Body of fornix

The body of the fornix is the central part of the fornix, formed where the right and left crura converge near the midline. It is approximately triangular, being narrow anteriorly and broader posteriorly, and arches over the thalamus and beneath the septum pellucidum. Anteriorly, it divides into the right and left columns of the fornix.

Its superior surface is related medially to the septum pellucidum anteriorly and the corpus callosum posteriorly. Laterally, the superior surface contributes to the floor of the lateral ventricle and is covered by ventricular epithelium. Its lateral margin is closely related to the choroid plexus.

The inferior surface rests on the tela choroidea of the third ventricle, which separates the fornix from the roof of the third ventricle and the medial parts of the superior surfaces of the thalami.

Posteriorly, transverse commissural fibres between the two sides form the forniceal (hippocampal) commissure, also termed the psalterium, connecting the crura of the hippocampal formations across the midline.