Sacral root stimulation for controlled defecation

Abstract

Selective rectal or sphincter neurostimulation aiming at controlled defecation was performed in 10 dogs. While the dogs were under anesthesia, the rectal and rectal neck pressures, balloon expulsion as well as external anal sphincter (EAS) response to stimulation of the second sacral ventral nerve root (S2) and its autonomic and somatic branches were determined. Each of these nerves was stimulated separately using bipolar platinum cuff electrodes. S2 stimulation resulted in rectal and rectal neck pressure elevation as well as increase of EMG activity of EAS without balloon expulsion. Autonomic branch stimulation effected rectal pressure increase and balloon expulsion, while somatic branch stimulation caused increase of rectal neck pressure and EAS EMG activity with no balloon expulsion. S2 stimulation with somatic branch transection produced rectal pressure elevation and balloon expulsion. In contrast to rectal pressure, the rectal neck pressure increased with increasing stimulus frequency. In conclusion, rectal evacuation and sphincteric control could be induced by selective sacral root electrostimulation: S2 stimulation with transection of the somatic branch for the former and pudendal branch stimulation for the latter.