Improving the efficacy of sacral nerve stimulation for faecal incontinence by alteration of stimulation parameters

BACKGROUND: Sacral nerve stimulation (SNS) is an effective treatment for faecal incontinence, but only standard stimulation parameters have been used. This study assessed the clinical impact of altering the parameters. METHODS: Twelve patients with partially improved faecal incontinence following SNS underwent acute testing to select optimal stimulation parameters; rectal compliance was used as a surrogate marker. Parameters tested were: stimulation off; frequency 14 (standard), 31 or 6.9 Hz; and pulse duration 210 (standard), 450 or 90 micros. Patients completed a 2-week bowel diary, St Mark's continence score (SMCS) and Rockwood faecal incontinence quality-of-life (FIQL) score before testing using standard settings, and after testing using optimized settings. RESULTS: Optimal settings, determined by greatest increase in rectal compliance, were shorter pulse width in five patients and higher frequency in seven. Optimized stimulation resulted in a decrease in mean episodes of incontinence from 2.3 to 1.2 per week (P = 0.031), soiling from 3.3 to 1.7 days per week (P = 0.016), faecal urgency from 31 to 18 per cent of all evacuations (P = 0.055) and SMCS from 12.3 to 8.7 (P = 0.008); the FIQL coping/behaviour score improved (P = 0.008). CONCLUSION: With a shorter pulse width and higher frequency, clinical efficacy in patients undergoing SNS for faecal incontinence can be improved.