Sacral Neuromodulation for Fecal Incontinence A Review of the Central Mechanisms of Action

Objective: Fecal incontinence (FI) has a devastating effect on the quality of life and results in social isolation. Sacral neuro-modulation (SNM) is proven to be an effective, minimal invasive treatment modality for FI. Despite the increasing application of SNM, the exact mechanisms of action remain unclear. The initial assumption of peripheral motor neurostimulation is not supported by increasing evidence, which report effects of SNM outside the pelvic floor. A new hypothesis states that afferent signals to the brain are essential for a successful therapy. This study aimed to review relevant studies on the central mechanism of SNM in FI. Methods: Clinical and experimental studies on the central mechanisms, both brain and spinal cord, of SNM for FI up to December 2015 were evaluated. Results: In total, 8 studies were found describing original data on the central mechanism of SNM for FI. Four studies evaluated the central effects of SNM in a clinical setting and 4 studies evaluated the central effects of SNM in an experimental animal model. Results demonstrated a variety of (sub) cortical and spinal changes after induction of SNM. Conclusion: Review of literature demonstrated evidence for a central mechanism of action of SNM for FI. The corticoanal pathways, brainstem, and specific parts of the spinal cord are involved.