Sacral neuromodulation (SNM) is a common treatment option for refractory overactive bladder, non-obstructive urinary retention, and fecal incontinence. We retrospectively evaluated patients who had undergone SNM lead placement with intraoperative electromyography (EMG) and compound muscle action potential responses (CMAP) during placement. Our objective was to determine how intraoperative EMG and CMAP affect programming and patient outcomes.

This is a single institution retrospective study of patients who have undergone placement of a Medtronic® SNM unit. Patients underwent either stage 1 and 2 placement or combined placement following an office peripheral nerve evaluation from January 2023 to March 2025. We identified patients who underwent lead placement with EMG monitoring with CMAP stimulation testing of the targeted S3 nerve root.  Intraoperative responses and program amplitudes for programs 1 through 4 were recorded. Intraoperative programs were compared to their SNM program data and outcome responses at first postoperative follow up.

Total of 70 individuals were included in the study. Patients, with mean age of 60.9 and average BMI of 29.6, were divided into 3 groups: participants whose program amplitudes (mA) at follow-up matched the intraoperative program mA during lead placement (12.9%), those whose follow-up mA was higher than the intraoperative program (45.7% higher at follow-up group), and those whose follow-up mA was lower than the intraoperative program (41.4% lower-at-follow-up group). Overall, symptom improvements were similar between the different groups. At follow-up, program or mA changes were made in 44.4%, 53.1% and 48.3% of the matched, higher-at-follow-up and lower-at-follow-up groups respectively. Of those requiring changes to enhance symptom improvement, the matched and higher-at-follow-up groups mainly changed program (75% and 94.1% respectively), while in the lower-at-follow-up group both program (57.1%) and mA changes (42.9%) were commonly implemented.

Performing EMG and CMAP during lead placement allows the medical team to record the minimal amplitudes needed to stimulate the sacral nerve. At follow-up, a significant number of patients presented with a mA setting that is lower than recorded intraoperatively, meaning their program is likely not (efficiently) stimulating the sacral nerve. In these cases, the right course of action would be to increase the mA to the intraoperative program setting, if tolerated by the patient. However, in more than half of these patients the program was changed rather than making adjustments to the amplitude. On the contrary, patients that presented with a matched or higher mA at follow-up would benefit from program change, which was indeed implemented in most cases.

Study indicates that there are no symptomatic outcome differences between patients with the same or different programing regarding their recorded intraoperative EMG and CMAP responses. However, there is a difference between the three groups regarding the program and amplitude changes implemented at their post operative follow up. Overall, an intraoperative CMAP defines the minimum mA to activate a nerve and can be used to decide whether to change amplitude or programs.

Continence 19S (2026) 102679
DOI: 10.1016/j.cont.2026.102679