Onset of Action of Sacral Neuromodulation in Lower Urinary Tract Dysfunction: What is the Optimal Duration of Test Stimulation?

Purpose: Since the development of sacral neuromodulation, a large number of patients with lower urinary tract symptoms have been treated with this procedure. A test stimulation is performed prior to implantation. At centers worldwide the duration of this test stimulation varies considerably since it is not certain when the onset of the therapy effect can be expected. The objective of this prospective study was to evaluate the average onset time of sacral neuromodulation in patients with lower urinary tract symptoms. Materials and Methods: All patients who were eligible for treatment with sacral neuromodulation were asked to participate in this study. A voiding diary was filled out prior to and during test stimulation using an implanted tined lead. Success was defined as a 50% or greater improvement compared to baseline in any of the main complaint parameters. The Mann-Whitney U test was used to compare the mean time to success between patients with overactive bladder syndrome and patients with nonobstructive urinary retention. Results: Of the 45 patients 24 with nonobstructive urinary retention and 21 with overactive bladder syndrome agreed to participate and were included in study. Test stimulation was successful in 29 patients (64%). Mean time to success in all patients was 3.3 days (range 1 to 9). There was no significant difference in mean time to success between cases of overactive bladder syndrome and non obstructive urinary retention (3.25 and 3.5 days, respectively, p = 0.76). Conclusions: The results imply that a test stimulation of more than 2 weeks is not necessary if a cutoff of 50% or greater improvement is adopted. However, further improvement can be expected with prolonged test stimulation. This might be important since it might have implications for long-term results.