Gilio Francesca, Suppa Antonio, Bologna Matteo, Lorenzano Cinzia, Fabbrini Giovanni, Berardelli Alfredo
Department of Neurological Sciences and Neuromed Institute (IRCCS), University of Rome "La Sapienza", Rome, Italy.
Mov Disord. 2007 Jul 30;22(10):1436-1443. doi: 10.1002/mds.21465.
Repetitive transcranial magnetic stimulation (rTMS) delivered at 5 Hz frequency and suprathreshold (RMT) intensity produces a progressive facilitation of motor-evoked potential (MEP) amplitude that outlasts the end of stimulation. This phenomenon is related to a short-term enhancement of cortical excitatory interneurones. In this study, we investigated whether 5 Hz-rTMS elicits similar MEP facilitation during stimulation and similar facilitatory after-effects in patients with upper limb dystonia and healthy subjects. Trains of 5, 10, and 20 stimuli were delivered at 120% RMT over the primary motor cortex with the subjects at rest. rTMS-trains were followed by single test stimuli delivered at various interstimulus intervals (0.5-10 s) at 120% RMT using a conditioning-test paradigm. Single conditioning stimuli were also delivered. The effects of suprathreshold 1 Hz-rTMS were also tested. The MEP amplitude during the course of the trains and of the test stimuli was measured. In control experiments, we investigated the role of the afferent inputs elicited by muscle twitches after ulnar nerve stimulation on the MEP amplitude. In patients and healthy subjects, MEP amplitude increased significantly during the course of 5 Hz-trains. In both groups the MEP facilitation outlasted the end of 5 Hz-rTMS, however the facilitatory after-effects were more pronounced and lasted longer in patients than in healthy subjects. MEP amplitudes during and after 1 Hz-rTMS remained unchanged. Ulnar nerve stimulation did not change the test MEP amplitude. We conclude that in patients with upper limb dystonia there is an abnormal recovery from MEP facilitation after suprathreshold 5 Hz-rTMS suggesting an abnormal pattern of short-term cortical plasticity.
以5赫兹频率和阈上（静息运动阈值，RMT）强度进行的重复经颅磁刺激（rTMS）会使运动诱发电位（MEP）的幅度逐渐增大，且这种增大在刺激结束后仍会持续。这种现象与皮质兴奋性中间神经元的短期增强有关。在本研究中，我们调查了5赫兹rTMS在刺激期间是否会在患有上肢肌张力障碍的患者和健康受试者中引发类似的MEP增强，以及是否会产生类似的促进后效应。在受试者休息时，以120%RMT的强度在初级运动皮层上施加5次、10次和20次刺激的序列。rTMS序列之后，使用条件-测试范式，以120%RMT的强度在不同的刺激间隔（0.5 - 10秒）施加单次测试刺激。也施加了单次条件刺激。还测试了阈上1赫兹rTMS的效果。测量了刺激序列和测试刺激过程中的MEP幅度。在对照实验中，我们研究了尺神经刺激后肌肉抽搐引发的传入输入对MEP幅度的作用。在患者和健康受试者中，5赫兹刺激序列期间MEP幅度显著增加。在两组中，MEP促进在5赫兹rTMS结束后仍持续存在，然而，患者的促进后效应比健康受试者更明显且持续时间更长。1赫兹rTMS期间及之后的MEP幅度保持不变。尺神经刺激未改变测试MEP幅度。我们得出结论，在上肢肌张力障碍患者中，阈上5赫兹rTMS后MEP促进的恢复存在异常，这表明短期皮质可塑性模式异常。
