Hypothesis / aims of study
Sacral neuromodulation (SNM) is an effective approach for treating lower urinary tract dysfunction (LUTD), and stimulation programming is the key to successful treatment. However, little attention has been paid to SNM programming for the various indications. Thus, we aimed to confirm whether there are differences in the stimulation parameters for the indications of SNM and appropriate programming recommendations.
Study design, materials and methods
Clinical data were retrospectively collected from LUTD patients who underwent SNM and completed internal pulse generator (IPG) implantation. The parameters with the highest patient satisfaction or the most obvious symptom improvement during the test period were regarded as the optimal stimulation parameters and were used to set the programming after IPG implantation.
Results
After screening, 282 patients were enrolled and categorized into 4 groups based on different indications, namely, refractory overactive bladder (OAB) (n=61), neurogenic lower urinary tract dysfunction (nLUTD) (n=162), interstitial cystitis/painful bladder syndrome(IC/BPS) (n=24), and idiopathic non-obstructive urinary retention(NOUR) (n=35). When analyzing the optimal stimulus parameters, disparities in stimulation amplitude and pulse frequency were noted among the four groups. The stimulation amplitude in the nLUTD group was higher than that in the idiopathic NOUR group (P=0.013). Differences in pulse frequency were observed between the refractory OAB and nLUTD groups (P<0.001) and between the refractory OAB and idiopathic NOUR groups (P=0.001). Additionally, there were no differences in the electrode configuration or pulse width settings among the four groups.
Interpretation of results
The study analyzed the changes in the optimal stimulation parameters among the four groups compared to the standard stimulation parameters during initial programming. In terms of stimulation amplitude, only a small proportion of patients with refractory OAB, IC/BPS, and NOUR exceeded 2V (16%, 12%, and 6%, respectively), whereas more than one-third (37%) of the nLUTD patients exceeded above 2V. In terms of pulse frequency, patients in the nLUTD (60%) and NOUR (66%) groups tend to prefer frequencies higher than 14 Hz compared to the other groups. The majority of patients in the four groups ultimately tended to maintain the standard pulse width of 210μs (84%, 72%, 58%, 74%).
Concluding message
The optimal stimulation parameters for SNM vary between indications. From the initial programming, in terms of setting the stimulation amplitude, most patients strive to use subsensory stimulation and maintain it below 2V, whereas patients with nLUTD appropriately increase the stimulation amplitude, even surpassing 2V. For pulse frequency settings, patients with nLUTD and idiopathic NOUR may start at 26 Hz; however, it is not advisable to exceed 50 Hz, whereas other patients should aim to use the standard frequency (14 Hz) whenever possible. For all patients, it's recommended to use the standard pulse width (210μs), and adjusting pulse width is not advised as a primary focus of programming.