Stimulus Threshold For Providing Intraoperative Motor Evoked Potential

Aim: Intraoperative neurophysiological monitoring (IOM) has been increasingly used in surgeries associated with a risk of neurological impairment. Motor evoked potential (MEP), which is a part of intraoperative neurophysiological tests, evaluates motor function intraoperatively. Most anesthetic agents have negative effect on neurophysiologic recordings because of neuronal excitability changes. Our aim was to compare the effect of anesthetic methods consisting of volatile anesthetics and intravenous anesthetics (propofol + remifentanil) on eliciting of MEP during baseline recordings for spinal surgery which is a part of neurosurgical operations.Methods: Fifty patients (29 males and 21 females; 21 to 85 years) who underwent spinal surgery with IOM in our department between 2016 and 2018 were randomly chosen for retrospective evaluation. A multipulse stimulation technique (6-9 stimuli) was used for electrical stimulation.Results: There was a statistically significant difference in stimulus threshold in voltage stimulation between the two groups. In order to elicit muscle MEP, a higher voltage threshold had to be implemented for patients who had been given volatile anaesthesia compared to those who had been given total intravenous anesthesia (TIVA) (Mann-Whitney U test, p<0.005).Conclusion: TIVA is considered better than volatile for eliciting muscle MEPs in lower stimulus threshold. In addition, TIVA provides easy recording in all proximal and distal muscles.