Bipolar transesophageal thoracic spinal cord stimulation: A novel clinically relevant method for motor-evoked potentials

Abstract

Objective: Although transesophageal motor-evoked potential elicited by monopolar cervical cord stimulation is more stable and rapid in response to ischemia than transcranial motor-evoked potential in canine experiments, direct cervical alpha motor neuron stimulation precludes clinical application. We evaluated a novel stimulation method using a bipolar esophageal electrode to enable thoracic cord stimulation.Methods: Twenty dogs were anesthetized. For bipolar transesophageal stimulation, the interelectric pole distance was set at 4 cm. Changes in amplitude in response to incremental stimulation intensity (100-600 V) were measured to evaluate stability. Spinal cord ischemia was induced by aortic balloon occlusion at the T8 to T10 level for 10 minutes to evaluate response time or at the T3 to T5 level for 25 minutes to evaluate prognostic value. Neurological function was evaluated using the Tarlov score at 24 and 48 hours postoperatively.Results: Bipolar transesophageal stimulation was successful in all animals and their forelimb waveforms were identical to those after transcranial stimulation. The minimum stimulation intensity to produce >90% of the maximum amplitude was significantly lower in both monopolar and bipolar transesophageal stimulation than in transcranial stimulation (n ¼ 5). Time to disappearance and recovery (>75%) of the hindlimb potentials were significantly shorter by both monopolar and bipolar transesophageal stimulation than by transcranial stimulation (n ¼ 5). Correlation with neurological outcomes was comparable among all stimulation methods (n ¼ 10).Conclusions: Motor-evoked potential can be elicited by bipolar transesophageal thoracic cord stimulation without direct cervical alpha motor neuron stimulation, and its stability and response time are comparable to those elicited by monopolar stimulation. (JTCVS Techniques 2020;4:28-35) Forelimb potentials by thoracic cord stimulation are evoked through synaptic transmission.

Risk Factors for Spinal Cord Injury during Endovascular Repair of Thoracoabdominal Aneurysm: Review of the Literature and Proposal of a Prognostic Score

“…Due to the risk of false-positive results in neuromonitoring, experimental research is being conducted to improve the technique. Transesophageal MEP has been reported to provide a shorter response time in animal models [60]. Research into the possibility of stimulating and recording intercostal nerve activity has also been published [61].…”

Commentary: Transoesophageal stimulation for spinal chord monitoring: Catchy but still experimental!

“…Yamanaka and colleagues 1 present a bipolar transesophageal thoracic spinal cord stimulation method that elicits motor-evoked potentials without direct cervical alpha motor neuron stimulation.…”

Commentary: Going transesophageal will make your monitoring simpler!

“…In this issue of the Journal , Yamanaka and colleagues 7 present an elegant animal experiment performed to evaluate a novel method using a bipolar esophageal electrode to enable thoracic cord stimulation. These authors previously showed in canine experiments that measurement of monopolar transesophageal motor-evoked potentials (m-TE-MEP) is feasible, safe, and superior to TC-MEP in terms of stability, response time to ischemia/reperfusion, and prognostic value.…”