Abstract
This study investigated spinal cord injury affects spinal cord evoked potentials (SCEPs) and spinal cord blood flow.
Twenty-six young mongrel dogs and four monkeys were used. In 13 dogs, transection of the spinal cord was performed in three stages at T12 level and in the other dogs, lateral compression was applied to the spinal cord at T10 level until one of the SCEP amplitudes disappeared. SCEPs induced by transcranial electrical stimulation (TCES) and magnetic stimulation (TCMS) were recorded at T8 and T13 levels using bipolar wire electrodes immediately after the transection or compression. In monkeys, lateral compression was applied at T11 level and SCEPs were recorded at T10 and L1 levels. In dogs, blood flows in the dura mater and in the spinal cord were simultaneously measured using a laser Doppler flowmeter during SCEP measurements.
The results obtained were as follows :
1) In dogs, amplitudes of the second component by TCES and the first component by TCMS significantly decreased immediately after posterior column transection. Anterior column transection resulted in a relatively greater decrease in the amplitude of the first component by TCES. In monkeys, amplitudes of the second component by TCES and the first component by TCMS were higher in the posterolateral column than in other columns. However, the amplitude of the first component by TCES was higher in the anterior column. The latencies of the second component by TCES and the first component by TCMS were similar in both animals. These findings suggest that the second component by TCES and the first component by TCMS would run through a similar tract, probably in the posterolateral column, whereas the first component by TCES would run in the anterior column.
2) Blood flow in the spinal cord was slightly higher than that in the dura mater under preinjury conditions. The spinal cord blood flow (SCBF) temporarily increased after transection and lateral compression of the spinal cord, but the pattern varied in individual animals. This would be due to differences in the spinal blood flow pattern of the animals. SCBF measured cranially to the transection increased more than that measured caudally to the transection of the spinal cord. These findings suggested that the spinal cord would be supplied not only from the segmental radicular arteries, but also from the anterior and posterior spinal arteries.
