Dose Response Curve - Sacral Nerve Stimulation for Faecal Incontinence

Faecal incontinence is a devastating condition with huge impact on quality of life. Sacral Nerve Stimulation (SNS) has since 1995 been a treatment option for patients not obtaining satisfactory continence result with standard non-surgical treatments. SNS is electrical stimulation of the sacral nerve root(s2,3 or 4). Stimulation of this nerve roots results in improved continence. The mechanism of action is at present not well described.

Standard the neuromodulator (pacemaker) stimulate with Frequency 14 Hz, pulse width 210 mic.sec. and amplitude set at sensory threshold. One study by SM. Koch et all confirms that subsensory stimulation can be effective. At present there is no doubled blinded study's to confirm this theory of effective sub sensory stimulation.

The aim of this study is to determine if subsensory stimulation will be as effective as stimulation with amplitude at sensory threshold. This will be investigated in 20 patients who have had at least a reduction in incontinence episodes or Wexner inc. score of 75 % between preimplantation and latest follow up. The patients will be randomized to three different amplitudes. 1: amplitude set at sensory threshold. 2: 75% of sensory threshold. 3: 50% of sensory threshold. The order of the three settings will be random and in a double blinded manner. The interval between these three pacemaker settings is four weeks. Patients serve as there own controls. Stimulation frequency (14 Hz) and pulse width (210 mic-sec) will remain fixed.

Evaluation will be by means of 4 week bowel habit diary and questionnaires (Wexner inc. score / St. Marks Score / Wexner constipation score / Altomares OD-score / IBS-score/ Rockwood FIQoL -score). All patients will be evaluated with anorectal measurements (sphincter strength and anorectal volume measurements) before any changes of stimulation amplitude.