Colonosphincteric electromyographic responses to sacral root stimulation: evidence for a somatosympathetic reflex

Abstract

The aim of the present study was to determine the effects of selectively stimulating the afferent fibres running in the dorsal sacral roots (S1, S2, S3) and the somatic (radial and sciatic) nerves on colonic and internal anal sphincter (IAS) electromyographic (EMG) activity in anaesthetized cats to try to understand how sacral nerve stimulation can improve fecal continence in human. Electrically stimulating the afferent fibres present in the sacral dorsal roots and somatic nerves inhibited the colonic spike potential frequency (n = 97) and increased the slow variations in the sphincteric membrane potential (n = 76). These effects were found to have disappeared after administering an alpha-noradrenergic receptor blocker (n = 64) or sectioning the sympathetic efferent fibres innervating these organs (n = 69) suggesting the involvement of the sympathetic system in the effects observed. Moreover, no significant differences were observed between the effects of sacral dorsal root vs somatic nerve stimulation on colonic and sphincteric EMG activity. In conclusion, the data obtained here show that neurostimulation applied to the sacral spinal roots may improve fecal continence by inhibiting colonic activity and enhancing IAS activity via a somatosympathetic reflex.

Sacral Nerve Stimulation can Improve Continence in Patients with Crohn's Disease with Internal and External Anal Sphincter Disruption

“…12 A recent study in cats also indicated that SNS may improve fecal continence by inducing an inhibition of electromyographic activity of the colon, probably via a somato-sympathetic reflex. 13 These results may help to explain how SNS improves fecal continence in patients in whom both anal sphincters are impaired.…”

Transcutaneous Posterior Tibial Nerve Stimulation for Fecal Incontinence in Inflammatory Bowel Disease Patients: A Therapeutic Option?

“…In a recent work we have shown, in the cat, that stimulating the sacral spinal roots may improve fecal continence by enhancing internal anal sphincter electromyographic activity and by inhibiting colonic electromyographic activity via a somatosympathetic reflex. 19 We have also demonstrated that stimulating the somatic afferent fibers induces the same effects on colonic and internal anal activity. This somatosympathetic reflex may explain in part the positive effect of posterior tibial nerve stimulation on fecal incontinence.…”

Incontinence fécale et stimulation des racines sacrées

“…Dans ces conditions, il était logique que les patients présentant une lésion anatomique du sphincter anal externe significative, soient considérés comme de moins bons candidats pour ce traitement. Actuellement, il semble plus probable que la stimulation sacrée améliore la continence anale en modulant la motricité colo-rectale [26] et/ou la sensibilité rectale [19] voire le contrôle cérébral des organes périnéaux [27]. Aussi, des études préliminaires [9,10,28,29] ont évalué l'efficacité de la stimulation sacrée chez les patients incontinents anaux présentant une lésion du sphincter anal externe.…”

“…Plusieurs études ont attiré l'attention sur une réduction de la motricité colique au cours de la stimulation sacrée [18,26,45,46]. Vitton et al, ont démontré une inhibition de la motricité colique par stimulation des racines dorsales sacrées chez le chat qui mettrait en jeu un réflexe somato-sympathique (stimulation des afférences pelviennes entraînant un effet médullaire avec activation du système sympathique sacrée) [26]. Chez l'homme, Michelsen et al ont observé une augmentation significative du transport rétrograde du colon gauche et une tendance à l'augmentation du temps de transit chez des patients incontinents anaux traités par stimulation des racines sacrés [18].…”