(Poster 175) Sacral Neuromodulation (SNM) Lead Sensing: An Objective Approach to SNM

Objectives: Responses to electrical nerve stimulation in sacral neuromodulation (SNM) are currently assessed using visual observation of anal bellows and/or toe thresholds and patient reported feedback (sensory threshold, ST). The Pelvic health Electrically Evoked Recording (PEER) 2 clinical study characterized sacral evoked responses (SERs) measured directly from the SNM lead as objective measures of sacral nerve activation.

Methods: SERs were collected from implanted, market-released SNM leads [Medtronic] using an external investigational research system in female subjects with overactive bladder undergoing a staged, tined-lead evaluation. Recordings yielded stimulation amplitudes associated with the first detectable signal (SER threshold, SERT). SERTs, motor thresholds, and STs were collected intraoperatively (OR), postoperatively immediately after lead placement (PO), and at end of therapy evaluation (Trial End).

Results: Recordings from sacral leads were collected in 90 subjects for at least one timepoint (OR/PO/Trial End). SERTs were reliably detected across subjects at each timepoint (OR: 100% (89/89 subjects); PO 98.9% (87/88 subjects); Trial End: 100% (88/88 subjects)). SERTs are relevant measures of sacral nerve activation exhibiting significant (p < 0.001) correlation to conventional measures across electrode configurations (OR bellows: R=0.44-0.72, n=86 subjects; OR toe: R=0.56-0.69, n=85 subjects; PO sensory R=0.69-0.91, n=87 subjects; Trial End sensory R=0.50-0.92, n=88 subjects). SERTs are a sensitive measure of sacral nerve activation, often detectable at or below STs (57-88% of subjects at Trial End by electrode configuration; Figure 1). SERTs are a consistent measure of sacral nerve activation; in a subset of 29 subjects, STs and SERTs were collected across four repeat measurements (single electrode configuration per subject at Trial End). Replicate SERT measures showed significantly less variation compared to STs (Figure 2). SERTs were the same across repeated measures in 48.3% of subjects, compared to 17.2% of subjects with no change in ST. Seven subjects reported adverse events related to the commercial device, commercial procedure, or commercial therapy, with none during investigational device use.

Conclusions: These data support potential advantages of lead-recorded SERTs as consistent and reliable measures of sacral nerve activation to enable objective therapy programming for SNM.

Disclaimer: CAUTION: Investigational device. Limited by Federal (U.S.) law to investigational use. Not approved by FDA and not for sale.

Figure 1: Sacral evoked response thresholds (SERTs) are a sensitive measure of sacral nerve activation. SERTs were detected at or below sensory threshold in 64-88% of subjects across electrode configurations. (E0=distal electrode, E3=proximal; P1-P4 = commercial external neurostimulator program [Medtronic])

Figure 2: Sacral evoked response thresholds (SERTs) are a more consistent measurement of sacral nerve activation compared to sensory threshold (ST). The patient-specific range was significantly lower for SERTs compared with STs across subjects (median [IQR]: SERT: 0.1[0.1] mA vs. ST: 0.2[0.2] mA; p < 0.001, Wilcoxon Signed Rank).