The Effect of Pulse Rate Changes on the Clinical Outcome of Sacral Neuromodulation

Purpose: We evaluated the effect of pulse rate changes on the clinical response to and stimulation related pain symptoms of sacral neuromodulation treatment. Materials and Methods: In this pilot study we evaluated the effect of 4 pulse rates, including 5.2, 10, 21 and 40 Hz, in patients with a suboptimal response to sacral neuromodulation. The effect of each frequency was evaluated during a 6-day test period. To avoid the carryover effect stimulation was discontinued for 24 hours between consecutive test periods. On the last 3 days of each test period a voiding diary and questionnaire were completed. Changes in the clinical response and pain symptoms were compared between the 4 pulse rates using multivariate analysis. Results: Of the 50 patients included in the study 40 (80%) were female. Mean +/- SD age was 55.5 +/- 12.3 years. Of the patients 41 (82%) had overactive bladder symptoms and 9 (18%) were in chronic nonobstructive urinary retention. No significant difference was found in clinical outcome on the voiding diary and questionnaire between the pulse rates and none of the 4 rates was significantly related to sacral neuromodulation associated pain. However, individuals appeared to benefit from changing the pulse rate in terms of treatment efficacy and stimulation related pain. Conclusions: On the group level none of the 4 pulse rates appeared to have a significantly different effect on clinical outcome or sacral neuromodulation related pain. However, an individualized approach to optimize treatment efficacy by changing the pulse rate appears to be useful.