中枢神经系统脱髓鞘性假瘤的MRI表现

MRI of demyelinating pseudotumor of the central nervous system

目的 描述中枢神经系统脱髓鞘性假瘤的MRI表现 ,探讨该病变的病理学改变特征以及MRI诊断价值和限度。方法 对 7例经手术病理证实及 1例经临床证实的中枢神经系统脱髓鞘性假瘤进行了MR检查 ,对其MR影像学表现特征进行了回顾性分析。结果 MRI显示 8例病变均表现为局限性肿块 ,邻近未见伴有多发病灶 ;5例呈均匀长T1信号 ,2例呈不均匀长T1信号 ,1例呈短T1及长T1混杂信号 ;5例呈均匀长T2 信号 ,3例呈不均匀长T2 信号 ;7例经钆喷替酸葡甲胺 (Gd DTPA)增强者病灶均有明显强化 ,其中 1例左额顶叶病灶强化后有垂直于侧脑室分布的倾向 ,1例颈段脊髓病灶可见以背侧白质为主的强化 ;MR复查未见病变复发征象 ,其中 1例激素治疗后病变逐渐缩小。结论 中枢神经系统脱髓鞘性假瘤的临床和影像学诊断较困难 ,MR检查常将本病误诊为肿瘤。诊断时若能认真分析临床病史并仔细观察MRI表现 (特别是增强MRI表现 ) ,则有可能提出本病的诊断 ,此时可以先使用激素试验治疗 ,以避免手术或放射治疗造成的严重损伤。

Objective To describe the MR manifestations of demyelinating pseudotumor of the central nervous system (CNS), and to discuss the pathologic features and MR diagnostic value and limit in this disease entity. Methods Seven pathologically proved and one clinically proved cases of demyelinating pseudotumor of CNS were studied with MR imaging, and the MR imaging features were retrospectively analyzed. Results MR imaging demonstrated localized mass without adjacent multiple accompanying lesions in all 8 cases. On T 1WI, the lesions showed homogenous low signal in 5 cases, inhomogenous low signal in 2 cases, and mixed high and low signal in 1 case. On T 2WI, the lesions presented as homogenous high signal in 5 cases and inhomogenous high signal in 3 cases. Of the 7 cases with Gd DTPA administration, marked enhancement was seen in each case. The enhancement pattern of vertical distribution to the lateral ventricle was demonstrated in left frontoparietal lobe in one case, and predominant dorsal white matter enhancement of the cervical spinal cord was revealed in another case. Follow up MR imaging showed no lesion recurrence, and gradual shrinkage of the lesion after steroid therapy was demonstrated in one case. Conclusion It is a difficult task to make the correct diagnosis of CNS demyelinating pseudotumor based on the clinical information and imaging findings, and this disease entity is often misdiagnosed as tumor by MR imaging. Thorough analysis of the clinical history and careful observation of MR manifestations (especially contrast enhanced MR findings) would be helpful in diagnosing the demyelinating pseudotumor and, in such circumstances, providing test steroid therapy, thus avoiding the devastating injury caused by surgery or radiation therapy.