Caramia M D, Telera S, Palmieri M G, Wilson-Jones M, Scalise A, Iani C, Giuffrè R, Bernardi G
Clinical Neurology, University of Rome Tor Vergata, Italy.
Neurology. 1998 Jul;51(1):196-202. doi: 10.1212/wnl.51.1.196.
The aim of this study is to provide neurophysiologic evidence of ipsilateral hemispheric activation in patients affected by intracerebral gliomas via the use of transcranial magnetic stimulation.
The mechanisms involved in such ipsilateral activation have yet to be established, but they may involve preexisting routes that either are suppressed or undetected in the normal brain. Ipsilateral pathways may act in reserve, activated by the impairment of contralateral control. This hypothesis is suggested by the fact that the considerable size of the tumors in our patients is not matched by a proportionate loss of motor performance in the limbs contralateral to the affected hemisphere. However, it remains possible that ipsilateral motor-evoked potentials (iMEPs) may reflect reorganizational changes without significant functional effects.
The effects of such activation were investigated using both focal and nonfocal coils stimulating cortical motor areas, with MEPs recorded from both left and right thenar muscles. Fifteen healthy control subjects and seven patients were examined.
iMEPs were generally absent in normal subjects, but in contrast they were obtained in the patients by stimulating the healthy hemisphere using both round and figure-of-eight coils. Distinct from contralateral MEPs, iMEPs are obtained with higher thresholds (range, 60 to 80% of stimulator output) and display longer latencies (20.9 msec versus 19.4 msec).
Taken in conjunction with recent research using functional imaging brain exploration and a variety of clinical, anatomic, and neurophysiologic studies, our results reflect a growing awareness of ipsilateral motor control and its potential compensatory role when contralateral routes are damaged.
本研究旨在通过经颅磁刺激，为脑内胶质瘤患者同侧半球激活提供神经生理学证据。
这种同侧激活所涉及的机制尚未明确，但可能涉及在正常大脑中被抑制或未被检测到的既有通路。同侧通路可能作为备用途径，在对侧控制受损时被激活。这一假设的依据是，我们患者的肿瘤体积相当大，但患侧半球对侧肢体的运动功能丧失程度却与之不成比例。然而，同侧运动诱发电位（iMEP）仍有可能反映的是重组变化，而无显著功能影响。
使用聚焦和非聚焦线圈刺激皮质运动区，记录左右大鱼际肌的运动诱发电位，以研究这种激活的效果。对15名健康对照者和7名患者进行了检查。
正常受试者一般不存在iMEP，但与之相反，在患者中，使用圆形和8字形线圈刺激健康半球时均能记录到iMEP。与对侧运动诱发电位不同，iMEP的获得阈值更高（范围为刺激器输出的60%至80%），且潜伏期更长（20.9毫秒对19.4毫秒）。
结合近期使用功能性脑成像探索以及各种临床、解剖学和神经生理学研究的成果，我们的结果反映出人们越来越意识到同侧运动控制及其在对侧通路受损时的潜在代偿作用。
