MRI 在脊索样脑膜瘤诊断及与其他脑膜瘤鉴别诊断中的价值

目的：探讨脊索样脑膜瘤(CM)的 MRI 特征性表现,并与其他脑膜瘤相鉴别。方法回顾性分析经手术病理确诊的7例 CM 患者的临床及 MRI 资料,定性分析其 MRI 各序列的信号特征,并进一步定量分析肿瘤各序列的标准化信号强度比,包括标准化 T1 WI 信号强度比(NT1)、标准化 T2 WI 信号强度比(NT2),标准化表观扩散系数比(NADC)、标准化 T1增强信号强度比(NCE)。采用 Fisher 精确检验和 Dunnett T 3检验法与经病理证实的非脊索样脑膜瘤(34例Ⅰ级脑膜瘤、16例非脊索样Ⅱ级脑膜瘤、5例Ⅲ级脑膜瘤)进行比较。结果CM 在 T2 WI 序列上均表现为高信号,非脊索样脑膜瘤则表现为等、低或稍高信号；CM 在扩散加权成像(DWI)上信号多变,但均无明显扩散受限,表观扩散系数(ADC)图上表现为高信号,增强扫描后实性部分明显强化。CM 的定量指标 NT2、NADC 及 NCE 均高于其他脑膜瘤(P 均<0.01),而 NT1无明显统计学差异(P =0.889)。病灶内有无囊变坏死、T2 WI 是否可见“流空效应”、瘤周水肿程度、是否出现脑膜尾征及宽基底对鉴别 CM 和其他脑膜瘤意义不大。结论CM 的MRI 表现有一定特征性,T2 WI 多表现为高信号,扩散不受限,强化程度更明显,NT2、NADC 及 NCE 的测定有助于提高其术前诊断的准确性。

The value of MRI in diagnosis of chordoid meningioma and differenciation with other meningiomas

Objective To analyze the MRI features of chordoid meningioma (CM),and to compare with other meningiomas. Methods Clinical and MRI features of 7 patients with CM confirmed by pathology were analyzed retrospectively.Featrues of every MRI sequence were investigated qualitatively.Meanwhile normalized signal ratios of each sequence were analyzed furtherly,including normalized T1 weighted image intensity ratios (NT1 ),normalized T2 weighted image intensity ratios(NT2 ),normalized ADC ratios (NADC)and normalized T1 WI contast enhancement intensity ratios (NCE).Fisher ’s exact test and Dunnett T 3 test were employed to analyze the difference of CM and nonchordoid meningiomas (34 cases of WHO grade Ⅰ meningioma,1 6 cases of nonchordoid WHO grade Ⅱ meningioma,and 5 case of WHO grade Ⅲ meningioma).Results The CM showed hyperintensity on T2 WI and meanwhile other nonchordoid meningiomas demonstrated isointensity,hypointensity or slight hyperintensity on T2 WI.Evaluations of DWI revealed variable signal intensities of CM.But all 7 cases had no obvious restricted diffusion,and increased signal was seen on the ADC map in each patient.The solid parts of CM enhanced markedly after contrast agent injection.Quantitative indicators NT2 , NADC and NCE of CM were higher than other meningiomas(P <0.01),but NT1 showed no statistic difference between CM and other meningiomas (P =0.889).Whether there was cyst,necrosis,or"flow void sign" on T2 WI,and no matter with or without perifocal edema,dural tail sign and a broader base among meningiomas had no significance in differentiating CM and other meningiomas.Conclusion CM has typical MRI features.The tumors show hyperintensity on T2 WI,especially have no obvious restricted diffusion and enhance markedly after contrast.The measurement of NT2 ,NADC and NCE enables reliable preoperative prediction of the atypical histopathologic diagnosis.