Septum Verum (true septum) is a region in the lower medial part of the telencephalon that separates the two cerebral hemispheres.

The human septum consists of two parts: The septum pellucidum (translucent septum), a thin membrane consisting of white matter and glial cells that separate the lateral ventricles, and the lower, precommisural septum verum, which consists of nuclei and grey matter.

The term is sometimes used synonymously with Area Septalis, to refer to the precommisural part of the lower base of the telencephalon. The Septum verum contains the septal nuclei, which are usually considered part of the limbic system.

The septum pellucidum and the subjacent septum verum form the medial wall of the frontal horn of the lateral ventricle. Both structures contain nerve fibers that were organized in 3 groups: 1) the precommissural fibers of the fornix; 2) the inferior fascicle; and 3) the superior fascicle of the septum pellucidum. The area directly rostral to the postcommissural column of the fornix consisted of macroscopically identifiable gray mattercorresponding to the septal nuclei. The histological examinations validated the findings of Barany et al. fiber dissections.

The nerve elements of the septum pellucidum as well as the subjacent septum verum were identified with fiber dissection and verified with histology for the first time. The septal nuclei located just anterior to the fornix and the precommissural fibers of the fornix should be preserved during endoscopic septum pellucidotomy. Considering the venous anatomy as well as the neural architecture of the septum pellucidum, the fenestration should ideally be placed above the superior edge of the fornix and preferably dorsal to the interventricular foramen ¹⁾.