Sacral Neuromodulation with ultra-low stimulation intensity is effective in faecal incontinence – results from a randomised study with a One-stage implant procedure

In Sacral Neuromodulation(SNM), the stimulation intensity is set at the sensory threshold(ST) level. However, subsensory stimulation at 50% of ST has proven effective in reducing faecal incontinence episodes. Aim : To explore the relationship between functional outcomes and varying subsensory stimulation amplitude in newly implanted patients. Method : This randomised, double-blinded study was designed to include patients with ≥ 1faecal incontinence episodes/week despite maximal conservative therapy. As part of another trial, patients were offered a one-stage procedure. Postoperatively, patients were randomised into two groups. G-1: Received stimulation at 0.05 volts, 50 and 90% of ST in 3x4-week periods, followed by 12-weeks stimulation at the ST. G-2: Received stimulation with 90% of the ST in in 3x4-week periods, followed by 12-weeks stimulation at ST. Patients were evaluated after each period using St. Marks’s Incontinence Score, Visual-Analog-Scale(VAS) for patient satisfaction regarding social function, bowel function and quality-of-life, along with a bowel habit diary. Results : Seventy-three patients with a median age of 60(IQR:50–69) completed the trial. Faecal incontinence episodes were significantly reduced at all follow-ups, with no differences between groups. The only statistical difference between groups was deltaVAS for bowel function after 4-weeks. In G-1 with ultralow stimulation amplitude (0.05 volts - equivalent to 9.6(IQR:6.5–13.4)% of ST) the improvement compared to baseline was 30(IQR:10–50) points significantly lower than G-2 with an improvement of 50(IQR:10–70) points (p-value: 0.05). Conclusion : Subsensory stimulation is feasible in newly implanted patients with faecal incontinence. An amplitude of 0.05 volts, is as effective on the functional outcomes as stimulation with higher amplitudes.