Tsuji S, Lüders H, Dinner D S, Lesser R P, Klem G
Electroencephalogr Clin Neurophysiol. 1984 Jun;59(3):229-37. doi: 10.1016/0168-5597(84)90062-5.
The effects of stimulus intensity on subcortical and cortical somatosensory evoked potentials (SEPs) to posterior tibial nerve (PTN) stimulation were studied in 16 normal controls. Stimulus intensity was evaluated as a function of sensory threshold (S). Motor threshold (M) varied between 1 S and 2 S. The amplitude of N18 (afferent volley immediately before it enters the spinal canal) increased approximately linearly up to at least 4.5 S. N20 (dorsal cord potential) also demonstrated a linear increase up to at least 4 S but the rate of increase was significantly smaller. All central components (subcortical brain-stem components P27 and N30, and cortical components N1 and P2) showed an even smaller rate of increase which was non-linear and reached a plateau at 3 S. The relatively higher rate of increase of N18 as compared with N20 was most probably due to the recording of sensory impulses plus antidromic impulses in motor fibers. The smaller rate of increase and early saturation of all the central components compared with N20 suggests that of all the afferent fibers generating N20 only the low threshold fibers participate in the generation of more central components. Stimulus intensities of 3 S are recommended for clinical studies of the central SEPs to PTN stimulation.
在16名正常对照者中研究了刺激强度对胫后神经（PTN）刺激引起的皮层下和皮层体感诱发电位（SEP）的影响。刺激强度根据感觉阈值（S）进行评估。运动阈值（M）在1S至2S之间变化。N18（传入冲动进入椎管之前的传入波群）的波幅至少在4.5S之前近似呈线性增加。N20（脊髓背侧电位）在至少4S之前也呈线性增加，但增加速率明显较小。所有中枢成分（皮层下脑干成分P27和N30以及皮层成分N1和P2）的增加速率更小，呈非线性，在3S时达到平台期。与N20相比，N18相对较高的增加速率很可能是由于记录了感觉冲动以及运动纤维中的逆行冲动。与N20相比，所有中枢成分的较小增加速率和早期饱和表明，在产生N20的所有传入纤维中，只有低阈值纤维参与了更多中枢成分的产生。建议在对PTN刺激的中枢SEP进行临床研究时采用3S的刺激强度。
