Study of neuronal plasticity in children by biomagnetism

神经元可塑性是指损伤的神经元将会恢复和/或某个脑环区域将包含其他功能。这种可塑性将在未成熟的大脑中发生得更加戏剧性。本项目的目的是确定儿童时期受损大脑的功能，以及大脑原始区域以外的某些区域是否具有功能。应用脑磁图(MEG)对皮质发育不良患者的脑功能分布进行了研究，其中局灶性皮质发育不良2例，带状异位2例，半脑大脑和脑室周围结节异位各1例，半球皮质发育不良2例，皮质发育不良3例。11例中有6例根据SEF的信号源识别出中央沟，其中4例N20m的潜伏期、波幅和方向均异常。电流方向的异常提示在神经元移行期神经元的形态发生了扭曲。在迁徙障碍的情况下，电生理参数表现出不同的变化。这种异质性很可能是由于移行期神经元排列的扭曲所致。大脑半球皮质发育不良伴脑回和脑沟异常模式患者癫痫活动的信号源分析。2例患者的大脑半球有癫痫活动。在一个病例中，在未受影响的大脑半球也观察到了另一种癫痫活动，其中EEG无法检测到癫痫放电。脑磁图在检测稀有癫痫活动方面具有优势。

Neuronal plasticity is that the damage to the neuron will recover and/or a cirtain brain region will contain other function. The plasticity will occur more dramatically in immature brain. The purpose of this project is to determine the function of injured brain in childhood and whether some area of the brain other than original region possess functioning. We evaluated the distribution of the brain function in cortical dysplasias using magnetoencephalography (MEG).The subjects included 2 cases of focal cortical dysplasia, 2 cases of band heterotopia, each one case of hemimegalencephaly and periventricular nodular heterotopia, 2 cases of hemispheric cortical dysplasia, and other 3 cases of cartical displasia, Sensory evoked fields (SEF) induced by left and right median nerve stimulation were recorded in a magnetically shielded room using a 122-channel whole head MEG system (Neuromag-122, Neuromag Ltd.)The central sulci were identified according to the signal sourse of SEF in 6 out of the 11 cases cortical dysplasia and abnormal patterm of gyri around the central sulcus.In the 4 cases, the latency, amplitude and direction of the electric current of N20m showed abnormal. The abnormal direction of the electric current implies that the fomation of neurons were distorted during neuronal migration period. In cases of migration disorders, the electrophysiological parameters show variable changes. This heterogeueity is likely due to distortion of neuronal arrangement during migrating period.Signal sourse analysis of epileptic activity in cases of hemispheric cortical dysplasia with abnormal pattern of gyri and sulci decreased volume in the affected side. Epileptic activity was found in the affected hemisphere in 2 cases. In one case, another epileptic activity was also observed in the non-affected hemisphere in which EEG could not detected epileptic discharges. The MEG has superiority for detection of scarce epileptic activity.