has part has part has_part characteristic of has modifier abnormal fourth ventricle morphology dilated fourth ventricle 4th ventricle dilation dilated rhombencephalic ventricle dilated 4th ventricles rhombencephalic ventricle dilation fourth ventricle dilation the luminal space of the fourth ventricle is increased in volume or area, usually with an increase in contained fluid, in the irregularly shaped cavity in the rhombencephalon, between the medulla oblongata, the pons, and the isthmus in front, and the cerebellum behind; it 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 dilated fourth ventricles MP:0000829 dilated IVth ventricles dilated ventriculus quartus dilated IVth ventricle dilated 4th ventricle dilated ventricle of rhombencephalon dilated rhombencephalic ventricles IVth ventricle dilation ventriculus quartus dilation MPheno.ontology dilated brain ventricle abnormal dilated fourth ventricle