abnormal lateral ventricle morphology enlarged lateral ventricles MP:0008535 MPheno.ontology increased size of the cavity in each of the cerebral hemispheres derived from the cavity of the embryonic neural tube; they are separated from each other by the septum pellucidum, and each communicates with the third ventricle by the foramen of Monro, through which also the choroid plexuses of the lateral ventricles become continuous with that of the third ventricle enlarged brain ventricles