RELATIONSHIP BETWEEN EVOKED-POTENTIALS AND CLINICAL STATUS IN SPINAL-CORD ISCHEMIA

Study Design. Sciatic neurogenic motor-evoked potentials (sciatic-NMEP ), spinal-evoked potentials (spinal-EP), and somatosensory-evoked pote ntials (SEP) were recorded in the lumbar cord during progressive ligat ion of segmental arteries. Relationship between electrophysiologic ass essment and clinical status was studied. Objectives. In 12 anesthetize d dogs that had arterial ischemia of the lumbar cord produced by ligat ion of segmental arteries, the aforementioned evoked potentials were r ecorded, and their presence or absence was compared with the clinical status of repeated wake-up tests. Summary of Background Data. Both sci atic-NMEP loss and ligation level producing cord ischemia were not ass ociated with severity of wake-up test. Sciatic-NMEPs were lost earlier than spinal-EP and SEPs after progressive ligation. The false-negativ e rate of sciatic-NMEP, SEP at high spine and at low spine was 12.5%, 20.8%, and 41.7%, respectively. The waveform morphology of potentials by cord ischemia decreased in amplitude and in the number of peaks wit hout a shift of latency. Methods. First, baseline NMEPs and SEPs were obtained, lumbar arteries were ligated, evoked potentials were recorde d continuously, and wake-up test was administered. If sciatic-NMEPs we re not lost, intercostal arteries were ligated, and potentials and cli nical status were reassessed. Results. Though these results were compl icated, sciatic-NMEP was more sensitive to the spinal cord ischemia an d a better predictor of clinical outcome than spinal-EP and SEP. Howev er, the presence was not a guarantee of normal function. Somatosensory -evoked potentials are not a good predictor of clinical motor status. The initial morphologic change of these potentials secondary to ischem ia consisted of a decrease in amplitude and in the number of peaks wit hout a shift of latency. Conclusions. The peripheral-NMEP is a better warning system to spinal cord ischemia and its adoption may prevent co rd ischemia during surgery, whereas SEP and spinal-EP can not be indic ies.