成人髓母细胞瘤的MRI征象分析

MRI Features of Medulloblastoma in Adults

目的 探讨成人髓母细胞瘤的MRI征象,以提高对该病的认识及术前诊断准确率。方法 回顾性分析12例（男7例,女5例,年龄18-57岁,平均34.1岁）经手术病理证实的成人髓母细胞瘤患者MRI资料。所有患者均行MRI平扫及增强扫描,7例加做扩散加权成像（DWI）,观察病灶的位置、大小、形态、边界、信号特点、强化特征。结果 12例中,单发病灶11例,1例为多发,共13个病灶;小脑半球5个,小脑半球-蚓部3个,小脑蚓部4个,第四脑室1个;7个广基底贴于脑表面或小脑幕,1例跨左小脑幕累及幕上,1例经桥臂累及脑干。1个病灶T1WI及T2WI均呈等信号,12个病灶T1WI呈低或稍低信号,T2WI呈等或稍高信号;DWI呈稍高或高信号。12个病灶出现不同程度囊变,裂隙状或斑片状至大囊变;增强扫描11个病灶不均匀强化,9个呈轻中度强化,4个明显强化;脑膜尾征3例,1例见蛛网膜下腔种植转移,12个病灶瘤周无或轻度水肿。结论 成人髓母细胞瘤以小脑半球、小脑半球-蚓部多见,且紧贴脑表面或小脑幕,可多发,易囊变,DWI呈高信号,增强扫描呈不均匀轻中度强化,无或轻度瘤周水肿,较少出现蛛网膜下腔种植转移,MRI表现具有一定的特征性,有助于诊断。

Objective To analyze the MRI features of medulloblastoma in Adults and to improve its knowledge and diagnostic accuracy preoperatively. Methods Twelve adult patients with medulloblastoma confirmed by operation and pathology were retrospectively analyzed. All patients underwent conventional MRI and contrast enhancement scans at the same time; diffusion-weighted （DWI） MRI was also performed in 7 patients. Image characteristics such as location, size, shape, margin, signal, and pattern of enhancement were analyzed. Results There were 13 lesions in 12 patients with one case having 2 lesions. 5 lesions were located in the cerebellar hemisphere, 3 in the hemisphere-vermis, 4 in the vermis and 1 in the fourth ventricle. 7 lesions extended to the brain surface or the tentorium, 1 lesion crossed the left tentorium involving the temporal lobe and 1 invaded the brain stem through the right cerebellar peduncle. One lesion showed isointensity on Tl WI and T2 WI, others showed slight hypo-intensity or hypo-intensity signal on T1WI, slight hyper-intensity signal on T2WI, slight hyperinteusity or hyperintensity signal on DWI. 12 （92.3 % ） lesions showed cystic degeneration varying from cleft-like to large cystic. 11 lesions had heterogeneous enhancement, 9 lesions had mild to moderate enhancement, and 4 lesions had marked enhancement. Only one case showed subarachnoid seeding metastases in all 12 cases. There were no or slight edema around the tumors in 12 lesions. Conclusion Most medulloblastomas in adults occurred in cerebellar hemisphere or hemisphere-vermis, which may be multiple. The tumors are vulnerable to cystic degeneration and tend to extend to the brain surface or the tentorium. Medulloblastomas displayed mild to moderate enhancement with no or slight edema around the tumors. They have less subarachnoid seeding metastases. Therefore, the MRI manifestations have certain characteristics contributing to the diagnosis of medulloblastoma in adults.