Evoked Spinal Cord Potentials Monitored at Thoracoabdominal Region after Trans-intercostal Stimulation

To investigate the feasibility of a novel recording method for trans-intercostal evoked spinal cord potentials (Tic-ESCPs) and the properties of the waveforms, the potentials were recorded and analyzed in an animal model. In two beagle dogs, Tic-ESCPs were recorded at the left twelfth intercostal to fourth lumbar nerves following stimulation at the left eleventh intercostal nerve, either with or without the use of a muscle relaxant. The amplitude and latency of the Tic-ESCP waves were then measured and compared with those of conventional transcranial spinal motor evoked potentials (MEPs). Tic-ESCPs could be obtained at any nerve, with or without the use of a muscle relaxant. The Tic-ESCP waveform was clear and simple, consisting of a small positive (P1) wave and a subsequent large negative (N1) wave. As the site of recording moved farther from the stimulation site, the N1 amplitudes were reduced and the P1 latency was prolonged. Under muscle relaxation, the N1 amplitudes were reduced, and the P1 latencies were shorter. As compared with MEPs, Tic-ESCPs could be evoked by a weaker stimulus, the N1 amplitude was smaller, and the P1 latency was shorter. Tic-ESCP recording was feasible either with or without the use of a muscle relaxant. The Tic-ESCPs showed simple and clear waveforms with smaller stimulations. Therefore, Tic-ESCPs may be useful for intraoperative spinal cord monitoring.