MONITORING OF EVOKED-POTENTIALS DURING SPINAL-CORD ISCHEMIA - EXPERIMENTAL EVALUATION IN A RABBIT MODEL

Objectives: somatosensory evoked potentials (SEPs), spinal evoked pote ntials (Spinal-EPs), and motor-evoked potentials (MEPs) were monitored in a rabbit model of spinal cord ischaemia to evaluate their accuracy and relationship to clinical status. Methods: a modified rabbit spina l cord ischaemia model of infrarenal aortic occlusion for 21 min was e mployed (30 rabbits). After baseline SEPs, Spinal-EPs, and MEPs were o btained, evoked potentials were recorded continuously during and after clamping of the aorta (30 min). Neurological outcome at 24h was corre lated with evoked potentials, and histopathological findings. Results: fifteen animals became paraplegic. Meps were always abolished after c lamping of the aorta while Spinal-Eps and SEPs remained. The sensory e voked potentials (SEPs and Spinal-EPs) were the least sensitive to spi nal cord ischaemia, and their presence had no correlation with the fin al clinical status (50% of false negatives). This was consistent with histopathological examination that showed damage almost entirely confi ned to the anterior horn, while the dorsal columns were generally well preserved. High spine MEPs evoked by twitch stimulation was the best predictor of clinical outcome (0% of false negatives, 0% of false posi tives). Conclusions: SEPs and Spinal-EPs cannot be used as safe monito rs of ischaemia of the spinal cord. High spine MEPs evoked by twitch s timulation was the most useful for real-time evaluation of spinal cord ischaemia, and the best predictor of neurologic outcome during reperf usion.