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

A Prospective Feasibility Study to Differentiate Sacral Neuromodulation Lead Electrode Configurations Using Motor and Sensory Thresholds and Locations of Sensation

Background Accurate positioning and effective programming of sacral neuromodulation (SNM) relies upon the use of several acute stimulation measurements. While the clinical utility of these acute measurements including pelvic floor motor thresholds (PFMT), toe/leg motor thresholds (TMT), and sensory thresholds (ST), are widely accepted, their usefulness in quantitative research remains unclear. The purpose of this prospective study was to test these measurements and gauge their utility in future research. Methods Eight participants received Axonics SNM, 6 Medtronic Interstim II, and 2 Medtronic Micro SNM. PFMT was measured after implantation. ST and the location of sensation (LOS) were measured immediately postoperatively (PO), at pre-release from the surgery center (PR), and during a follow-up clinic visit (FU). Thresholds were compared across contact and time using linear mixed-effects models. Results Significant differences in PFMT were found across electrode configurations, with stimulation through proximal contacts exhibiting lower PFMT than distal configurations. ST displayed no significant differences across electrodes and showed minimal changes over time. LOS exhibited substantial variability across patients and periods. Conclusions Results suggest that PFMT were able to differentiate differences across electrode configurations that may be useful for future quantitative research. The lack of differences in ST and LOS across electrode configurations was interesting given the focus on these measurements clinically. Future testing is to confirm these limitations.

Sensing in Sacral Neuromodulation: A Feasibility Study in Subjects With Urinary Incontinence and Retention

OBJECTIVES

Sacral neuromodulation (SNM) therapy standard of care relies on visual-motor responses and patient-reported sensory responses in deciding optimized lead placement and programming. Automatic detection of stimulation responses could offer a simple, consistent indicator for optimizing SNM. The purpose of this study was to measure and characterize sacral evoked responses (SERs) resulting from sacral nerve stimulation using a commercial, tined SNM lead.

MATERIALS AND METHODS

A custom external research system with stimulation and sensing hardware was connected to the percutaneous extension of an implanted lead during a staged (tined lead) evaluation for SNM. The system collected SER recordings across a range of prespecified stimulation settings (electrode configuration combinations for bipolar stimulation and bipolar sensing) during intraoperative and postoperative sessions in 21 subjects with overactive bladder (OAB) and nonobstructive urinary retention (NOUR). Motor and sensory thresholds were collected during the same sessions.

RESULTS

SERs were detected in all 21 subjects. SER morphology (number of peaks, magnitude, and timing) varied across electrode configurations within and across subjects. Among subjects and electrode configurations tested, recordings contained SERs at motor threshold and/or sensory threshold in 75% to 80% of subjects.

CONCLUSIONS

This study confirmed that implanted SNM leads can be used to directly record SERs elicited by stimulation in subjects with OAB and NOUR. SERs were readily detectable at typical SNM stimulation settings and procedural time points. Using these SERs as possible objective measures of SNM response has the capability to automate patient-specific SNM therapy, potentially providing consistent lead placement, programming, and/or closed-loop therapy.

Effect of pelvic floor muscle training on pelvic floor muscle function and lower urinary tract symptoms in stroke patients: a systematic review

BACKGROUND

Pelvic floor muscle (PFM) dysfunction and lower urinary tract symptoms (LUTS) are common in stroke patients. Although pelvic floor muscle training (PFMT) is a promising intervention, its effects on stroke patients have not been fully studied.

OBJECTIVE

The goal of this study was to conduct a systematic review of the effect of PFMT on PFM and urinary function of stroke patients.

METHODS

The databases AMED, MEDLINE, CINAHL, Cochrane Library, and PEDro were searched for title/abstract on PFMT and stroke. RCTs and quasi-experimental trials that compared the effects of PFMT to a control intervention in stroke patients were included. The RoB 2.0 and ROBINS-I were used to assess the methodological quality of the included studies. The Standardized mean difference (SMD) and its 95% confidence interval (CI) were calculated.

RESULTS

The current review included three RCTs and one quasi-experimental study, all of which were moderate to high quality. The analysis revealed that PFMT significantly improved PFM contraction (SMD: 0.92; 95% CI, 0.47 to 1.38; p < .0001), dynamic endurance (SMD: 0.61; 95% CI, 0.06 to 1.16; p = .030), daytime frequency (SMD: -0.81; 95% CI, -1.37 to -0.25; p = .004), ICIQ-SF (SMD: -1.64; 95% CI, -2.39 to -0.89; p < .0001), and LUTS (SMD: -1.82; 95% CI, -2.67 to -0.96; p < .0001). Differences in PFM strength, static endurance, nocturia, UI frequency, and 24-hour pad weight were insignificant or non-existent between the two groups.

CONCLUSION

This review demonstrates that PFMT improves PFM contraction, PFM dynamic endurance, daytime frequency, and overall LUTS in stroke patients. To validate these findings, well-designed RCTs with large sample sizes and reliable outcome measures should be conducted.

The Influence of Electrode Configuration Changes on the Sensory and Motor Response During (Re)Programming in Sacral Neuromodulation

OBJECTIVES

This study aimed to assess the neurophysiological basis behind troubleshooting in sacral neuromodulation (SNM). Close follow-up of SNM patients with program parameter optimization has proven to be paramount by restoring clinical efficacy and avoiding surgical revision.

MATERIALS AND METHODS

A total of 34 successful SNM patients (28 overactive bladder wet, six nonobstructive urinary retention) with an implantable pulse generator were included. All possible bipolar and monopolar electrode settings were tested at sensory threshold (ST) to evaluate sensory (mapped on a perineal grid with 1 cm² coordinates) and motor (peak-to-peak amplitude and latency of muscle action potential) responses of the pelvic floor. Pelvic floor muscle electromyography was recorded using a multiple array probe, placed intravaginally. Parametric tests were used for paired data: repeated-measures ANOVA or t-test. A nonparametric test was used for paired data: Friedman ANOVA or Wilcoxon signed rank (WSR) test; p < 0.05 was considered statistically significant. If significant, ANOVA was followed by Dunn-Bonferroni post hoc analysis.

RESULTS

Monopolar configurations showed significantly lower STs-1.38 ± 0.73 V vs 1.76 ± 0.89 V (paired t-test: p < 0.0001)-and presented with significantly higher peak-to-peak amplitudes-115.67 ± 79.03 μV vs 90.77 ± 80.55 μV (WSR: p = 0.005)-than bipolar configurations. When polarity was swapped, configurations with the cathode distal to the anode showed significantly lower STs, 1.73 ± 0.91 V vs 1.85 ± 0.87 V (paired t-test: p = 0.003), and mean peak-to-peak amplitudes, 81.32 ± 72.82 μV vs 100.21 ± 90.22 μV (WSR: p = 0.0001). Cathodal changes resulted in more changes in sensory responses than anodal changes (χ² test: p = 0.044). In cathodal changes only, peak-to-peak amplitudes were significantly higher when the distance between electrodes was maximally spread (WSR: p = 0.046).

CONCLUSIONS

From a neurophysiological point of view, monopolar configurations stimulated more motor nerve fibers at lower STs, therefore providing more therapeutic efficiency. Swapping polarity or changing the position of the cathode led to different sensory and motor responses, serving as potential reprogramming options.

Sacral Neuromodulation Changes Pelvic Floor Activity in Overactive Bladder Patients-Possible New Insights in Mechanism of Action: A Pilot Study

OBJECTIVES

To evaluate if electrodiagnostic tools can advance the understanding in the effect of sacral neuromodulation (SNM) on pelvic floor activity, more specifically if SNM induces changes in pelvic floor muscle (PFM) contraction.

MATERIALS AND METHODS

Single tertiary center, prospective study (October 2017-May 2018) including patients with overactive bladder syndrome undergoing SNM. Electromyography of the PFM was recorded using the Multiple Array Probe Leiden. The procedure consisted of consecutive stimulations of the lead electrodes with increasing intensity (1-3, 5, 7, 10 V). Recordings were made after electrode placement (T0) and three weeks of SNM (T1). Patients with >50% improvement were defined as responders, others as nonresponders. For the analyses, the highest electrical PFM response (EPFMR), defined as the peak-to-peak amplitude of the muscle response, was identified for each intensity. The sensitivity (intensity where the first EPFMR was registered and the normalized EPFMR as percentage of maximum EPFMR) and the evolution (EMFPR changes over time) were analyzed using linear mixed models.

RESULTS

Fourteen patients were analyzed (nine responders, five nonresponders). For nonresponders, the PFM was significantly less sensitive to stimulation after three weeks (T0: 1.7 V, T1: 2.6 V). The normalized EPFMR was (significantly) lower after three weeks for the ipsilateral side of the PFM for the clinically relevant voltages (1 V: 36%-23%; p = 0.024, 2 V: 56%-29%; p = 0.00001; 3 V: 63%-37%; p = 0.0002). For the nonresponders, the mean EPFMR was significantly lower at 8/12 locations at T1 (T0: 109 μV, T1: 58 μV; mean p = 0.013, range <0.0001-0.0867). For responders, the sensitivity and evolution did not change significantly.

CONCLUSIONS

This is the first study to describe in detail the neurophysiological characteristics of the PFM, and the changes over time upon sacral spinal root stimulation, in responders and nonresponders to SNM. More research is needed to investigate the full potential of EPFMR as a response indicator.

Pelvic floor activation upon stimulation of the sacral spinal nerves in sacral neuromodulation patients

PURPOSE

To assess the activation of the different parts of the pelvic floor muscles (PFM) upon electrical stimulation of the sacral spinal nerves while comparing the different lead electrode configurations.

MATERIAL AND METHODS

PFM electromyography (EMG) was recorded using an intravaginal multiple array probe with 12 electrodes pairs, which allows to make a distinction between the different sides and depths of the pelvic floor. In addition concentric needle EMG of the external anal sphincter was performed to exclude far-field recording. A medtronic InterStim tined lead (model 3889) was used as stimulation source. Standard SNM parameters (monophasic pulsed square wave, 210 microseconds, 14 Hz) were used to stimulate five different bipolar electrode configurations (3+0-/3+2-/3+1-/0+3-/1+3-) up to and around the sensory threshold. Of each EMG signal the stimulation intensity needed to evoke the EMG signals as well as its amplitude and latency were determined. Linear mixed models was used to analyse the data.

RESULTS

Twenty female patients and 100 lead electrode configurations were stimulated around the sensory response threshold resulting in 722 stimulations and 12 times as many (8664) EMG recordings. A significant increase in EMG amplitude was seen upon increasing stimulation intensity (P < .0001). Large differences were noted between the EMG amplitude recorded at the different sides (ipsilateral>posterior>anterior>contralateral) and depths (deep>center>superficial) of the pelvic floor. These differences were noted for all lead electrodes configurations stimulated (P < .0001). Larger EMG amplitudes were measured when the active electrode was located near the entry point of the sacral spinal nerves through the sacral foramen (electrode #3). No differences in EMG latency could be withheld, most likely due to the sacral neuroanatomy (P > .05).

CONCLUSIONS

A distinct activation pattern of the PFM could be identified for all stimulated lead electrode configurations. Electrical stimulation with the most proximal electrode (electrode #3) as the active one elicited the largest PFM contractions.