Effects of stimulation frequency and intensity in sacral neuromodulation on anorectal inputs to the somatosensory cortex in an experimental model

Introduction Although sacral neuromodulation (SNM) is an established treatment for faecal incontinence, stimulation parameters have been derived empirically and only one frequency (14 Hz) is employed clinically. The aim of this study was to test a range of stimulation frequencies to establish an optimal frequency of SNM for maximum augmentation of anal canal cortical evoked potentials (EPs) in an animal model. Methods In female Wistar rats, anal canal EPs were recorded over the primary somatosensory cortex using a flexible multielectrode array, and the effect of SNM was studied. SNM was applied at 0·1–100 Hz and a frequency response curve plotted. The data were fitted to a quadratic equation. Results The magnitude of potentiation of anal canal EPs caused by SNM depended significantly on stimulation frequency (P