A 54-year-old female presented with chronic headaches. Imaging showed an intraventricular mass in the right lateral ventricle that enhanced avidly and demonstrated restricted diffusion. Based on the imaging, meningioma was suspected. During surgery, the mass was resected and found to be attached to the choroid plexus. Pathology confirmed it was a grade 1 fibroblastic meningioma. Intraventricular meningiomas are rare, accounting for less than 1% of meningiomas, and usually occur in the lateral ventricles in patients aged 30-60 years old.

1. Harbor-UCLA Neuroradiology Case Conference Sahar Farzin, M.D. Dept. of Radiolgy, Harbor-UCLA Medical Center Peter Abasolo, M.D. Dept. of Pathology, Harbor-UCLA Medical Center

2. History: 54 year old female with chronic headaches

3. FLAIR Axial FLAIR images show a well circumscribed, homogenous, hyperintense lesion expanding the atrium of the right lateral ventricle.

4. Pre-Gadolineum Axial T1WIs show an intraventricular mass which is isointense to the normal gray matter. Post-Gd the lesion demonstrates “light bulb” avid enhancement. The atrium of the right lateral ventricle is enlarged around this mass. There is no evidence of hydrocephalus.

5. Sagital Pre- and Post-Gadolineum T1WIs show the avidly enhancing intraventricular tumor.

6. Coronal Post-Gd T1WI shows the well circumscribed, homogenously enhancing mass within the trigone of the right lateral ventricle. The curvilinear hyperintense structure lateral to the mass is the normal enhancing choroid plexus. The trigone is expanded around the mass.

7. Coronal T2WI. The intraventricular mass is hyperintense to intermediate signal intensity compared to the gray matter. The hyperintense CSF is seen outlining the tumor within the expanded ventricle.

8. (Left to right) DWI and ADC map images show true restricted diffusion within the intraventricular mass. Tumors with dense cellularity may show restricted diffusion.

10. Based on imaging findings the most likely diagnosis is meningioma

13. Pathology

14. H&E: The fibroblastic meningioma variant consists of spindle cells with indistinct borders and collagen

15. Epithelial Membrane Antigen (EMA) IHC Stain, an epithelial marker for meningiomas, is positive.

16. Ki-67 IHC Stain shows a low proliferation index of 1-2%

17. S-100 IHC Stain is negative. (S100 belongs to the family of calcium binding proteins and stains schwannomas, ependymomas, astrogliomas, almost all benign melanocytic lesions, melanomas and their metastases. This stain is negative in meningiomas.)

19. Intraventricular Meningiomas Less than 1% of meningiomas are intraventricular and 80% of those occur in the lateral ventricles. They are the most common trigonal mass in adults. Intraventricular meningiomas occur in patients older than 30 years of age and usually between 30-60 years. Females are more common than males by 2:1. The most common presenting symptoms are related to increased intracranial pressure and include headache, nausea, vomiting, contralateral sensory/motor deficits and homonymous hemianopsia. The imaging characteristics of intraventricular meningiomas are similar to their intraparenchymal counterparts. They are well-defined, globular masses that may show hyperattenuation compared to the brain parenchyma on CT and demonstrate avid enhancement following contrast administration. Calcifications are common in 50% of cases.