Objective: To better understand the characteristics of the neurogenic motor evoked potential (NMEP) before and after acute spinal cord injury. Methods: We recorded and characterized the spinal cord NMEP from 48 normal...Objective: To better understand the characteristics of the neurogenic motor evoked potential (NMEP) before and after acute spinal cord injury. Methods: We recorded and characterized the spinal cord NMEP from 48 normal rats and from 38 rats with spinal cord hemisection lesion. Spinal cord NMEPs were elicited by applying a range of current intensities with bipolar microelectrode stimuli to the C4 cord segment and recording the responses from sciatic nerves with bipolar microelectrodes placed in the neurilemma. Results: The evoked potentials consisted of three stable and reproducible negative and three positive peaks. The mean ±SD latencies of N1 were 2.89 ± 0.22 ms on the right side and 2.89 ± 0.24 ms on the left side. The mean conduction velocity was 47.9 m/s. The mean ±SD amplitudes of N1 were 3.61 ± 2.10 μV on the right side and 3.83 ± 2.32 μV on the left side. The amplitudes of N1 were significantly different among the eight stimulus intensity groups (right side: F= 2.22 , df= 7?201 , P= 0.03 ; left side: F= 2.11 , df=7?206, P= 0.04 ). The amplitude was largest when the stimulus intensity was 1.1 2.5 mA. The latencies of N1 were not significantly different among the eight stimulus intensity groups (right side: F= 0.40 , df= 7?201 , P= 0.9 ; left side: F= 1.20 , df=7?206, P= 0.3 ). The amplitudes and latencies of N2, N3 were not significantly different among the eight stimulus intensity groups. There were no significant changes in latency and amplitude between the left and the right side nerve responses. Thirty eight rats underwent T9 cord right side hemisection. Among them, 20 (53%), 30 (79%), and 32 (84%) rats could not be recorded in corresponding to N1, N2, and N3, respectively, in the right side sciatic nerves; and 13 (79%), 18 (47%), and 21 (55%), in corresponding to N1, N2, and N3 in the left side sciatic nerves. The latency was significantly delayed on the both right and left sides. The amplitude N1 was significantly depressed on the both sides, with N3 significantly depressed on the right side and N2 not significantly depressed. Conclusions: The amplitude of N is significantly different among the eight stimulus intensity groups. The amplitude is largest when the stimulus intensity is 1.1 2.5 mA. The light injury results in a significant latency delay in N1, N2, and N3 waves and a significant amplitude attenuation in N1. The N1 amplitude is sensitive to the degree of the lesion and conducts bilaterally. N2 and N3 conduct mainly along the ipsilateral posterolaterial tracts in the rats.展开更多
文摘Objective: To better understand the characteristics of the neurogenic motor evoked potential (NMEP) before and after acute spinal cord injury. Methods: We recorded and characterized the spinal cord NMEP from 48 normal rats and from 38 rats with spinal cord hemisection lesion. Spinal cord NMEPs were elicited by applying a range of current intensities with bipolar microelectrode stimuli to the C4 cord segment and recording the responses from sciatic nerves with bipolar microelectrodes placed in the neurilemma. Results: The evoked potentials consisted of three stable and reproducible negative and three positive peaks. The mean ±SD latencies of N1 were 2.89 ± 0.22 ms on the right side and 2.89 ± 0.24 ms on the left side. The mean conduction velocity was 47.9 m/s. The mean ±SD amplitudes of N1 were 3.61 ± 2.10 μV on the right side and 3.83 ± 2.32 μV on the left side. The amplitudes of N1 were significantly different among the eight stimulus intensity groups (right side: F= 2.22 , df= 7?201 , P= 0.03 ; left side: F= 2.11 , df=7?206, P= 0.04 ). The amplitude was largest when the stimulus intensity was 1.1 2.5 mA. The latencies of N1 were not significantly different among the eight stimulus intensity groups (right side: F= 0.40 , df= 7?201 , P= 0.9 ; left side: F= 1.20 , df=7?206, P= 0.3 ). The amplitudes and latencies of N2, N3 were not significantly different among the eight stimulus intensity groups. There were no significant changes in latency and amplitude between the left and the right side nerve responses. Thirty eight rats underwent T9 cord right side hemisection. Among them, 20 (53%), 30 (79%), and 32 (84%) rats could not be recorded in corresponding to N1, N2, and N3, respectively, in the right side sciatic nerves; and 13 (79%), 18 (47%), and 21 (55%), in corresponding to N1, N2, and N3 in the left side sciatic nerves. The latency was significantly delayed on the both right and left sides. The amplitude N1 was significantly depressed on the both sides, with N3 significantly depressed on the right side and N2 not significantly depressed. Conclusions: The amplitude of N is significantly different among the eight stimulus intensity groups. The amplitude is largest when the stimulus intensity is 1.1 2.5 mA. The light injury results in a significant latency delay in N1, N2, and N3 waves and a significant amplitude attenuation in N1. The N1 amplitude is sensitive to the degree of the lesion and conducts bilaterally. N2 and N3 conduct mainly along the ipsilateral posterolaterial tracts in the rats.
