颞侧偏盲患者单眼水平半视野刺激的fMRI研究

Horizontal visual hemi-field stimulation on single eye in patients with hemianopia:a functional MRI study

目的:观察正常人单眼水平半视野刺激下视觉皮层的激活形式;探讨fMRI用于评价颞侧偏盲患者初级视觉皮层激活形式的可能性。资料与方法:对13例颞侧偏盲的垂体大腺瘤患者和15名正常志愿者进行组块设计的fMRI实验,所有受试者分别接受左眼颞侧、左眼鼻侧、右眼颞侧和右眼鼻侧视野刺激,刺激内容为水平单侧40°黑白翻转棋盘格,对照内容为黑色屏幕中心的白色"+"。采用1.5TMR扫描仪采集数据,采用SPM2软件进行后处理,获得对照组各种刺激下的平均激活图,分析患者组视野缺损与初级视觉皮层激活形式之间的对应关系。结果:在排除了扫描过程中头动及噪声影响后,患者组和对照组最终各入组10例。对照组单眼颞侧视野刺激时表现为对侧视觉皮层激活,鼻侧视野刺激时表现为同侧初级视觉皮层激活为主。患者组在接受颞侧视野刺激时双侧视觉皮层均未见激活,而给予鼻侧视野刺激时均表现为同侧视觉皮层激活。结论:正常情况下视野与初级视觉皮层之间存在对应关系,颞侧偏盲患者表现为以对侧初级视觉皮层激活下降为主,fMRI是反映视交叉异常对视觉皮层影响的有效方法。

Objective： To observe response of primary visual cortex to horizontal visual hemi-field stimulation on single eye in subjects with hemianopia and to discuss the probability of evaluating the activation of visual cortex with functional MRI （fMRI）. Materials and Methods： Thirteen patients with pituitary adenoma and fifteen normal volunteers as control were recruited in this study. Block-designed fMRI was performed with 1.5T MR scanner. Black and white check board（horizontal u- nilateral 40 degree visual field） and ＂＋＂ were used as stimulus and control respectively. Bilateral eyes received nasal and temporal side stimulus individually. The fMRI data were processed with SPM 2. Average mappings of subjects were obtained. The relationship between visual field deficits and activation in visual cortex was analyzed for patients group. Results： Ten pa- tients and 10 normal subjects were selected for group analysis after head motion effect was ruled out. In normal subjects, the eontralateral occipital lobe showed activation to temporal visual field stimulation and ipsilateral occipital lobe showed activation to nasal visual field stimulation. In patients group, bilateral visual cortex showed no activation to temporal visual field stimula- tion and ipsilateral occipital lobe showed activation to nasal visual field stimulation. Conclusion： There was a corresponding relationship between visual field and activation of visual cortex in normal subjects. Patients with hemianopia mainly presented with function decrease in contralateral visual cortex, fMRI is an effective method for studying affection of optic chiasm abnor- mality on visual cortex.