# Clinical efficacy of subsensory sacral neuromodulation in adults with faecal incontinence: The SUBSoNIC crossover randomised controlled trial and cohort follow‐up study

## TL;DR

This study tested if subsensory sacral neuromodulation helps reduce fecal incontinence in adults but found no strong evidence of effectiveness.

## Contribution

The study is the first randomized crossover trial to rigorously evaluate the clinical efficacy of subsensory sacral neuromodulation for fecal incontinence.

## Key findings

- SNM showed a non-significant reduction in fecal incontinence episodes compared to sham treatment.
- Improvements in symptoms were observed at 58 weeks compared to baseline.
- The trial failed to provide conclusive evidence of SNM's experimental efficacy.

## Abstract

Sacral neuromodulation (SNM) is considered the first‐line surgical treatment in adults with refractory faecal incontinence (FI). However, its clinical efficacy has not been rigorously tested in a trial setting.

Randomised, multicentre, double‐blind crossover trial (two 16‐week periods) of active stimulation versus sham, and open‐label follow‐up to 58 weeks. Participants: adults aged 18–80 with refractory FI. Interventions: Active: subsensory sacral nerve stimulation with an implanted pulse generator; Sham: identical implant but turned off. Primary outcome: FI episodes per week (paper bowel diary) during final 4 weeks of crossover periods (allowing 12 weeks' washout). Randomised allocation (1:1) to arm 1 (SNM/sham) or arm 2 (sham/SNM). Blinding: participants, surgeons, assessors; tamper‐proof tape‐masked stimulation settings. Sample size: 80 patients to detect a 30% reduction in episodes. Groups compared using a paired t‐test, and treatment effects summarised by mean differences.

Trial delivery was severely affected by COVID‐19. Thirty‐nine patients of 220 screened (arm 1: N = 17; arm 2: N = 22) were recruited at 10 sites (February 2018–July 2022), of whom only 16 (arm 1: N = 9; arm 2: N = 7) had complete primary outcome data. Of the 39, 19 completed follow‐up to 58 weeks. SNM conferred a non‐significant reduction in mean FI episodes per week compared to sham (−0.795 [95% CI: −1.5 to 0.0], p = 0.06). Improvements were observed in FI symptoms at 58 weeks compared to baseline (FI episodes per week: 3.2 [SD 3.3] vs. 6.2 [SD 5.9]).

The SUBSoNIC trial failed to find conclusive evidence of the experimental efficacy of SNM. Further demonstration of experimental efficacy remains important as SNM is a high‐cost and invasive therapy.