Paper 23: Evidence of Altered Neuromuscular Function in the Striated Urethral Sphincter of Women with Prior Continence Procedures

Abstract

OBJECTIVE: To compare urethral sphincter neuromuscular function in stress incontinent women with prior incontinence surgery (sling or Burch) to stress incontinent women without prior incontinence surgery. METHODS: Following IRB approval, urethral EMG data for 13 women with prior sling and urodynamic stress incontinence (USI) and 13 women with prior Burch and USI were compared to 39 women with USI without prior incontinence surgery (controls). Cases were matched to controls (1:3) on age (within 10 years) and parity (0 or ≥1). Urethral EMG signals were obtained as part of the preoperative clinical urodynamic assessment. The EMG signal was assessed quantitatively after correct concentric needle placement using an automated software program on a Nicolet Viking IVp electrodiagnostic instrument. EMG data was obtained at with the subjects at rest (baseline), with cough, and with maximal squeeze. The quantitative mean rectified voltages (MRV) were compared in cases vs. controls. RESULTS: Study participants had a median age of 55 years (range 31–74) and parity of 3 children. Fifty-eight percent of participants had USI with concomitant detrusor overactivity, while the remaining 42% had pure USI. Forty percent had stage II prolapse, 18% had stage 0 or I, 16% stage III and 8% stage IV. Women with a prior sling had significantly lower quantitative EMG values with cough, while baseline and squeeze values were not different. Women with a prior Burch had cough EMG values intermediate between the control and prior sling group, which trended toward significance (P=0.057) CONCLUSION: Stress incontinent women with prior slings have poorer urethral sphincter neuromuscular function than age and parity matched stress incontinent women without prior incontinence surgery. This data may help explain the mechanism of reduced surgical success rates with subsequent continence procedures. This difference is not seen at rest, suggesting the importance of a clinically relevant measure of sphincteric integrity.TABLE 1