Hippocampal malrotation, also termed incomplete inversion of the hippocampus or hippocampal malformation, is an increasingly recognized neuroimaging finding of undetermined clinical significance. It is characterized by features including (i) Round or pyramidal shape instead of ovoid shape; (ii) Medial position of the hippocampus on the hippocampal sulcus; (iii) The collateral sulcus is excessively deep or verticalized; (iv) Fimbria located medial to the hippocampus; (v) Small or displaced fornix; (vi) Enlarged temporal horn and empty choroid fissure; (vii) Thickened subiculum; (viii) Reduced upper horizontal portion of the parahippocampal gyrus. [from
HPO]