The ventricles are surrounded by a layer of ependymal and  subependymal plate formed by glial cells. Such layers give origin to ependymomas, subependymomas and subependymal giant cell astrocytomas.  The septum pellucidum is also lined by glial cells and residual neuronal precursor cells, and it gives rise to the central neurocytoma. The choroid plexus is the most vascularized portion of the ventricular system and produces the cerebrospinal fluid. Primary neoplasias of this tissue are highly vascularized and are commonly associated with hydrocephalus due increased production of cerebrospinal fluid. Intraventricular tumors can obstruct CSF pathways, leading to hydrocephalus.