间歇性外斜视患者大脑皮层灰质结构基于体素的磁共振形态学研究

A voxel-based magnetic resonance study of cortical gray matter structures in intermittent exotropia

目的:基于体素探讨间歇性外斜视患者(IXT)大脑皮层灰质体积的变化,并分析该变化与临床体征的相关性。方法:横断面研究。连续收集2021年3月至2022年5月于天津市眼科医院就诊的IXT患者15例作为斜视组,其中男性7例,女性8例,年龄(23.5±5.2)岁。并选取10名健康人作为对照组,其中男性3人,女性7人,年龄(27.0±7.5)岁。所有受试者进行斜视度和Titmus立体视功能检查。行磁共振扫描获得大脑三维高分辨率图像数据,进一步采用基于体素的形态学研究方法对数据进行预处理,并采用MATLAB软件中SPM工具包分析两组图像差异,选取了脑灰质体积分析中显示出结构异常的脑区作为感兴趣区域(ROI),通过MarsBaR软件计算ROI灰质体素与该受试者全脑灰质体素平均值的比值,分析该比值与斜视度数和Titmus立体视功能检查结果常用对数(lgTS)的相关性。结果:两组受试者年龄、性别分布、双眼屈光度数的差异均无统计学意义(均P>0.05),斜视度数和立体视功能的差异均有统计学意义(均P<0.001)。相较于对照组,斜视组患者灰质体素减少的脑区有大脑半球内侧面楔叶(减少89体素值)、左侧舌回(减少176体素),左侧枕中回V3区(减少30体素)、右侧额叶中央前回(减少192体素)、左侧海马旁回灰质(减少20体素),双侧丘脑后外侧核(左侧和右侧分别减少100和40体素)体积减小,差异均有统计学意义(均P<0.001);灰质体素增加的脑区有双侧基底神经节壳核(左侧和右侧分别增加60和76体素)、左侧前扣带区(增加36体素),差异均有统计学意义(均P<0.001)。根据组水平分析得到两组受试者存在结构差异的10个脑区作为ROI。灰质体积比值与外斜视度数呈负相关(均P<0.05)的ROI为左侧楔叶(r=-0.670)、左侧枕中回V3区(r=-0.610)和左侧舌回(r=-0.684);灰质体积比值与lgTS呈负相关(均P<0.05)的ROI有左侧楔叶(r=-0.568)和右侧中央前回(r=-0.563)。结论:IXT患者的初级视皮层V1和V2区之间的水平连接区域灰质体积减小;斜视程度严重者舌回和背侧视觉通路V3区的灰质体积降低明显,立体视功能受损越严重者额叶中央前回(BA6区)的灰质体积越小。

Objective To explore the changes in gray matter volume of the cerebral cortex in patients with intermittent exotropia(IXT)using the voxel-based analysis and to analyze the correlation between these changes and clinical manifestations.Methods This was a cross-sectional study.A collection of 15 consecutive patients diagnosed with IXT at Tianjin Eye Hospital from March 2021 to May 2022 formed the exotropia group,which comprised 8 males and 7 females,with an average age of(23.5±5.2)years.Ten healthy individuals,3 males and 7 females,with an average age of(27.0±7.5)years,were selected as the control group.All participants underwent assessments of exotropia severity and Titmus stereoacuity.Three-dimensional high-resolution brain images were obtained through MRI scans.Voxel-based morphometry was employed to preprocess the MRI data,and the SPM toolbox in MATLAB was utilized to analyze differences of images between the two groups.Regions of interest(ROI)with structural abnormalities in the gray matter volume analysis were selected,and the ratio of gray matter voxel values in the ROI to the mean gray matter voxel values of the whole brain for each participant was calculated using the MarsBaR software.The correlation between this ratio and exotropia severity as well as the common logarithm of Titmus stereoacuity was analyzed.Results The differences in age,gender distribution,and refractive error between the two groups were not statistically significant(all P>0.05).However,there were statistically significant differences in the degree of strabismus and Titmus stereoacuity(both P<0.001).Compared to the control group,patients in the strabismus group exhibited decreased gray matter volume in several brain regions,including the wedges of the medial surface of the cerebral hemisphere(decreased by 89 voxels),the left lingual gyrus(decreased by 176 voxels),the left calcarine sulcus V3 area(decreased by 30 voxels),the central anterior gyrus of the right frontal lobe(decreased by 192 voxels),the gray matter of the left hippocampal gyrus(decreased by 20 voxels),and the bilateral lateral geniculate nuclei(decreased by 100 and 40 voxels on the left and right sides,respectively).These differences were all statistically significant(all P<0.001).Additionally,there was an increase in gray matter volume in several brain regions,including the bilateral caudate nuclei(increased by 60 and 76 voxels on the left and right sides,respectively)and the left precentral gyrus(increased by 36 voxels).These differences were also statistically significant(all P<0.001).A group-level analysis identified 10 brain regions with structural differences between the two groups,which were used as ROI.The gray matter volume ratio was negatively correlated with the degree of exotropia(all P<0.05)in the ROI of the left wedges(r=-0.670),left calcarine sulcus V3 area(r=-0.610),and left lingual gyrus(r=-0.684).The gray matter volume ratio was negatively correlated with lgTS(all P<0.05)in the ROI of the left wedges(r=-0.568)and the central anterior gyrus of the right frontal lobe(r=-0.563).Conclusions Patients with IXT exhibit decreased gray matter volume in the horizontal connection areas between the primary visual cortices V1 and V2.The reduction in gray matter volume of the lingual gyrus and the dorsal visual pathway V3 area becomes more pronounced with increasing exotropia severity,while the gray matter volume of the precentral gyrus(BA6 area)decreases with worsening stereoacuity.