Functional MRI of the visual cortex in the infants with perinatal brain damage

目的：对脑室周围白质软化症(PVL)患儿进行视刺激功能磁共振成像(FMRI)检查，探讨其与视功能、MR异常及视激活模式的相关性。方法：对8例出生后6个月内经MRI诊断为PVL的患儿和8例无PVL患儿(对照组)在1.5T磁共振系统上进行多层回波平面fMRI检查。所有婴儿均静脉注射戊巴比妥钠3~5 mg/kg。连续采集100组梯度回波平面数据，TR/TE为3000/50，翻转角为90，视野为220，图像矩阵为128×128，层厚为5 mm。每个数据集包含连续的3个覆盖钙化骨沟的轴位切片。最初的静息基线阶段为30秒，然后是光刺激阶段和休息阶段交替进行，每次试验总共10个阶段。结果：8例无PVL的婴幼儿在接受视觉刺激时，视皮质信号减弱。另一方面，在8例PVL婴儿中，有6例在视皮层没有表现出激活。这6名婴儿在出生后6个月时出现严重斜视，不能跟随物体。他们在两岁时都有严重的脑瘫和智力低下。提示脑功能磁共振成像是评价婴幼儿视功能的一种有效方法。

Purpose : Functional MRI (fMRI) with visual stimulation was evaluated in infants with periventricular leukomalacia (PVL), in order to examine the correlation of visual function, MR abnormalities and visual activation patterns.Methods: 8 infants with PVL diagnosed with MRI within 6 months after birth and 8 infants without PVL (control group) were examined with multislice echoplanar fMRI on a 1 .5T MR -system. All infants were Intravenously sedated with pentobarbital 3-5mg/kg. Consecutive 100 gradient-echo echo planar data sets were acquired with TR/TE of 3000/50, a flip angle of 90, a FOV of 220, a 128 x 128 image matrix and a slice thickness of 5mm. Each data set contained consecutive 3 axial slices covering calcaline sulcus. An initial baseline phase of rest for 30 sec was followed by photic stimulation phase alternating with a rest phase, with a total of 10 phase per trial. Visual stimulation was performed with a flash light (8 Hg) project onto the eyelids.Results : 8 infants without PVL showed a signal decrease in the visual cortex upon visual stimulation. On the other hands, 6 out of 8 infants with PVL showed no activation in visual cortex. These 6 infants had severe strabismus and could not follow objects at 6 months after birth. And all of them had sever cerebral palsy and mental retardation at two years of age. These findings suggested that brain fMRI is a useful method to evaluate the visual function in infants.