Factors Affecting Anal Sphincter Recruitment During Intraoperative Pudendal Nerve Stimulation: An Observational Study

Area of Science:

• Neurology
• Urology
• Biomedical Engineering

Background:

• Pudendal neuromodulation is used for lower urinary tract symptoms and pelvic pain.
• Factors influencing external anal sphincter (EAS) recruitment in pudendal neuromodulation are not fully understood.

Purpose of the Study:

• To identify and quantify patient and stimulation factors affecting EAS recruitment and outcomes.
• To optimize pudendal neuromodulation for treating lower urinary tract symptoms and pelvic pain.

Main Methods:

• Observational study of 16 participants receiving pudendal neuromodulation.
• Recorded EAS activation during lead implantation.
• Used MRI/CT to measure electrode-to-nerve distance.
• Applied linear mixed modeling to analyze factors affecting EAS recruitment.

Main Results:

• Participant demographics (sex, age, BMI) did not significantly impact EAS recruitment.
• Pulse width of 210 µs balanced current and charge for EAS activation.
• Increased electrode-to-nerve distance reduced EAS response magnitude and increased activation threshold.
• Greater electrode-to-nerve distance correlated with poorer bladder symptom improvement.

Conclusions:

• A pulse width of 210 µs is optimal for EAS recruitment.
• Minimizing electrode-to-nerve distance is crucial for successful lead implantation.
• EAS activation threshold and response magnitude can indicate electrode-to-nerve proximity.