abnormal hippocampus morphology abnormal Ammon gyrus morphology Ammon gyrus dysplasia MP:0000815 MPheno.ontology abnormal Ammon horn morphology abnormal Ammon's horn morphology abnormal CA abnormal Cornu Ammonis morphology abnormal hippocampus proper morphology any structural anomaly of one or both of the two interlocking gyri of the hippocampus formation; a circonvolution of rhinencephalon, the grey substance of which is rich in big pyramidal neuronal cells