abnormal lateral ventricle morphology absent lateral ventricles 2014-03-19T14:29:20Z MP:0012680 MPheno.ontology absence of the cavity in each of the cerebral hemispheres derived from the cavity of the embryonic neural tube; lateral ventricles 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 csmith