外周神经损伤后大脑运动皮层局部调整的功能磁共振研究

目的利用功能磁共振方法观察全臂丛神经损伤以后,大脑初级运动皮层的动态变化,探讨可能的机理。方法经临床检查和手术证实全臂丛神经损伤患者5例,4例接受了神经移位术,以部分恢复肘关节和肩关节功能。按照患者在手术治疗前是否接受过MR检查,将患者分为2组：A组手术治疗前接受fMRI检查者4例(例1、3、4、5),B组手术治疗以后接受fMRI随访复查者4例(例2、3、4、5)。fMRI检查采用血氧饱和依赖(BOLD)方法,运动任务包括双侧手部的简单的对掌运动,患侧手部运动要求在“模拟”状态下完成。然后记录激活区兴奋像素大小和出现部位,观察信号强度。单个受检者以健侧肢体运动时大脑皮层激活区为参照,进行一对一比较。对A和B两组病例则以正常志愿者观察结果为参照,进行组与组之间比较。结果健侧手部运动均在对侧大脑半球产生较强烈的信号变化。A组患者中,当患手模拟“运动”时,2例在对侧初级运动皮层观察到分散、点状兴奋区,信号强度比健手代表区信号强度明显减弱,另2例未见激活区出现,所有病例均有辅助运动区神经活动。B组患者中,随着时间延长,患肢对侧初级运动皮层出现激活区并且呈现逐渐增大趋势。结论外周神经损伤后,初级运动皮层可以发生显著变化,功能磁共振是一种评价外周神经损伤以后运动皮层可塑性变化的有效的无创伤性方法。

Regional modulation of primary motor cortex after peripheral nerve injury: a functional magnetic resonance imaging study

OBJECTIVE: To map dynamic changes of primary motor cortex after total brachial plexus traction injury by using functional magnetic resonance imaging, and to explore underlying probable mechanisms. METHODS: Five patients with total traumatic root avulsions of the brachial plexus underwent varied kinds of nerve transfer to restore partially shoulder or elbow function. Four of them (cases 1, 3, 4, 5) accepted the first fMRI examination prior to surgery treatment, and four of them (cases 2, 3, 4, 5) accepted second or third or fourth fMRI follow-up re-examinations after surgery treatment. Maps of neuronal activation within the motor cortex were generated for both hands in each patient by using BOLD-fMRI and the cluster size and position were recorded. The motor tasks consisted of simple hand grasping of both hands respectively. Patients with paralytic hand were asked to complete task under "virtual" condition. The cluster size and intensity as well as location of motor activation within the primary motor cortex of the affected hand generated were compared with those of unaffected hand generated as reference in single subject, and the resultant maps of follow-up re-examinations were also compared with those of the prior examinations. RESULTS: All patients' unaffected hand movement generated strong signal change within the contralateral primary motor cortex. In contrast, the clusters generated by affected hand showed very small and lower intensity than usual (2 cases) or could not be induced (2 case) in the first examination that prior to surgery treatment and seemed larger gradually in the following re-examination with time increasing. CONCLUSION: Peripheral nerve injury can produced significant changes in the motor cortex of human brain. fMRI is a valuable tool to evaluate neural plasticity in motor cortex after peripheral nerve injury.