Morphology and Hemispheric and Gender difference of the Anterior Ascending Ramus and the Horizontal Ascending Ramus of the Lateral Sulcus

Abstract Broca’s area is composed of the pars opercularis (PO) and the pars triangularis (PTR) of the inferior frontal gyrus，which was separated by the anterior ascending ramus of lateral sulcus (aals) and the horizontal ascending ramus of the lateral sulcus (hals). The morphometry of these two sulci maybe have potential effects on the various functions of Broca’s area. To explore the morphology variation, hemispheric and gender difference of these two sulci, so as to enable better understanding of their patterns and the functions of the Broca’s area. BrainVISA was used to reconstruct and parameterize these two sulci with 3D MR images of 90 healthy right-handed subjects. The 3D anatomic morphology of these two sulci was presented using 4 sulcal parameters, including average depth (AD), average width (AW), top length (TL) and bottom length (BL). The aals could be identified in 98.89% of the hemispheres, while the hals could be identified in 98.33%. The morphological patterns of these two sulci were categorized into four main types. There were no statistically significant interhemispheric and gender differences in the frequency of the morphological patterns. There was statistically significant interhemispheric difference in BL of the aals and AW of the hals. Significant gender differences were found in the bilateral AD of the aals and the BL and TL of the hals in right hemisphere. Our results will not only provide structural basis for the functional studies that related to Broca’s area, but also be helpful for the precise positioning of special structures in neurosurgery.