abnormal hippocampal commissure morphology absent hippocampal commissure MP:0008223 MPheno.ontology absence of the triangular subcallosal plate of commissural fibers resulting from the converging of the right and left fornix bundles which exchange numerous fibers and which curve back in the contralateral fornix to end in the hippocampus of the opposite side absent commissure fornicis absent commissure hippocampi absent commissure of fornix absent delta fornicis absent hippocampus commissure absent ventral hippocampal commissure absent vhc