采用优化的基于体素的形态学方法研究智力障碍儿童脑灰质容积变化

Investigation of the alteration of gray matter volume in children with mental retardation with the optimal voxel-based morphometry

目的 利用优化的基于体素的形态测量学（VBM）方法,比较病因不明且常规影像检查正常的智力障碍儿童与正常同龄儿童脑灰质容积的差异,探究患儿脑灰质发育与智力障碍间的联系.方法 选取21例智力障碍患儿和30名正常儿童进行高分辨率脑MR扫描,然后进行VBM分析,应用独立样本t检验比较两组儿童脑灰质容积总量以及不同区域灰质容积的差别.同时,对智力障碍儿童的智商评分与脑灰质容积总量进行偏相关性分析.结果 智障儿童脑灰质容积总量[（1.012±0.079）×106 mm3]明显大于正常儿童[（0.956±0.059）×106mm3],智障组与正常对照组儿童脑灰质总容积的差异具有统计学意义（t=-2.80,P＜0.05）.智障组儿童脑局部区域灰质容积较正常对照组高,脑区包括双侧丘脑、额上回、直回和颞极,以及右侧额下回、海马旁回和右侧小脑.智障组儿童脑灰质容积与智商无相关性（r=0.078,P＞0.05）.结论 VBM能够显示常规MRI表现正常的智力障碍儿童中的脑灰质发育异常.额叶-丘脑环路的脑灰质容积增加,提示其发育滞后,可能是导致儿童智力障碍的原因之一.

Objective To detect brain structural difference between children with unexplained mental retardation and children with typically normal development. Methods The high-resolution magnetic MR imaging were obtained from 21 children with unexplained mental retardation and 30 age-matched control children without intellectual disabilities. Voxel-based morphometry analysis with an optimization of spatial segmentation and normalization procedures were applied to compare differences of gray matter volume between the two groups. The total and regional gray matter volume were compared between the two groups with independent t test. Meanwhile, correlation was conducted to analyze the relationship between the total gray matter volume and intelligence quotient （IQ） with partial correlation test. Results The total gray matter volume was significantly increased in the mental retardation children [（1. 012 ±0. 079） × 106 mm3]in relative to the controls [（0. 956 ± 0. 059） × 106 mm3, t = - 2. 80, P 〈 0. 05]. Compared to controls,children with unexplained mental retardation showed significantly increased gray matter volume in different regions, including the bilateral thalami, the bilateral superior frontal gyri, the bilateral gyri rectus, the bilateral temporal poles, the right inferior frontal gyrus, right parahippocampal gyrus and the right cerebellum. No correlation was detected between the total gray matter volume and IQ in children with mental retardation （r = 0. 078 ,P 〉 0. 05）. Conclusions VBM would detect the gray matter abnormalities that were not founded in routine MR scanning. The increase of gray matter volume in the frontal-thalamus network might indicate the delayed maturation of the brain development. This might be one of the causations of mental retardation in children.