Longitudinal striae of the human fornix: shape, relations and variations

Two pairs of sagittal longitudinal striae, medial and lateral, are slender bundles of fibers located on the dorsal surface of corpus callosum, situated deeply in the longitudinal fissure of telencephalon. Imbedded in the structure of tiny gyrus, indusium griseum, they are, in fact, supracallosal fibers of the fornix, previously called fornix longus.

Longitudinal striae were investigated in 25 fixed human brains obtained from autopsies. Macrodissection and morphometric methods were used in order to find out and analyze the appearance and gross morphological variability of longitudinal striae, as well as their inter-individual relations.

Lateral longitudinal striae were located along the sulci of corpus callosum. Medial striae were positioned along the sagittal midline and they were mostly individual. However, they were at times connected, spanned or duplicated. Longitudinal striae make a characteristic pattern on the dorsal surface of corpus callosum. A classification of striae is made on the basis of their appearance.

Although similar at first sight the striae, especially medial ones, have some individual features which make the pattern variable. Medial striae are more variable than the lateral ones. Perhaps functional neuroimaging and DT MRI will disclose the enigma of these striae.