Trigonal intraventricular meningioma

Clinical History

A 30 year old male patient presented with a long-standing history of headache and vertigo. Clinical examination revealed mild papilledema. No cranial nerve deficit was detected. Routine blood investigations were within normal limits.

Imaging Findings

MR imaging of the brain revealed a large well-circumscribed intraventricular mass, located in the trigone of right lateral ventricle. The mass was expanding and distorting the trigone and occipital horn of the right lateral ventricle. On T1-weighted MR images, the mass was isointense relative to the cortex. On T2-weighted MR images the mass was predominantly hypo to iso-intense to the cortex with few areas of subtle hyperintensity. Contrast-enhanced T1-weighted MR images demonstrated avid homogeneous enhancement of the mass. Mild perilesional vasogenic oedema was seen in the adjacent cerebral parenchyma with midline shift to the contralateral side. The third ventricle was being externally compressed by the mass with resultant upstream ventriculomegaly. Based upon the MR imaging findings the diagnostic possibility of intra-ventricular meningioma was considered which was confirmed on histopathology.

Discussion

Primary intraventricular meningiomas are notably rare with an incidence of 0.5-3% among all intracranial meningiomas. Most intraventricular meningiomas originate in the trigones of the lateral ventricles and the left lateral ventricle is relatively more frequently affected than the right. Less commonly, they may arise at the foramen of Monro, within the 3rd ventricle or, very rarely, in the 4th ventricle. They are believed to arise from the infolding of meningeal tissue during the formation of the choroid plexus (from the arachnoid cap cells). Majority of these tumours occur in patients older than 30 years and females are more frequently affected. Patients usually present with symptoms related to raised intracranial tension.

CT typically demonstrates a sharply demarcated hyperdense intraventricular mass. Calcification may be seen in up to 20-50% of cases. On MRI, lesions are typically hypo-to isointense on T1- and T2-weighted images relative to the cerebral cortex. Low signal intensity on T2-weighted images is one of the key features of meningioma. They characteristically show intense uniform enhancement due to their lack of blood-brain barrier. Cystic areas secondary to cystic degeneration or necrosis may occasionally be noted. Besides meningioma, there is a broad list of differentials for an intraventricular mass in an adult, which includes glioma (astrocytoma, subependymoma, giant cell astrocytoma), ependymoma, choroid plexus papilloma and metastasis. Although astrocytoma on MRI, may be indistinguishable from an intraventricular meningioma they are mostly seen in pediatric age group or young adults. On CT, astrocytoma appear as a cystic or hypodense solid mass. Subependymomas and central neurocytomas are usually found in the anterior portion of the lateral ventricle and typically demonstrate a heterogeneous cystic appearance. Subependymal giant cell astrocytomas are seen at the foramen of Monro and are characterized by frequent calcification, intense enhancement, and the presence of other tuberous sclerosis stigmata. Choroid plexus tumours such as choroid plexus papilloma, carcinoma, or metastasis demonstrate a heavily lobulated appearance and intense enhancement owing to their high vascularity. Ependymomas are typically located in the fourth ventricle, often partially calcified demonstrating heterogeneous signal on T1-weighted and hyperintense signal on T2-weighted images.

To conclude, meningiomas are the most common intraventricular tumor of the trigone to occur in adults. Besides meningioma, a wide range of neoplasms may arise within the ventricular cavity. This case illustrates the classic features of an intraventricular meningioma i.e a sharply circumscribed, intensely enhancing, T2-hypointense trigonal mass with mild perilesional oedema presenting in an adult patient.

Differential Diagnosis List

Final Diagnosis

Intraventricular meningioma

URL:	https://www.eurorad.org/case/8917
DOI:	10.1594/EURORAD/CASE.8917
ISSN:	1563-4086