To explore the sensitivity of transcranial electrical stimulation motor evoked potential (TceMEP) after acute sciatic nerve root injury in rabbits and the evaluation value of its early waveform changes after acute sciatic nerve root injury.

Twelve New Zealand rabbits with 24 sciatic nerves were divided into 3 groups by random grouping method, one vascular clamping group (n=8), two vascular clamping groups (n=8) and the control group (n=8). The acute sciatic nerve injury model was established by using one or two vascular clamp compression of the sciatic nerve root, the TceMEP was recorded for 2 hours to observe the characteristics of TceMEP in the acute phase of sciatic nerve root compression injury, the percentage of TceMEP amplitude of stabilized waveform after compression injury to baseline amplitude and latency were recorded. The control group was used to exclude the effects of anesthetic and surgical operations on TceMEP. The lower limb motor function was evaluated using the Tarlov score after 2 days of clamping. Statistical analysis was performed using t-test, one-way ANOVA, rank sum test and spearman correlation analysis.

TceMEP waveform of 1 vascular clamping group was changed at [0.20(0.00, 0.43)]min and was stable at [2.60(1.40, 3.35)]min; TceMEP waveform of 2 vascular clamping group was changed at [(0.35(0.05, 1.63)]min and was stable at [4.45(2.83, 5.65)]min. The percentage of postoperative amplitude when the waveform was stable to baseline in 1 and 2 vascular clamping group [(49.84±15.27)%, (15.47±12.64)%] were lower than the percentage of preoperative amplitude [(100.00±0.00)%, (100.00±0.00)%], there were statistically significant differences (t=9.293, 18.912, all P<0.01). There was statistically significant difference between the control group and the experimental groups in the percentage of postoperative amplitude when the waveform was stable to baseline (F=110.196, P<0.05). The postoperative latency when the waveform was stable in 1 and 2 vascular clamping groups [(12.60±0.61)ms, (14.29±1.24) ms] were higher than the preoperative latency [(12.21±0.59)ms, (12.31±1.10)ms], there were statistically significant differences (t=7.519, 5.721, all P<0.05). There was statistically significant difference of the postoprative latency in the control group and the experimental groups (F=6.702, P<0.05). The lower limb motor function scores after 2 days of clamping in 1 and 2 vascular clamping groups [4.00(3.00, 4.00), 2.50(2.00, 3.00)] were lower than the control group [5.00(5.00, 5.00)], there were statistically significant differences (Z=-3.664, -3.651, all P<0.05), which were also lower than the motor function scores before clamping [5.00(5.00, 5.00), 5.00(5.00, 5.00)], there were statistically significant differences (Z=-2.598, -2.585, all P<0.05). The percentage of postoperative amplitude when the waveform was stable to baseline and the Tarlov motor function scores after 2 days of clamping were significantly positively correlated in the control group and experimental groups (r=0.844, P<0.01).

TceMEP monitoring is very sensitive to the detection of acute sciatic nerve root injury, which is manifested as prolonged latency and decreased ampilitude, it provides the possibility of taking protective measures to prevent the occurrence of irreversible nerve root injury. The motor function of lower limbs can be predicted by the change of TceMEP waveform.