Meningiomas are common, intracerebroventricular meningiomas are rare, and intracerebroventricular cases have not been reported evenly in the literature of more than 60 cases of meningiomas in China [1] [2]. From November 1997 to October 2004, 136 cases of meningioma were admitted to our hospital, and 2 cases grew in the intracerebral ventricles, and the MRI performance was analyzed as follows. Lu Zhanxing, Department of Radiology, General Hospital of Pingmei Shenma Medical Group
1. Materials and methods
1.1 General data: A total of 136 cases of meningiomas were confirmed by surgical pathology. There were 2 cases growing in the lateral brain, 1 male, 46 years old, and 1 female, 44 years old. The pathology was fibroblast type meningioma.
1.2 MRI examination method: 0.23T open magnetic resonance imaging system with head orthogonal phased array coil was used. Plain scan: transverse axial, sagittal, coronal, T2WI: fast spin echo (FSE) TR/TE: 5800ms/30ms. t1WI: three-dimensional field echo volume scan (FE3D) (FE also called gradient echo sequence) TR/TE: 35ms/12ms. layer thickness 5-8mm, no interval volume scan. fov: 25cm. matrix: 192× 256, 256×256. Enhanced scan: the reference localization image and scan parameters corresponding to the flat scan were used. The contrast agent was Magnevist 0.2 mmol・kg-1, and the dough was injected within 1~3 minutes in the median elbow vein, and the first sequence was scanned within 5 minutes.
2 Results
2.1 Coincident MRI performance: site: within the lateral ventricular triangle. Signal: the signal is basically homogeneous. In T1WI signal is homogeneous, signal intensity is higher than cerebrospinal fluid, equal to cerebral gray matter and lower than cerebral white matter; T2WI signal is less homogeneous, with speckled low signal, lower than cerebrospinal fluid, equal to cerebral gray matter and higher than cerebral white matter. Margin: the lesion margin was clear. Intensity: significant homogeneous abnormal contrast enhancement. Cerebral edema: not seen.
2.2 Individual MRI performance: size: about 4.7 cm × 4.8 cm × 4.7 cm in female cases and about 1.8 cm × 2.0 cm × 1.7 cm in male cases. signal: smaller lesion with relatively homogeneous signal in male cases. Morphology: female cases were spherical and male cases were spherical with lobulation. Tumor vascularity: In female cases, clear blood supply arteries were seen emanating from the choroid plexus. In male case, the blood vessels are not clear, but there are vessels immediately adjacent to the choroid plexus. Complications: The female case combined with obvious obstruction of the posterior and inferior horn of the affected lateral ventricle; the male case did not show this.
3 Discussion
3.1 MRI signal: fibroblastic meningioma is one of the more common pathological types of meningioma. Its signal is quite characteristic due to the predominantly fibroblast composition, dense cell arrangement, and abundant interstitium with few water molecules inside the tumor [3][4]. That is, the tumor foci are dominated by basically homogeneous medium T1 medium T2 signal, on top of which there are low or/and high signals of different morphology, size and amount, and the smaller the tumor is, the more obvious the T1 and other T2 signal features are. In T1WI, the signal is uniform and the signal intensity is higher than cerebrospinal fluid, equal to cerebral gray matter and lower than cerebral white matter; in T2WI, the signal is less uniform and has speckled low signal, lower than cerebrospinal fluid, equal to cerebral gray matter and higher than cerebral white matter. Therefore, the tumor growth in the intracerebroventricular space forms a good natural contrast with the cerebrospinal fluid, which makes it easy to identify the lesion boundary. Enhanced scans after intravenous gadolinium dosing with tumors with markedly abnormal contrast enhancement are another signal characteristic of meningiomas. In the ventricles, the enhancement is more clearly shown due to cerebrospinal fluid contrast. Calcification and cystic changes within the lesion are responsible for the inhomogeneous enhancement.
3.2 Tumor vasculature: Meningioma arterioles originate from the dura mater and drain into superficial cerebral veins or venous sinuses, which can be clearly visualized by MRI [4]. Similarly, the tumor vessels of meningioma in the ventricles of the brain can be clearly shown on plain scan and enhancement due to the water backing, but it is not easy to distinguish the nature of the vessels as arteries or veins unless the vascular pathway is characteristic.
3.3 Hydrocephalus: Extraventricular meningiomas rarely cause hydrocephalus unless they compress the ventricles. However, when intraventricular tumors occupy the cerebrospinal fluid circulation channels, they can reverse the direction of cerebrospinal fluid flow to form obstructive hydrocephalus. Unlike choroid plexus papilloma, the latter causes hydrocephalus resulting in generalized enlargement of the periventricular ventricles.
3.4 Other MRI features, “meningeal tail sign” is a common sign of meningioma, which is caused by dural arachnoid enhancement and is not seen in intraventricular meningioma. Calcifications are also uncommon. There is a small amount of cystic degeneration, but no hemorrhage.
4 CONCLUSION: Intracerebroventricular fibroblastic meningiomas, although rare, can still be recognized because they have MRI features similar to those of meningiomas of the same pathology in other parts of the brain. This disease should be differentiated mainly from intracerebroventricular choroid plexus papillomas which are more common in pediatrics and adolescents and meningiomas which are more common in middle age.
5References.
1, Yuan Shuwei, Luo Tianyou, Wu Jingquan et al, Relationship between MRI manifestations and pathological staging of intracranial meningioma, Journal of Chongqing Medical University, 2003 (28) 5: 639￣655.
2.Wang Zhongqiu Shi Zengru Guo Xianri, Diagnosis of intracranial meningioma by magnetic resonance (with analysis of 65 cases) Journal of Clinical Radiology, 1994 (13) 6: 330~333.
3. Chen Xingrong, Shen Tianzhen, Classification of meningeal tumors, Chinese Journal of Medical Computer Imaging 20033: 145~146
4. Chen Xingrong, Shen Tianzhen, Geng Daoying, etc., Meningioma Chinese Journal of Medical Computer Imaging 2003 (9) 3: 147~190
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Example 1, Figure 1,2 TRA, FSE:TR/TE=5300/80, lesion in the lateral ventricle with similar signal to the gray matter of the brain, with low signal points inside, visible tumor vessels, hydrocephalus.
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Example 1, Figure 3 and 4 show the same level of T1WI as Figure 1 and 2, respectively, FE3D: TR/TE=35/12 Figure 5 and 6 show the sagittal and coronal images. The lesion has a homogeneous signal and is similar to the gray matter of the brain.
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Example 1, Figure 7,8,9,10, Gd-DTPA enhanced scan. The lesion is clearly abnormally contrast-enhanced, with a more marked restrictive enhancement at the center and edges, and shows the tumor vessels and the relationship between the tumor vessels and the choroid plexus.
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Example 2 Figure 1, TRA, FSE: TR/TE=5300/80, Figure 2 FE3D at the same level as Figure 1: TR/TE=35/12, Figure 3 sagittal, Figure 4 coronal, the lesion has a homogeneous signal, comparable to the gray matter of the brain, irregular morphology, and no hydrocephalus.
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Example 2, Figure 15,16,17, Gd-DTPA enhancement scan, the lesion is clearly homogeneous with abnormal contrast enhancement, lobulated, and closely related to the choroid plexus vessels.