眶骨内溶骨性脑膜瘤的CT和MRI表现

CT and MRI appearance of osteolytic intraosseous meningioma of the orbit

目的探讨眶骨内溶骨性脑膜瘤的CT和MRI表现。方法回顾性分析2001年6月至2008年2月期间经组织学证实的眶骨内溶骨性脑膜瘤8例患者的影像资料。结果8例均为良性病变，其中上皮型5例，纤维型2例，过渡型1例。病变位于眼眶外上壁4例，外壁3例，眶尖区蝶骨小翼1例。6例呈卵圆形，2例呈不规则形，边界较清楚，病灶最大径18～47mm，平均29mm。CT表现：6例骨质破坏，边缘毛糙，2例骨质呈囊状、膨胀性改变，边缘清楚；与脑灰质比较，平扫病变呈等密度7例，稍低密度1例；3例增强后呈中度强化。MRI表现：与脑灰质比较，T1WI呈稍低信号2例，等信号6例；T1WI呈稍高信号2例，等信号6例；增强后呈中度强化6例，明显强化2例；其中3例病变内部信号不均匀，增强后呈不均匀强化。3例行MRI动态增强扫描，2例时间-信号强度曲线为速升缓降型，1例为速升速降型。MRI清晰显示病变伴发或继发性改变。结论MRI所示等信号、中度强化是该病的较特征性表现；CT有利于判断病变的起源，MRI能够更清楚、准确显示病变的范围，联合使用2种影像检杏方法能够对该病的诊断、治疗提供更全面的信息。

Objective To study CT and MRI findings of osteolytic intraosseous meningioma of the orbit and evaluate their clinical significance. Methods Eight cases of osteolytic meningioma arising from the orbital bone were confirmed by histopathology. CT and MRI findings of these meningiomas were analyzed retrospectively. Results Among the 8 cases of benign intraosseous meningioma of the orbit, 5 were meningotheliomatous, 2 fibrotic and 1 transitional in histopathology. Their locations included 4 in the lateral and superior walls, 3 in the lateral wall, and only one in the lesser wing of sphenoid bone neighboring the orbital apex. The maximum diameter of the lesions ranged from 18 to 47 nun （mean,29 mm）. All lesions showed a relatively well-defined margin with 6 cases having an oval shape, and 2 cases having an irregular contour. On CT, 6 lesions demonstrated bony destruction with coarse margin and 2 lesions showed bony cystic dilatation with a well-defined margin. On non-contrast CT, 7 lesions showed isodensity to gray matter and 1 lesion revealed a slight hypodensity. Three lesions showed moderate enhancement on posteontrast CT. On MR T1WI, 6 lesions of osteolytie intaosseous meningioma of the orbit demonstrated isointensity compared to gray mater and 2 lesions slight hypointyensity. On T2 WI, 6 lesions showed isointensity and 2 lesions slight hyperintensity. On contrast-enhanced MRI, 6 lesions showed moderate enhancement and 2 lesions exhibited marked enhancement. Heterogeneous signal intensity with inhomogeneous enhancement was seen in 3 lesions on MR images. The time-intensity curve （TIC） of dynamic contrast enhancement of 3 tumors on MRI appeared as rapid enhancing and slow wash-out pattern in 2 cases, rapid enhancing and rapid wash-out pattern in the third one. In comparison to CT, MRI appeared to show the secondary and complicated changes of the lesions more clearly. Conclusions Isointensity with moderate contrast enhancement appears to be the typical manifestation of intransseous osteolytic meningioma of the orbit on MR. CT is useful for judging the original site of these lesions. MRI is superior to CT in depicting the extent of these lesions. Combined imaging findings of CT and MRI can provide more comprehensive information for diagnosis and therapy of these tumors.