Perineal surface electromyography does not typically demonstrate expected relaxation during normal voiding

Abstract

Aims: To describe perineal surface patch electromyography (EMG) activity during urodynamics (UDS) and compare activity between filling and voiding phases and to assess for a relationship between preoperative EMG activity and postoperative voiding symptoms.

Methods: 655 women underwent standardized preoperative UDS that included perineal surface EMG prior to undergoing surgery for stress urinary incontinence. Pressure-flow studies were evaluated for abdominal straining and interrupted flow. Quantitative EMG values were extracted from 10 predetermined time-points and compared between fill and void. Qualitative EMG activity was assessed for the percent of time EMG was active during fill and void and for the average amplitude of EMG during fill compared to void. Postoperative voiding dysfunction was defined as surgical revision or catheterization more than 6 weeks after surgery. Fisher's exact test with a 5% two-sided significance level was used to assess differences in EMG activity and postoperative voiding dysfunction.

Results: 321 UDS had interpretable EMG studies, of which 131 (41%) had EMG values at all 10 predetermined and annotated time-points. Quantitative and qualitative EMG signals during flow were usually greater than during fill. The prevalence of postoperative voiding dysfunction in subjects with higher preoperative EMG activity during void was not significantly different. Results were similar in the 42 subjects who had neither abdominal straining during void nor interrupted flow.

Conclusions: Perineal surface patch EMG did not measure expected pelvic floor and urethral sphincter relaxation during voiding. Preoperative EMG did not predict patients at risk for postoperative voiding dysfunction.

Conflict of interest statement

Conflicts of interest: none.

Copyright © 2011 Wiley Periodicals, Inc.

Figures

Fig. 1

Median EMG values (in microvolts) at time-points during fill (first desire, strong desire, and MCC) and flow (uroflow start, Qmax, and uroflow stop) as well as CMG baseline, PFS baseline, and pre- and postvoid coughs. This graph demonstrates that EMG values were generally higher during flow than during fill. Black bars present median EMG values for all 131 subjects in which all 10 time-points were annotated, gray bars present median EMG values for the 42 of these subjects with neither straining nor interrupted flow. Error bars: 75th and 25th percentiles.