parenchyma with secondary extension into the ventricles, the authors found that the most common histologic diagnosis in adults was astrocytoma, followed by meningioma . In the pediatric age group, the most common diagnosis was subependymal giant cell astrocytoma. In another series , the most frequent tumor types were subependymal giant cell astrocy-toma, choroid plexus tumors, ependymoma and astrocytoma. The most common location for lateral ventricular tumors was the trigone (38%), followed by the cella media (33%) and the frontal horn (27%) .
Intraventricular meningioma, although rare, is a well circumscribed tumor, most often located in the trigone, and constitutes approximately 0.5-2% of all intracranial meningiomas
 (Figure 13.1). Approximately 80% occur in the lateral ventricles, more commonly in the left trigone, but can occur in the third ventricle, and less frequently in the fourth ventricle. Most patients present in the fourth to the sixth decades, and these tumors are more common in women. The intraventricular location of these slow-growing tumors provides a compensatory mechanism in the form of reserve space, which contributes to the delay in clinical demonstration of symptoms and signs. They may either arise from the choroid plexus and grow within the ventricle, or arise from the tela choroidea and grow partly within the ventricle and partly into the surrounding brain tissue. Imaging characteristics are similar to those of other menin-giomas, being sharply defined and globular.
Fig. 13.1.a Despite the large size of the tumor, the patient had minimum symptoms and presented with headaches. b Postoperative images after resection via the superior parietal lobule. Because of the location within the dominant hemisphere, a posterior middle temporal gyrus approach would carry risk of speech impairment.
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