Morphometry, Asymmetry and Variations of the Sylvian Fissure and Sulci Bordering and Within the Pars Triangularis and Pars Operculum: An Autopsy Study

Objective: Speech and Language, one of the most lateralized of all cerebral functions is located within the pars opercularis (PO) and pars triangularis (PT). There is also inter-hemispheric variability of the sulcal contours bordering these areas. The study was undertaken to note the morphometry, asymmetry and variations of the Sylvan fissure (SF), and the sulci bordering and within the PO and PT. Materials and Methods: An adult autopsy cadaveric study was carried. The measurements made amongst others, included fronto-occipital cerebral length, cerebral width, Sylvian fissure length, and anterior Sylvian point (ASP) to inferior Rolandic point distance. The PT and PO were also studied. Results: Sixty-two adult cadaveric hemispheres were studied. The SF length on the right (mean=84.3mm, median=88mm) was significantly shorter than that on the left (mean=89.4mm, median=92.0mm) (p=0.037). The anterior ascending and anterior horizontal rami of the SF arose from the ASP and either divides at this point (43 hemispheres, 69.4%) or have a common short stem before separating distally giving a Y-shape configuration. The triangularis sulcus was noted in 49 hemispheres (79%) while the diagonal sulcus was noted in 26 hemispheres (41.9%). Conclusion: The left SF was significantly longer than the right and both were positively correlated. The presence of the triangularis sulcus was not dependent on the side (p=0.348) or gender (0.622) unlike the diagonal sulcus was side dependent (p=0.000).