SPINAL-CORD MONITORING OF THE VENTRAL FUNICULUS FUNCTION - ANALYSIS OF SPINAL FIELD POTENTIALS AFTER GALVANIC VESTIBULAR STIMULATION

Study Design. this study was designed to examine the possibility of a new spinal cord monitoring method using galvanic vestibular stimulation to monitor the function of the ventral funiculus of the spinal cord. Objectives. To settle the problems of previous monitoring methods by using galvanic vestibular nerve stimulation, which is highly selective for monitoring the function of the ventral funiculus of the spinal cord. Summary of Background Data. Although various spinal cord monitoring methods have been used, there are still problems because potentials recorded by these methods do not reflect selectively the function of the ventral funiculus of the spinal cord, which is vulnerable during anterior spinal surgeries. Methods. In anesthetized cats, field potentials evoked by galvanic stimulation of the labyrinth were recorded from the epidural space of the spinal cord. The origin of these potentials was determined by mapping field potentials from within the upper cervical spinal cord using a micropipette and by examining the effect of sectioning the brainstem on the evoked potentials. Results. The spinal cord potentials evoked by galvanic stimulation between the bilateral labyrinths could be recorded from the epidural space, and these potentials mainly originated from the ventral and ventromedial funiculus of the spinal cord. The latency and intraspinal distribution of the evoked potentials and the effect of sectioning the medial longitudinal fascicle on the evoked potentials indicated that the earliest component of the evoked potentials reflects mainly the activity of the vestibulospinal tract. Conclusions. Recording spinal cord potentials evoked by galvanic vestibular stimulation from the epidural space appears to be a potential technique to monitor the functional state of the ventral funiculus during anterior spinal surgeries.