The very limited evidence from the included studies suggests that SNS can improve continence in selected people with faecal incontinence, and reduce symptoms in selected people with constipation. However temporary, percutaneous stimulation for a two-to-three week period does not always successfully identify those for whom a permanent implant will be beneficial. Larger, good quality randomised crossover trials are needed to allow the effects of SNS for these conditions to be assessed with more certainty.
Double-blind crossover study of sacral nerve stimulation for fecal incontinence.
Patients with fecal incontinence not amenable to simple repair may have to undergo major reconstructive surgery or resort to a stoma. Sacral nerve stimulation is an alternative approach that may diminish incontinence by altering sphincter and rectal motor function. This study is the first double-blind trial examining the effectiveness of this therapy.
                Two patients with passive fecal incontinence who had been implanted for nine months with a permanent sacral nerve stimulator and electrode were studied using fecal incontinence diaries, anorectal physiological tests, and quality-of-life assessments (SF-36 health survey). The trial period consisted of two two-week periods, with the stimulator turned on for two weeks and off for two weeks. The main investigator and the patients were blinded to the status of the stimulator.
                There was a dramatic difference between the number and severity of episodes of incontinence when the stimulator was turned on vs. turned off (Patient 1, 20 vs. 2 episodes; Patient 2, 4 vs. 0 episodes; off vs. on). There was an increase in squeeze pressure (Patient 1, 70 vs. 100 cm H2O; Patient 2, 60 vs. 90 cm H2O; off vs. on), with moderate increases in resting pressure and rectal threshold and urge volumes. Quality-of-life measurements showed a marked improvement prestimulation vs. nine months after permanent stimulation.
                There is a marked, unequivocal improvement in symptoms of fecal incontinence with sacral nerve stimulation shown in this double-blind crossover trial. Sacral nerve stimulation improves the quality of life in selected patients with fecal incontinence.