Specific Imaging Findings

Intraventricular meningiomas typically arise from the trigone in the posterior aspect of the lateral ventricles, more commonly on the left side, characteristically with a lobulated contour. Similar to meningiomas in other locations, the masses are hyperdense to calcified on non-enhanced CT. The tumors are usually homogenous with dense contrast enhancement. On MR imaging they show iso- to hyperintensity compared to the brain gray matter and are usually of low T1 and T2 signal intensity. Similar to meningiomas in other locations, very high cerebral blood volume is found on perfusion studies and MR spectroscopy may show the presence of alanine. These neoplasms may also arise around the foramina of Monro as well as within the third and fourth ventricles. Irregular lobulations, necrotic (nonenhancing) portions, and a combination of high T2 signal (bright on FLAIR images) and low diffusion values (dark on ADC maps) suggest higher-grade (atypical or malignant) subtypes, which are relatively common in intraventricular meningiomas.

Pertinent Clinical Information

The tumors often grow slowly to a substantial size before they become symptomatic. The most common presenting symptoms and signs are headache, mental change, hemianopsia, and vertigo. Total surgical removal can be achieved in most cases.

Differential Diagnosis

Choroid Plexus Papilloma (148)

1. • heterogenous with prominent vascular structures (flow-voids)

2. • characteristically arise at the trigone of lateral ventricles in children and in the fourth ventricle in adults