Abstract
Measurement of the spinal cord evoked potential as a method for evaluation of spinal cord function has gained increasing importance with the progress of spinal (cord) surgery. A change in the blood flow seems to be closely associated with acute spinal cord injury.
Variation in the spinal cord evoked potentical in relation to a change in the blood flow under application of longitudinal traction was examined using cats. The spinal cord potential was evoked by stimulation of the epidural space (L1 level) from posteriorly and recorded at the epidural posterior region (C2 level) to observe its ascending wave patterns. The intensity of the stimulus was two to three time the threshold value. The blood volume was serially measured by the hydrogen clearance method at the region of the funiculus posterior of the spinal cord. The spinal cord evoked potentical basically consists of two wave patterns. Traction induces a tendency to latency prolongation and also extends the retention of the wave pattern. An increase in the duration of traction augments the wave height in most cases. This is immediately followed by rapid disappearance of the wave. The mean blood volume without traction was 10.3rn1/min/100g. The blood volume was reduced to approximately 50% at the time of transient augmentation of the wave height. The blood flow was not recorded when the wave disappeared.
The changes in the wave of the spinal cord evoked potential were divided into four groups to examine the irreversibility of the change. Transient augmentation was a warning signal Subsequent reduction of the wave height, up to approximately half of the maximun change, seemed to be a reversible change.
