Improved longevity and efficacy of sacral nerve stimulation by simple adjustments at follow-up.

Abstract

Sacral nerve stimulation (SNS) for faecal incontinence (FI) at subsensory amplitudes as low as 50% of the sensory threshold has been found to be effective at 3 months' follow-up. Furthermore, alternative pacemaker settings may improve functional outcome in patients with suboptimal treatment efficacy. In this work we aim to explore if sub-sensory stimulation as low as 50% of sensory threshold is effective at 1-year follow-up. We also aimed to investigate if 31Hz (frequency) or 90µs (pulse width) stimulation improved treatment efficacy in dissatisfied patients. All patients in whom the stimulation was effective in controlling FI (satisfied group) were encouraged to have the stimulation amplitude reduced. Those in whom the device was less effective (dissatisfied group) were offered alternative frequency settings or pulse width (31Hz or 90µs). Patients were follow-up after 12 months and evaluated by a visual analogue scale (VAS) for patient satisfaction, the Cleveland Clinic Continence Score (CCCS), Rockwood Faecal Incontinence Quality of Life Scale (QoL) and a bowel habit diary. Two hundred and nineteen patients were contacted, with a response rate of 71% (n=155). Those who were successfully contacted comprised 110 (71%) patients classed as satisfied and 45 (29%) as dissatisfied. Seventy-five (68%) of the satisfied patients agreed to have their stimulation amplitude reduced. At 1-year follow-up the median amplitude had reduced from 1.5 V [interquartile range (IQR) 0.85-2.0 V] to 0.75 V (IQR 0.45-1.4 V) (P-value <0.001) representing an overall reduction of 39% (6.6-62.5%). There were no significant differences in VAS, CCCS or QoL despite subsensory stimulation at 1-year follow-up. In 28% of the dissatisfied patients alternative pacemaker settings improved VAS to satisfactory levels. Subsensory stimulation is as effective as stimulation at or above the sensory threshold. High-frequency stimulation (31Hz) can improve functional outcome in patients with loss of efficacy.