Meningiomas of the velum interpositum: surgical considerations.

Meningiomas of the third ventricle are a rare subtype of pineal region tumor that arise from the posterior portion of the velum interpositum, the double layer of pia mater that forms the roof of the third ventricle. The authors review the literature concerning these meningiomas and present a case in which the lesion was resected via the supracerebellar-infratentorial approach. The relationship of the tumor to the deep venous system and the splenium of the corpus callosum guides the selection of the most advantageous surgical approach. Posterior displacement of the internal cerebral veins demonstrated on preoperative imaging provides a strong rationale for use of the supracerebellar-infratentorial approach.