Pillai Shibu, Singhal Ash, Byrne Angela T, Dunham Chris, Cochrane D Douglas, Steinbok Paul
Division of Pediatric Neurosurgery, Department of Surgery, University of British Columbia and British Columbia's Children's Hospital, Vancouver, Canada.
Childs Nerv Syst. 2011 Sep;27(9):1407-11. doi: 10.1007/s00381-011-1499-5. Epub 2011 Jul 6.
Some investigators have suggested that medulloblastomas can be distinguished from other cerebellar neoplasms by demonstrating "restricted diffusion" on the Apparent Diffusion Coefficient (ADC) map obtained from diffusion-weighted imaging (DWI) sequences on magnetic resonance imaging. Previous authors have postulated that this observed restricted diffusion is a reflection of very high cell density. There has been a tendency to assert that pediatric medulloblastoma uniformly demonstrates restricted diffusion on DWI. However, our clinical observation has been that there are pediatric medulloblastomas that exhibit normal or even increased diffusion on DWI. The current study was undertaken primarily to determine whether restricted diffusion is uniformly present in pediatric medulloblastoma and secondly to look for pathological features that might distinguish medulloblastomas with and without restricted diffusion.
The DWI characteristics of pathologically confirmed medulloblastomas diagnosed at our institution were retrospectively reviewed. The ADC was obtained in two non-overlapping, solid, non-hemorrhagic, non-necrotic regions of tumor and averaged. An ADC below 1 × 10(-3) mm(2)/s was considered to represent restricted diffusion. A detailed pathologic review of each tumor was conducted.
Ten cases of medulloblastoma were reviewed, of which two demonstrated average ADCs above 1 × 10(-3) mm(2)/s (1.223 and 1.169 × 10(-3) mm(2)/s, respectively), indicating no restricted diffusion. Pathologic review revealed that both of these non-restricting cases displayed a lack of reticulin deposition by light microscopy.
DWI does not appear to be an entirely reliable means of distinguishing medulloblastomas from other cerebellar neoplasms. Histologically, restricted diffusion in medulloblastomas may be related to reticulin deposition.
一些研究人员提出，通过在磁共振成像的扩散加权成像（DWI）序列获得的表观扩散系数（ADC）图上显示“扩散受限”，可以将髓母细胞瘤与其他小脑肿瘤区分开来。先前的作者推测，观察到的扩散受限反映了非常高的细胞密度。人们倾向于断言，小儿髓母细胞瘤在DWI上均表现出扩散受限。然而，我们的临床观察发现，有些小儿髓母细胞瘤在DWI上表现为正常甚至扩散增加。本研究主要旨在确定小儿髓母细胞瘤中是否均存在扩散受限，其次是寻找可能区分有或没有扩散受限的髓母细胞瘤的病理特征。
回顾性分析我院经病理确诊的髓母细胞瘤的DWI特征。在肿瘤的两个不重叠、实性、非出血、非坏死区域获取ADC值并求平均值。ADC值低于1×10⁻³mm²/s被认为代表扩散受限。对每个肿瘤进行详细的病理检查。
回顾了10例髓母细胞瘤病例，其中2例的平均ADC值高于1×10⁻³mm²/s（分别为1.223和1.169×10⁻³mm²/s），表明无扩散受限。病理检查显示，这两个无扩散受限的病例在光学显微镜下均缺乏网状纤维沉积。
DWI似乎不是区分髓母细胞瘤与其他小脑肿瘤的完全可靠方法。从组织学上看，髓母细胞瘤中的扩散受限可能与网状纤维沉积有关。
