Effects of epidural electrical stimulation modalities on spinal cord function and morphology in cats.

The safety of direct electrical stimulation to the spinal cord as used in spinal cord monitoring is controversial. This investigation was undertaken to determine the critical condition of continuous electrical stimulation over a period of 30 min with varying intensities and pulse durations, and the level of safety of intermittent stimulation of 100 pulses with 10 mA current of 0.3 msec duration with varying resting intervals. The spinal cord was evaluated by spinal cord evoked potentials (SCEP) recording and histological examination. The intensity of continuous stimulation greater than 10 mA of 0.3 msec duration resulted in permanent changes in SCEP, focal colliquative necrosis of the cord, and acceleration of the permeability of the intrinsic vessels. In the intermittent stimulation with 1-min resting intervals, spinal cord lesions were not observed.