[Experimental and clinical studies of the evoked electrospinogram for monitoring spinal cord function (author's...

The evoked electrospinograms (EESG), by stimulation of and recording from the spinal cord, was investigated as a means of estimating spinal cord function and damage. Sixteen mongrel adult dogs were monitored in a basic examination of EESG. Relationship between change of EESG and spinal cord function was examined in 27 dogs. A spinal compression device was placed at L2 level, and bipolar electrodes at the T11 and L5 levels respectively. Supramaximal electric stimulation with rectangular pulses of 0.1 millisecond and 2 to 5 volt was given once per second by constant current stimulation. EESGs were classified according to the change in amplitude caused by acute spinal cord compression and were observed for three weeks. Results 1. Spike potentials in short latency of EESG were interpreted as action potentials which directly pass through superficial layer of posterolateral tracts of spinal cord, and change of spike potentials were through not to reflect the histological degeneration of gray matter and one side of the spinal cord. 2. Spike potentials on acute spinal cord compression showed temporary increase of amplitude followed by reduction of amplitude with increasing latency, finally disappearance. Decrease of amplitude of spike potentials was noted initially at the compression which narrowed spinal canal diameter about 5%. Disappearance of spike potentials took place suddenly at the compression causing 80% narrowing of spinal canal diameter. 3. Change of spike potentials by acute spinal cord compression corresponded well to the prognosis of motor function. Voluntary motor function may be estimated subjectively by change of amplitude of spike potentials of EESG. Namely, in dogs with decrease of the amplitude by half, a full recovery of hind-limb paralysis took place. In 1/3 of the dogs with decrease of the amplitude of more than half, incomplete paralysis persisted, and disappearance of the potential indicated of severe paralysis. Based on the data from the above experiments, EESGs induced from 40 clinical cases were analyzed. Conclusions. This study showed that EESG by stimulation of the spinal cord was an effective method in spinal cord monitoring. However, the clinical data showed no distinct correlation between EESG and the degree of spinal cord function as did the animal experiments.