abnormal diencephalon morphology abnormal hypothalamus morphology any structural anomaly of the ventral part of the diencephalon extending from the region of the optic chiasm to the caudal border of the mammillary bodies and forming the inferior and lateral walls of the third ventricle; this region regulates the autonomic nervous system via hormone production and release hypothalamus dysplasia MP:0000837 MPheno.ontology abnormal limbic system morphology