DENERVATION AND RE-INNERVATION OF THE URETHRAL SPHINCTER IN THE ETIOLOGY OF GENUINE STRESS-INCONTINENCE - AN ELECTROMYOGRAPHIC STUDY

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.