Fiber dissection anatomy of the dorsal and ventral language pathways at the temporo–parieto–occipital junction: Implications for fiber separation surgery

Abstract

Aim: The temporo–parieto–occipital junction (TPOJ) represents a critical convergence zone of the dorsal and ventral language pathways. Preservation of these tracts is essential during surgery for lesions involving this region. The aim of this study is to define the microsurgical anatomy of the dorsal and ventral language pathways at the TPOJ using the fiber dissection technique and to propose a surgical strategy based on the principles of fiber separation.Materials and Methods: Three formalin-fixed adult human cadaveric brains (six hemispheres) and two silicone-injected adult human cadaveric heads (four sides) were prepared using the Klingler fiber dissection technique. Stepwise microscopic dissections were performed from the cortical surface toward the deep white matter. The spatial relationships of the superior longitudinal fasciculus (SLF II–III), arcuate fasciculus (AF), inferior fronto-occipital fasciculus (IFOF), middle longitudinal fasciculus (MdLF), and extreme capsule (ExtC) were analyzed. Special attention was given to the depth, orientation, and natural separation planes between the dorsal and ventral language pathways.Results: The dorsal language system, mainly composed of SLF II–III and the arcuate fasciculus, was identified in all dissections as a superficial-to-intermediate layer beneath the U-fibers. The ventral language pathways, including the IFOF, MdLF, and extreme capsule system, were observed in deeper and more medial planes throughout the dissections. Between the dorsal and ventral systems, a distinct separation corridor was consistently identified, particularly along the interface between the arcuate fasciculus and the IFOF, across different cadaveric specimens. This corridor corresponded to a potential surgical plane for fiber separation techniques.Conclusions: At the TPOJ, the dorsal and ventral language pathways demonstrate a layered anatomical organization with distinct separation planes. Recognition of these natural separations may contribute to the development of fiber-preserving microsurgical strategies.