Maricich S M, Azizi P, Jones J Y, Morriss M C, Hunter J V, Smith E O, Miller G
Department of Pediatrics, Section of Neurology, Baylor College of Medicine, Houston, TX, USA.
AJNR Am J Neuroradiol. 2007 Sep;28(8):1602-5. doi: 10.3174/ajnr.A0602.
A common isolated reported finding in brain imaging studies on developmentally delayed children is delayed myelination. We hypothesized that brain MR imaging scans of these children would show delayed subcortical myelination of white matter with specific involvement of the subcortical U-fibers as these represent terminal zones of myelination and are the last areas to myelinate.
A total of 93 children (31 controls, 62 with idiopathic developmental delay [IDD]) aged 17 to 46 months were identified on the basis of having brain MR imaging for evaluation of IDD (cases) or for another condition (controls). Children with diseases that primarily affect white matter or overt intracranial lesions or malformations were excluded. IDD was defined as psychomotor retardation without a clear cause on the basis of history, physical, genetic, metabolic, and neuroimaging examinations. Developmental quotients (DQs) were calculated for all children with IDD on the basis of clinical history, examination, and psychometric testing. Three board-certified pediatric neuroradiologists examined axial T2-weighted brain images and used a published scoring system to rate the extent of myelination in the frontal, temporal, parietal, and peritrigonal brain regions. In addition, subcortical U-fibers in the frontal, temporal, and parietal lobes were scored separately. Data were analyzed at both the intraobserver and interobserver levels, and scores were compared between groups and tested for interactions with age and DQ.
There were no differences in the timing or extent of myelination in the control and IDD groups at any age in any brain region. In the IDD group, there was no relationship between myelination scores and DQ or developmental domain.
Our findings did not support the hypothesis that there is a correlation between IDD and the maturity of myelination, including the terminal zones, as seen on conventional brain MR imaging. Neuroimaging evaluation of maturity of subcortical myelination is not a marker of IDD in young children, and the isolated "finding" of delayed myelination should be interpreted with caution.
在发育迟缓儿童的脑成像研究中，一个常见的单独报告发现是髓鞘形成延迟。我们假设这些儿童的脑部磁共振成像扫描将显示白质的皮质下髓鞘形成延迟，特别是皮质下U形纤维受累，因为这些代表髓鞘形成的终末区域，是最后髓鞘化的区域。
基于因评估特发性发育迟缓（IDD）（病例组）或其他病症（对照组）而进行脑部磁共振成像，共确定了93名年龄在17至46个月的儿童（31名对照组，62名患有特发性发育迟缓）。排除主要影响白质的疾病或明显的颅内病变或畸形的儿童。根据病史、体格检查、遗传学、代谢和神经影像学检查，将IDD定义为无明确病因的精神运动发育迟缓。根据临床病史、检查和心理测量测试，为所有患有IDD的儿童计算发育商（DQ）。三位获得委员会认证的儿科神经放射学家检查了轴向T2加权脑图像，并使用已发表的评分系统对额叶、颞叶、顶叶和三角区周围脑区的髓鞘形成程度进行评分。此外，分别对额叶、颞叶和顶叶的皮质下U形纤维进行评分。在观察者内部和观察者之间两个层面分析数据，并比较组间评分，测试其与年龄和DQ的相互作用。
在任何年龄的任何脑区，对照组和IDD组在髓鞘形成的时间或程度上均无差异。在IDD组中，髓鞘形成评分与DQ或发育领域之间没有关系。
我们的研究结果不支持如下假设，即如传统脑部磁共振成像所见，IDD与包括终末区域在内的髓鞘形成成熟度之间存在相关性。皮质下髓鞘形成成熟度的神经影像学评估不是幼儿IDD的标志物，髓鞘形成延迟这一单独的“发现”应谨慎解读。
