Clinical utility of trans‐sacral magnetic stimulation‐evoked sphincter potentials and high‐density electromyography in pelvic floor assessment: Technical evaluation

AIM: Faecal incontinence is common and of multifactorial aetiologies, yet current diagnostic tools are unable to assess nerve and sphincter function objectively. We developed an anorectal high-density electromyography (HD-EMG) probe to evaluate motor-evoked potentials induced via trans-sacral magnetic stimulation (TSMS). METHOD: (MagStim Company). Patients undergoing pelvic floor investigations were recruited for this IDEAL Stage 2a pilot study. RESULTS: Eight participants (median age 49 years; five female) were recruited. Methodological viability, safety and diagnostic workflow were established. The test was well tolerated with median discomfort scores ≤2.5/10, median pain scores ≤1/10 and no adverse events. Higher Faecal Incontinence Severity Index scores correlated with longer MEP latencies (r = 0.58, p < 0.001) and lower MEP amplitudes (r = -0.32, p = 0.046), as did St. Mark's Incontinence Scores with both MEP latencies (r = 0.49, p = 0.001) and MEP amplitudes (r = -0.47, p = 0.002). CONCLUSION: This HD-EMG probe in conjunction with TSMS presents a novel diagnostic tool for anorectal function assessment. Spatiotemporal assessment of magnetically stimulated MEPs correlated well with symptoms and offers a feasible, safe and patient-tolerable method of evaluating pudendal nerve and external anal sphincter function. Further clinical development and evaluation of these techniques is justified.