Sacral Nerve Stimulation for Fecal Incontinence

Overview of the Procedure

A sacral nerve stimulation (SNS) trial involves a two-stage approach, with the first stage being the peripheral nerve evaluation (PNE) test to determine if a patient is a suitable candidate for permanent implantation, as recommended by the American Gastroenterological Association 1, 2
During the PNE test, temporary electrodes are placed percutaneously in the sacral foramina (typically S3) and connected to an external electrical stimulator for a period of 2-3 weeks, with a response rate of 50% or more considered a good candidate for permanent implantation 1

SNS is indicated for patients with fecal incontinence who have failed conservative therapies, with most clinical trials focusing on patients with a structurally intact anal sphincter or a defect smaller than 120° 1, 2
Patients with significant anatomical defects should have these corrected surgically before considering SNS, according to the American Gastroenterological Association 3

In the pivotal US multicenter trial, 90% of 133 patients proceeded from temporary to permanent stimulation, with long-term follow-up data showing 36% of patients achieved complete continence, and 89% were deemed therapeutic successes 1
Controlled studies have shown SNS to be significantly better than medical treatment for fecal incontinence, with a strength of evidence rated as high 1, 4

The most common adverse events include pain at the insertion site (up to 10% of patients) and infection at the insertion site (up to 10% of patients) 1, 2

If the trial is successful (≥50% reduction in fecal incontinence episodes), a permanent stimulator is implanted beneath the skin, with the battery needing replacement approximately every 7 years 1, 2
Alternative approaches for patients who fail SNS include ongoing medical management, evaluation for pelvic floor structural abnormalities, management of colonic motor dysfunction, and consideration of anterograde colonic enema procedures 2

The mechanism of action of SNS is not fully understood, but may involve inducing colonic retrograde propagated sequences that delay colonic transit, with a potential placebo effect observed in some patients 1