has part has part has_part characteristic of has modifier abnormal fourth ventricle morphology absent fourth ventricle MPheno.ontology absent ventricle of rhombencephalon 2014-03-19T14:24:13Z absence of the irregularly shaped cavity in the rhombencephalon, normally located between the medulla oblongata, the pons, and the isthmus in front, and the cerebellum behind; the fourth ventricle is continuous with the central canal of the cord below and with the cerebral aqueduct above, and through its lateral and median apertures it communicates with the subarachnoid space absent IVth ventricle absent 4th ventricle absent ventriculus quartus csmith absent rhombencephalic ventricle MP:0012678 abnormal absent fourth ventricle