EFFECTS OF SQUARE-PULSE STIMULATION ON FUNCTIONAL RECOVERY FOLLOWING A CRUSH INJURY TO THE SCIATIC NERVE IN RATS

Yoo, Seog Keun

Abstract

Effects of square-pulse stimulation on the functional recovery following a nerve injury were examined in rats. a crush injury was made on the sciatic nerve under ketamine anesthesia and square-pulse stimulation with 5 - 7 V, 0.2 ms, 20 Hz, and 5 sec ON-OFF type was applied to the lesion site through teflon coated stainless steel wires(0.45mm in diameter) for 4 hours per day up to 2 days. Motor evoked potential(MEP) of the tibial nerve and somatosensory evoked potential (SSEP) of the T12 spinal cord were recorded. And their threshold, amplitude and latency were then analyzed. 1. Threshold of MEP was 41+/-5 uA, and that of SSEP was 39+/-13 uA. 2. MEP was composed of 3 waves, i.e., N1, N2, N3, in which Nl was conducted by A alpha fibers and the others by the synaptic fibers from the spinal cord. 3. SSEP was also composed of 3 waves, in which N1 was conducted by IA, N2 to II, and to III fibers. 4. MEP and SSEP were abolished immediately after crush injury and SEsP was more sensitive, N1 disappeared faster than N2 and N3. 5. Evoked potentials were abolished by application of local anesthetics, in which N2 and N3 were more sensitive than Nl. 6. Electrical stimulation decreased thresholds evoked potentials down to 50% in MEP, and 30% in SSEP. 7. Electrical stimulation increased amplitudes of evoked potentials and decreased latencies following the injury. These results suggest that square-pulse stimulation is effective in promoting the functional recovery following a nerve injury, Study of MEP and SSEP may be useful parameters to evaluate the nerve function following an injury.