Sacral neuromodulation in women with idiopathic detrusor overactivity incontinence: decreased overactivity but unchanged bladder contraction strength and urethral resistance during voiding

PURPOSE: We evaluated the effect of sacral (S3) nerve neuromodulation on voiding in women with idiopathic detrusor overactivity incontinence. MATERIALS AND METHODS: Urodynamic measurements in all patients implanted in 1990 to 2003 were reconsidered. Patients were included if these measurements, which were done at baseline and after 6 months, could be analyzed completely and reliably. Maximum detrusor pressure, amplitude of the highest involuntary detrusor contraction and end fill volume were used as parameters characterizing the degree of detrusor overactivity. Urethral resistance and bladder contraction strength during voiding were characterized by the bladder outlet obstruction index, the urethral resistance factor, average pressure, the slope of the low pressure side of the pressure flow plot, the bladder contractility index and the bladder contraction strength parameter. RESULTS: A total of 33 women were included. Detrusor overactivity parameters were significantly improved at followup. In addition, the supine position of the patient during filling in followup measurements proved less provocative with respect to overactivity than the standing position in the majority of measurements at baseline. Consequently bladder volumes at which voiding was initiated were considerably higher at followup. Changes in the parameters characterizing urethral resistance and bladder contraction strength during voiding were not unambiguous. However, exactly those parameters that appeared volume independent in a previous study were not significantly different. CONCLUSIONS: Our study confirmed the depressant effect of sacral (S3) nerve neuromodulation on detrusor overactivity. No effect on urethral resistance and bladder contraction strength during voiding could be demonstrated using volume independent parameters

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