Motor Evoked Potentials Monitoring During Neurosurgical Operations on the Spinal Cord

Summary

In order to monitor descending pathways during neurosurgical operations on the spinal cord, motor evoked potentials (MEPs) were recorded from the thenar and anterior tibial muscles and from the epidural space along the spinal cord and the cauda equina in a total of 83 patients following transcranial electrical cortex stimulation. It was the aim of our study to find out whether MEP monitoring is a reliable and sensitive method for the detection of impending motor deficits. Interaoperative recordability of potentials was 79.7%. On the basis of acceptable changes in amplitudes of up to 50% at the end of surgery, 82.7% of the recordings correlated correctly with the postoperative motor status; there were false positive results in 17.3%. We did not observe false negative correlation. In conclusion, intraoperative MEP monitoring is a sensitive method for the detection of impending motor defi­cits. Major problems concern the influence of anesthesia, the definition of acceptable limits for changes in potentials, and the most suitable stimulation and recording techniques.