Frontal Aslant Tract and Its Role in Language: A Journey Through Tractographies and Dissections.

BACKGROUND: The frontal aslant tract (FAT) is a bilateral tract located within each frontal lobe. It connects the supplementary motor area in the superior frontal gyrus with the pars opercularis in the inferior frontal gyrus. There is a new and broader conceptualization of this tract called the extended FAT (eFAT). The eFAT tract role is believed to be related to several brain functions, including verbal fluency as one of its main domains. METHODS: Tractographies were performed by using DSI Studio software on a template of 1065 healthy human brains. The tract was observed in a three-dimensional plane. The Laterality Index was calculated based on the length, volume, and diameter of fibers. A t test was performed to verify the statistical significance of global asymmetry. The results were compared with cadaveric dissections performed according to the Klingler technique. An illustrative case enlightens the neurosurgical application of this anatomic knowledge. RESULTS: The eFAT communicates the superior frontal gyrus with the Broca area (within the left hemisphere) or its contralateral homotopic area within the nondominant hemisphere. We measured the commisural fibers, traced cingulate, striatal, and insular connections and showed the existence of new frontal projections as part of the main structure. The tract did not show a significant asymmetry between the hemispheres. CONCLUSIONS: The tract was successfully reconstructed, focusing on its morphology and anatomic characteristics.

Three-Dimensional Anatomy of the Anterior Commissure: A Tractography and Anatomical Study.

BACKGROUND: The anterior commissure (AC) is one of the main commissural fibers of the brain. The commissural fibers are involved in bilateral integration and coordination of any normal brain activity. The AC is an important interhemispheric structure that forms a bidirectional communication channel between the frontal, temporal, parietal, and occipital lobes bilaterally. METHODS: In the present study, we focused on describing the morphology, relationships, and distribution of the AC using diffusion spectrum imaging-based fiber tracking. The tractograms were compared with the findings from gross anatomical dissection of the AC of adult brains. RESULTS: Our findings suggest that the AC found using tracking methods is larger than that found by dissection. CONCLUSIONS: The use of tractography added extensions to the main AC structure.