Efficacy of Sacral Nerve Stimulation Before Definitive Implantation (SNStest)

Efficacy of Sacral Nerve Stimulation Before Definitive Implantation: a Multicenter Randomized, Double Blind, Crossover Trial

Sacral nerve stimulation (SNS) is an emerging treatment for patients with severe fecal incontinence. The test stimulation is minimally invasive, associated to low morbidity and relatively cheap. On the contrary, implantation of the definite stimulator is related to higher morbidity and considerable costs. A careful patent selection for definite implantation is therefore crucial. However, indication for implantation is actually based only on the subjective criteria reported in the patients´ diary only. Patients and care providers are likely to overestimate the real effect of SNS leading to an unjustified overuse of this expensive device. It is therefore necessary to evaluate real efficacy of SNS during the testing phase in a unbiased setting in order to avoid unnecessary morbidity and costs.

Sacral nerve stimulation (SNS) is an emerging treatment for patients with severe faecal incontinence when conservative measures fail and surgical repair is not indicated. In a minimally-invasive approach and under local anaesthesia, an electrode is placed around sacral nerve root S2-4 and electrical stimulation is applied to the sacral spinal nerves. Effectiveness of SNS is definitively not only explained by placebo effect but the pathophysiologic mechanisms remain unclear. Suggested pathways include modulation of afferent nerve fibres and direct stimulation of the pelvic floor and anal sphincter muscle. After placement of the electrode, the patient is stimulated by an external stimulator for 1-3 weeks. During this period, the patient documents the number of faecal incontinence episodes or urgencies in a symptom diary. By convention, indication for permanent stimulation is based on a 50% reduction in the number of episodes. After a successful testing period, the permanent stimulator is implanted, generally in the upper gluteal region. Previous studies report success rates up to 80%. The only randomized trial with a proper sample size evaluated the efficacy of SNS after definite implantation. In this study, 63% of the patients felt improved during the placebo period and might not really benefit from the device. The real success rate of SNS is therefore likely to be considerably lower. Efficacy of SNS during the testing phase has never been assessed in a blinded randomized study.

Primary success rate of SNS after 7 days. By convention this is assessed by >50% reduction in the number of episodes in the symptom diary.

Inclusion Criteria: All patients admitted to SNS test for treatment of faecal incontinence after unsuccessful conservative (or surgical) treatment. Exclusion criteria: Absence of informed consent. Patients not speaking french or german.