Denervation and re-innervation of the urethral sphincter in the aetiology of genuine stress incontinence: an electromyographic study

Abstract

Objective: To investigate the role of altered innervation of the urethral sphincter in the genesis of genuine stress incontinence.

Design: Prospective observational study.

Setting: Tertiary referral centre urodynamics unit.

Subjects: Sixty-eight women, 33 with urodynamically proven pure genuine stress incontinence and 35 controls without urinary symptoms.

Interventions: Concentric needle electromyography of the urethral striated sphincter.

Main outcome measures: The means of motor unit potential duration, number of changes in polarity and the amplitude of individual motor unit potentials were compared between the two groups.

Results: There was no statistically significant difference in motor unit potential duration (P = 0.87) or in the number of changes in polarity (P = 0.85). There was a trend towards a higher amplitude of motor unit potentials in the control group (P = 0.07).

Conclusions: Our findings suggest that denervation and re-innervation of the striated urethral sphincter following trauma to the pelvic floor, such as that occurring during childbirth, is not a major aetiological factor in the development of genuine stress incontinence.