Changes of somatosensory function by low frequency transcranial magnetic stimulation over the motor cortex

目的：研究重复经颅磁刺激(RTMS)对人体运动皮质电流知觉阈值(CPT)的影响。实验11.实验对象与方法：对10名健康受试者(男5名，女5名；平均年龄35.8±5.7)进行右侧运动皮质0.9 Hz重复经颅磁刺激及假刺激。RTMS强度固定在运动皮质手部静息运动阈值的90%。每名受试者都被给予500次刺激。用Neurotoron(马里兰州巴尔的摩，Neurotoron)的Neuroeter^&lt；TM&gt；测定rTM前、后左食指CPT(2k、250、5 Hz)。结果：rTMS后运动皮质2k和5 Hz的CPT均显著增加，但均在正常范围内。假刺激或感觉皮质上的rTMS对CPT没有影响。对象和方法：研究对象为左额顶叶脑挫伤的56岁女性，年龄51岁。她有右侧偏瘫，没有感觉减退和痛觉减退。在与健康受试者相同的条件下，对左侧运动皮质进行rTMS。分别于rTM前、后测定右手食指CPT(2k和5 Hz)。结论2 kHzCPT与Aβ纤维阈值有关，5 HzCPT为C纤维，它们分别与触觉和慢性疼痛有关。实验一表明，rTMS同时提高了健康志愿者的触觉感觉阈值和缓慢痛觉阈值。但仍在正常范围内，这一结果提示rTM的安全性。在实验2中，由于病例有限，尚不清楚结果是否反映了目前所有脑损伤患者的趋势。

Objective : To study changes of current perception threshold (CPT) by repetitive transcranial magnetic stimulation (rTMS) over the motor cortex in humans.Experiment 11. Subjects and Methods : 0.9Hz rTMS over the right motor cortex, sensory cortex and sham stimulation were given to ten healthy subjects (five men and five women ; mean age ± SD, 35.8 ± 5.7). The intensity of rTMS was fixed at 90% of the resting motor threshold at the hand area of motor cortex. 500 stimuli were given in each subject. CPTs (2k, 250, 5 Hz) of the left index finger were determined by using Neurometer^<TM> (Neurotoron, Baltimore, MD), before and after rTMS.2. Results : The CPTs of 2k and 5 Hz were significantly increased after rTMS over the motor cortex, but the changes were within normal limits. Sham stimulation or rTMS over the sensory cortex had no effect on CPTs.Experiment 21. Subjects and Methods : 56-year-old woman with a brain contusion of left fronto- parietal lobe at the age of 51 was the subject. She had right hemiparesis without hypesthesia and hypalgesia. rTMS was given over the left motor cortex in the same condition as the healthy subjects. CPTs (2k and 5 Hz) of the right index finger were determined before and after rTMS.2. Results : CPTs of 2k Hz as well as 5 Hz were decreased.Conclusions2kHz CPT is related to the threshold of Aβ-fiber, and 5Hz CPT is C fiber, and they are involved in tactile sensation and a slow pain respectively. Experiment 1 suggests that rTMS increased the threshold of tactile sensation and a slow pain in a healthy volunteer at the same time. But it remains a within normal limits, and this result suggests to that of the safety of rTMS.At experiment 2, because of limited case, it is unclear whether the result indicates the tendency all patients with brain damage at this moment.