Motor evoked potentials(MEPs) and somatosensory evoked potentials(SSEPs) have been used to evaluate the integrity of ascending and descending pathways in the spinal cord, and assess pathways involved in spinal cord injury. The purpose of this
study
was
to evaluate the changes of MEPs elicited by transcranial electrical stimulation following acute spinal cord injury in Sprague-Dawley rats. MEPs were evoked by electrical stimulation of the right somatic motor cortex through a stainless steel
screw
and
recorded epidurally at T8 and L1 spinal cord levels using two pairs of teflon-coated stainless steel wire electrodes with 1mm exposed tip. Thirty animals received a 12.5g/cm(n=10), 25g/cm(n=10). 75g/cm(n=10) weight drop injury at T10 spinal cord
level
and other 5 animals severed as a ventral or dorsal cord transection.
The normal MEPs were composed of reproducible 4 waves, such as P1, P2, P3, and P4. The conduction velocities of P1, P2, P3, P4 were 60, 45, 37, 25m/sec, respectively. The ventral cord section produced complete loss of MEPs, whereas the dorsal
cord
section showed minimal change of MEPs. The 75g/cm drop injury abolished all MEP waves distal to the lesion and the MEPs did not appear till 3 hours after injury. Decrement of amplitude and shift of latency of MEPs following 25g/cm drop injury
were
greater than those in MEPs following 12.5gm/cm drop injury. The MEPs following 12.5g/cm drop injury recovered by 60 min, and duration of recovery in 25g/cm drop injury was longer than in 12.5g/cm drop injury.
These results suggest that the ventral descending tracts may play a major role in the spinal conduction pathway of MEPs in rats and MEPs will be a useful method of the assessment of severity in spinal cord injury.
|