Surface Electromyography Reliably Records Electrophysiologically Evoked Internal Anal Sphincter Activity: A More Minimally Invasive Approach for Monitoring Extrinsic Innervation

Abstract

Background: Even in the case of minimally invasive pelvic surgery, sparing of the autonomic nerve supply is a prerequisite for maintaining anal sphincter function. Internal anal sphincter (IAS) innervation could be electrophysiologically identified based on processed electromyographic (EMG) recordings with conventional bipolar needle electrodes (NE). This experimental study aimed for the development of a minimally invasive approach via intra-anal surface EMG for recordings of evoked IAS activity. Methods: Six male pigs underwent nerve-sparing low anterior rectal resection. Electric autonomic nerve stimulations were performed under online-processed EMG of the IAS. EMG recordings were simultaneously carried out with conventional bipolar NE as the reference method and newly developed intra-anal surface electrodes (SE) in different designs. Results: In all experiments, the IAS activity could be continuously visualized via EMG recordings based on NE and SE. The median number of bipolar electric stimulations per animal was 27 (range 5-52). The neurostimulations resulted in significant EMG amplitude increases for both recording types [NE: median 3.0 µV (interquartile range, IQR 2.8-3.5) before stimulation vs. 7.1 µV (IQR 3.9-13.8) during stimulation, p < 0.001; SE: median 3.6 µV (IQR 3.1-4.3) before stimulation vs. 6.8 µV (IQR 4.8-10.3) during stimulation, p < 0.001]. Conclusions: Intra-anal SE enabled reliable EMG of electrophysiologically evoked IAS activity similar to the conventional recording via NE. The transfer of the method to access platforms for transanal total mesorectal excision or robotics may offer a practical more minimally invasive approach for monitoring extrinsic innervation.

Transcutaneous sacral nerve stimulation for intraoperative verification of internal anal sphincter innervation

“…Furthermore, 9×5 cm carbon anodes (AAM GmbH, Triberg, Germany) were placed on the back, right and left thigh, and lower abdomen. The newly developed intra‐anal surface probe (Fraunhofer IBMT, St. Ingbert, Germany) with it's distal stainless steel contact served as an additional anode (Figs. and ).…”

Postprocessing algorithm for automated analysis of pelvic intraoperative neuromonitoring signals

“…Anesthesia was carried out with intravenous thiopental sodium (Trapanal ® , Nycomed, Germany) and Piritramid (Dipidolor ® , Janssen-Cilag, Germany). The perioperative management has been described by Kauff et al [5]. For EMG recording a bipolar needle electrode (Art.-No.…”

“…Additional intra-anal surface EMG of IAS was realized with a newly developed electrode design. This electrode was equipped with two conductive silicone electrode contacts which were arranged circularly for recording [5].…”

Multifractal characteristics of external anal sphincter based on sEMG signals

“…All those methods can cause significant stool continence related problems hence proper assessment of anorecatal innervation before and after the treatment can be crucial for prevention and treatment of complications. sEMG enables non-invasive monitoring of the anal sphincter function [4,5,6] and is a very promising method of testing of innervation of muscles. Since innervation deficits are one of suggested mechanisms for severe treatment related complications in up to 40% of rectal cancer patients development of proper innervation assessment methodology is crucial.…”