SENSORY EVOKED-POTENTIALS FOR SELECTIVE MONITORING OF THE RAT SPINAL-CORD - A CEREBELLAR EVOKED-POTENTIAL TO ASSESS VENTRAL CORD INTEGRITY

The purpose of this study was to evaluate two types of ascending senso ry evoked potentials (SEPs) in the rat and their capacity for selectiv e monitoring of dorsal versus ventral spinal cord integrity. SEPs were elicited by direct sciatic nerve stimulation. A cerebellar evoked res ponse was recorded over the paramedian lobule of the cerebellar hemisp here (CEP(pml)) while somatosensory evoked potentials (SSEPs) were sim ultaneously recorded over the sensorimotor cortex. All components of t he CEP(pml) and SSEP except the longest latency positive waves were pr esent in each animal. At stimulus intensities of 3 to 10 mA, no signif icant changes in latency of the peaks were observed, but amplitudes of the longer latency responses tended to increase throughout this stimu lation range. Unilateral sciatic stimulation resulted in bilateral cor tical responses, larger ipsilaterally for the CEP(pml), and contralate rally for the SSEP. Selective spinal cord lesions demonstrated N9 and P14 of the CEP(pml) to be mediated primarily through the ventral spina l cord, while P14 and N19 of the SSEP were conducted primarily through the dorsal columns. Sectioning of the cerebellar peduncles abolished N9 and P14 of the CEP(pml) despite persistence of the SSEP. This study demonstrates that selective assessment of the ventral and dorsal spin al cord is possible in the rat by monitoring SEPs.