小脑延髓池肿瘤的MRI诊断——定位与征象

MRI Diagnosis of Cisterna Magna Tumors:Accurate Positioning and Characteristics

目的探讨小脑延髓池肿瘤的MRI诊断价值。方法对17例经手术病理证实的小脑延髓池肿瘤的MRI表现进行回顾性分析。所有病例均采用3.0 T MR扫描仪平扫加增强扫描,并行横断位、矢状位、冠状位重组,分析肿瘤部位、与周围组织的关系及MRI特征。结果本组中神经鞘瘤4例,肿瘤贴附于延髓背侧呈偏侧性生长,囊变明显,增强囊壁及实性部分明显强化;室管膜瘤3例,肿瘤定位于小脑延髓池,形态不规则并有囊变,可见脑脊液环绕,增强实性部分轻至中度强化;脑膜瘤3例,均为宽基底的实性肿块,增强均匀明显强化,其中1例见"脑膜尾征";血管母细胞瘤3例,2例表现为"大囊小结节";1例瘤体为实性肿块,增强后明显强化,瘤周可见粗大供血动脉;脉络丛乳头状瘤2例,为小脑延髓池内浅分叶状的肿块,周围见脑脊液环绕,信号稍不均匀,增强均见明显强化,1例见微囊变;胶质母细胞瘤1例,肿瘤来源于小脑半球并突向小脑延髓池,信号不均匀,见多发囊变及周围脑组织水肿,增强后呈"花环"状强化;脂肪瘤1例,T1WI、T2WI均呈高信号,脂肪抑制呈低信号,边界清晰,增强扫描强化不明显。结论小脑延髓池肿瘤的MRI表现各有其特点,通过MRI检查能精确定位,有助于推断肿瘤的来源,并根据信号特点进行定性诊断。

Objective To explore the MRI diagnostic value of cisterna magna tumors. Methods We retrospectively analyzed 17 cases with cisterna magna tumors. All the cases received MRI scan by using 3.0T MR machine and were confirmed by surgery and pathology. Sagittal and coronal reconstructions were acquired to made decisions by analyzing location of tumor, relation to the surrounding organs and MRI features. Results （1）There were 4 cases of Schwannoma. The lesions with obvious cystic degeneration were partially lateral to the back of medulla. Capsule and solid components of the mass were significantly enhanced. （2）There were 3 cases of ependymoma. Tumors were located in cisterna magna with irregular shapes and cystic degeneration. Cerebrospinal fluid surrounding signs can be found. Solid components of the mass were mild to moderately enhanced. （3）There were 3 cases of meningioma. All the lesions as solid mass with broad basement were close to adjacent organs. Homogenous and obvious enhancement of the masses were shown. And dural tail sign was found in 1 case. （4）There were 3 cases of hemangioblastomas. The typical ＂large cyst with small nodule＂ signs were shown in 2 cases. Another case showed a significantly enhanced solid mass with blood supply arteries. （5）There were 2 cases of choroid plexus papillomas. The shallow lobulated masses with homogenous signal located in cisterna magna. Cerebrospinal fluid surrounding signs can be found. Obvious enhancement were found in both cases, and microcystic degeneration in 1 case. （6） There was only 1 case of glioblastoma. The mass with inhomogeneous signal and obvious enhancement derived from cerebellar hemisphere growing to eisterna magna. Multiple cystic degeneration and edema of surrounding brain tissue were shown. （7）There was 1 case of lipoma. The mass with high signal on both T1WI and T2WI was located in cisterna magna. The mass showed low signal on fat suppression sequence, and without enhancement. Conclusion According to MRI characteristics and exact location, we can make accurate qualitative diagnosis for the tumors of cisterna magna.