and complex repetitive discharges (CRD). Such EMG activity is exceedingly unusual in skeletal striated muscle and resembles most closely the rarely encountered condition of "pseudomyotonia". We suggest that this abnormal activity is associated with a failure of relaxation of the striated muscle of the urethral sphincter, which results in chronic retention.     

Refractoriness of urethral striated sphincter during voiding: studies with afferent pudendal reflex arc stimulation in male subjects

To assess the excitability of the striated sphincter under normal and abnormal conditions, electrostimulation of the periurethral striated sphincter via the dorsal nerve of the penis was done with the patient at rest and during voiding. Monitoring of simultaneous intravesical and intramembranous urethral pressures, and electromyographic responses of the striated sphincter was performed under fluoroscopic guidance in 14 male subjects. The urethral striated sphincter attained a state of relative refractoriness during detrusor contraction (voiding phase) and greater amounts of afferent stimulation were required to elicit sphincter contractile activity compared to the amounts required during resting states. Under conditions of a hyperactive detrusor with synergic voiding, the amounts of stimulation required to elicit striated sphincter responses were higher than those required in normal subjects. On the other hand, under conditions of striated sphincter dyssynergia, minute amounts of afferent stimulation were enough to produce sphincter contraction during voiding.     

On-line quantitative analysis of surface electromyography of the pelvic floor in patients with faecal incontinence

BACKGROUND: Needle electromyography (EMG) remains the 'gold standard' for the assessment of external anal sphincter innervation. It is, however, an invasive and poorly tolerated technique. In this study a quantitative form of surface electromyography was compared with needle EMG of the external anal sphincter. METHODS: Invasive needle EMG to assess mean fibre density and neuromuscular jitter was compared directly with quantitative surface EMG in 37 patients with faecal incontinence and 12 age-matched controls. RESULTS: There was a significant positive correlation between mean fibre density on needle EMG and maximum turns rate on surface EMG (rs = 0.48 (95 per cent confidence interval 0.28-0.76), P = 0.003). Furthermore, surface EMG was able to discriminate between patients with normal neuromuscular jitter and those with increased jitter, a measure of progressive denervation and reinnervation, on the basis of reduced rectified mean surface signal (P = 0.02, Fisher's exact test). CONCLUSION: Quantitative surface EMG may potentially replace invasive needle EMG as the investigation of choice in the assessment of anal sphincter electrophysiology.