What is sacral nerve stimulation and is it appropriate for a patient with hyper‑tonic levator ani and dyssynergic defecation refractory to biofeedback?

Sacral Nerve Stimulation for Hypertonic Levator Ani and Dyssynergic Defecation

Sacral nerve stimulation (SNS) is NOT appropriate for your patient with hypertonic levator ani and dyssynergic defecation refractory to biofeedback, as there is no evidence that SNS improves bowel symptoms or rectal evacuation in defecatory disorders. 1

What is Sacral Nerve Stimulation?

SNS involves continuous pulsed electrical stimulation of the sacral nerves (typically S3) using a battery-operated stimulator implanted beneath the skin. 1 The procedure uses a two-stage approach:

• Stage 1 (Peripheral Nerve Evaluation): A temporary electrode is placed percutaneously in the sacral foramen and connected to an external stimulator for 2-3 weeks. 1, 2
• Stage 2 (Permanent Implantation): If fecal incontinence frequency declines by ≥50%, a permanent stimulator is implanted subcutaneously. 1, 2
• Battery replacement is required approximately every 7 years. 1, 3

Evidence for SNS in Defecatory Disorders

The evidence directly contradicts using SNS for your patient's condition:

• A randomized, double-blind, placebo-controlled crossover study found that neither sub- nor supra-sensory SNS increased the proportion of complete bowel movements compared to sham SNS in 55 patients with medically-refractory slow transit constipation and normal anorectal functions. 1
• While one uncontrolled European multicenter trial showed improvement in bowel symptoms (frequency, straining, incomplete evacuation) in 45 of 62 constipation patients, this study included primarily slow transit constipation (81%), not dyssynergic defecation. 1
• The American Gastroenterological Association explicitly states "there is no evidence that SNS improves bowel symptoms or rectal evacuation in defecatory disorders." 1

Appropriate Indications for SNS

SNS is highly effective for fecal incontinence, not constipation or dyssynergic defecation:

• In the pivotal US multicenter trial for fecal incontinence, 90% of 133 patients proceeded to permanent implantation, with 36% achieving complete continence and 89% deemed therapeutic successes at 5-year follow-up. 1, 2
• SNS is significantly better than medical treatment for fecal incontinence (high strength of evidence). 1, 2
• Most trials limited enrollment to patients with structurally intact anal sphincters or defects <120°. 1, 2

Appropriate Management for Your Patient

When dyssynergic defecation fails biofeedback therapy, the recommended options are: 1

1. Ongoing medical management with emphasis on suppositories and enemas 1, 3
2. Evaluation for pelvic floor structural abnormalities (clinically significant rectoceles or enteroceles) with appropriate surgical management 1, 3
3. Management of colonic motor dysfunction with prokinetic agents 1, 3
4. Consider botulinum toxin injection into the anal sphincter for hypertonic levator ani 1

Common Pitfalls to Avoid

• Do not confuse fecal incontinence with constipation/dyssynergic defecation when considering SNS—the evidence base is completely different. 1
• Do not proceed with SNS based on uncontrolled studies when high-quality RCTs show no benefit for defecatory disorders. 1
• The mechanism of SNS remains poorly understood, with crossover studies showing equal symptoms whether the stimulator is on or off, suggesting potential placebo effects. 1, 2

Complications of SNS

If SNS were to be considered (which it should not be for this indication), be aware that:

• Pain and infection at the insertion site occur in up to 10% of patients. 1, 3, 2
• The cost is substantial at $35,818 (2013 dollars). 1