Pelvic Floor Muscle Electromyography as a Guiding Tool During Lead Placement and (Re)Programming in Sacral Neuromodulation Patients: Validity, Reliability, and Feasibility of the Technique

Abstract

To assess the validity, reliability, and feasibility of electromyography (EMG) as a tool to measure pelvic floor muscle (PFM) contractions during placement and (re)programming of the tined lead electrodes in sacral neuromodulation (SNM) patients. Single tertiary center, prospective study conducted between 2017 and 2019 consisting of three protocols including a total of 75 patients with overactive bladder (wet/dry) or nonobstructive urinary retention. PFM EMG was recorded using the multiple array probe (MAPLe), placed intravaginally. All stimulations (monophasic pulsed square wave, 210 μsec, 14 Hz) were performed using Medtronic's standard SNM stimulation equipment. During lead implantation, all four lead electrodes were stimulated with fixed increasing stimulation intensities (1-2-3-5-7-10 V). During lead electrode (re)programming, five bipolar lead electrode configurations were stimulated twice up to when an electrical PFM motor response (EPFMR), sensory response, and pain response were noted (i.e., the threshold), respectively. Additionally, amplitude and latency of the EPFMRs were determined. Validity, reliability, and feasibility were statistically analyzed using the intraclass correlation coefficient, weighted Cohen's kappa and linear regression, respectively. Validity: EPFMRs were strongly associated with visually detected PFM motor responses (κ = 0.90). Reliability: EPFMR amplitude (ICC = 0.99) and latency (ICC = 0.93) showed excellent repeatability. Feasibility: linear regression (EPFMR threshold = 0.18 mA + 0.76 * sensory response threshold) showed an increase in the sensory response threshold is associated with a smaller increase in EPFMR threshold, with the EPFMR occurring before or on the sensory response threshold in 83.8% of all stimulations. Measuring PFM contractions with EMG during placement and (re)programming of lead electrodes in SNM patients is valid, reliable, and feasible. Therefore, the use of PFM EMG motor responses could be considered as a tool to assist in these procedures.