成人髓母细胞瘤12例误诊的MRI表现及分析

MRI Features of Medulloblastoma in Adults and Analysis of Misdiagnosis

目的探讨成人髓母细胞瘤(MB)MRI表现并分析误诊原因。方法回顾性分析12例经病理证实的成人MB的MRI影像特点,并结合病理对照,同时分析讨论误诊原因。结果均为单发病灶,其中右侧小脑半球3例、左侧小脑半球5例(波及小脑蚓部2例)、小脑蚓部2例、第四脑室1例、左侧桥小脑角区1例。病灶呈椭圆形及类圆形7例,分叶状5例;边界清晰10例,边界不清2例。实性部分T1WI多呈稍长或等T1信号,T2WI多呈等或稍长T2信号,9例信号不均匀伴囊变信号,扩散加权成像(DWI)均呈高信号,表观扩散系数(ADC)图呈稍低信号。7例呈广基底贴于局部脑表面或小脑幕。增强后均明显强化,其中9例呈不均匀强化、3例全瘤明显均匀强化,4例见"脑膜尾征"。9例重度占位效应、3例轻度占位效应,瘤周水肿重度4例、轻度4例、无4例。术前多误诊为胶质瘤、脑膜瘤、室管膜瘤。结论成人MB多位于小脑半球或小脑半球累及蚓部,且多紧贴脑表面或小脑幕,多呈稍长T1、等T2信号,多囊变,DWI呈高信号,强化方式及强化程度多种多样,多呈较明显不均匀强化,可伴"脑膜尾征",多无或轻度瘤周水肿,其MRI表现具有一定的特征性。误诊多由于年龄因素及定位脑外病变。

Objective To investigate the MRI findings of adult medulloblastoma and analyze the causes of misdiagnosis.Methods MRI features of 12 cases of adult medulloblastoma which were confirmed by pathology were analyzed retrospectively.Combining the imaging features with the pathological control analysis,the reasons for misdiagnosis were then discussed.Results All of the lesions were solitary,including 3 cases of right cerebellar hemisphere,5 cases of left cerebellar hemisphere(with 2 cases also involving the cerebellar vermis),2 cases of cerebellar vermis,1 case within the fourth ventricle,and 1 case of left cerebellopontine angle area.7 lesions were oval or round,5 lesions were lobulated,with clear borders in 10 cases and ill-defined borders in 2 cases.The solid part showed mostly slightly longer or equal signal on T1WI,and showed mostly equal or slightly longer T2 signal on T2WI.9 cases showed uneven signal with cystic degeneration,DWI showed high signal,ADC showed slightly lower signal.Seven of them were attached to the local brain parenchymal surface or tentorium cerebelli with a wide base.After enhancement,all lesions enhanced significantly,including 9 cases with uneven enhancement,3 cases with homogeneous enhancement,and 4 cases with dural tail sign.There were 9 cases of severe mass effect,3 cases of mild mass effect,4 cases of severe edema,4 cases of mild edema and 4 cases of no edema.Preoperative misdiagnosis included glioma,meningioma and ependymoma.Conclusion Adult medulloblastoma mostly located in cerebellar hemisphere or cerebellar hemisphere involving vermis,and often closed to the surface or tentorium cerebelli.Most lesions showed slightly longer T1 and isointense T2 signal,Often with cystic changes,DWI showed high signal,enhancement mode and intensity were varied.Most lesions exhibited obvious uneven enhancement.Dural tail sign can be seen,mostly in the absence or presence of mild peritumoral edema.The MRI findings of medulloblastoma in adults have certain characteristics.Misdiagnosis is mostly due to age and location of extracerebellar lesions.