急性枕叶脑梗死患者视觉皮质中枢脑磁图变化特征

目的研究急性枕叶脑梗死患者视觉皮层中枢脑磁图(MEG)的变化特征。方法对6例急性单侧枕叶梗死表现为对侧视野同向偏盲患者于发病后2周内行视觉诱发磁场(VEFs)测试,并检测8名健康志愿者作为正常对照。刺激选取黑白棋盘格翻转图形。分别记录两组受试者VEFs的M100波峰产生的潜伏期、波形、等电流偶极(ECD)强度和磁源性影像(MSI)。结果所有受试者VEFs反应的最基本波形为M100,位于距状裂两侧的皮质。与正常对照组相比,患者健侧枕叶的VEFs反应波形,潜伏期和ECD强度并无明显差异(均P>0.05),而患侧枕叶的VEF反应则出现了波形异常,潜伏期明显延长和ECD强度显著降低(均P<0.05)异常,且MSI显示其M100反应的ECD位置分布紊乱。结论MEG可检测出急性枕叶脑梗死患者视觉皮质中枢功能的损伤,并能够客观的评价患者视觉皮层中枢的功能状态。

Clinical study of the visual evoked fields in patients with acute occipital lobe infarction by magnetoencephalography

Objective To investigate the characteristics of visual evoked fields(VEFs)in patients with acute occipital lobe cerebral infarction by magnetoencephalgraphy(MEG).Methods VEFs were observed using 306-channel whole-head MEG 6 in patients with acute unilateral occipital lobe cerebral infarction who showed homonymous hemianopia.Eight healthy volunteers were used as controls.In the task,all participants were given pattern reversal stimuli of vertical half fields and quadrant fields of both eyes.The interstimulus interval was 2 minutes.The peak latency,waveform,and strength of equivalent current dipole(ECD)of the VEFs M100 were recorded.The M100 ECD positions in the two hemispheres were also examined,which were superimposed on MRI to produce a magnetic source imaging(MSI).Results M100 was the most elemental component of VEFs in all subjects,originating from the area around the calcarine sulcus.The activities of VEFs in the unaffected hemispheric occipital lobe in the patient group were not different from those in the control group.However,abnormal VEFs M100 activities occurred in the affected occipital lobe of the patient group,including abnormal waveforms,prolonged peak latency,decreased strength of ECD and irregular distribution of ECD in MSI.Conclusions Latent cortical impairment may be evaluated by MEG.MEG may provide objective and sensitive indexes for the evaluation of function of visual cortex in patients with acute occipital lobe cerebral infarction.