Neurosurgical anatomy of the opercular-insular region

Abstract

OBJECTIVE: The purpose of this work was to study the anatomy of the opercular-insular region, namely of the lateral sulcus (Sylvian fissure) and the opercula and the relation to the branches of the middle cerebral artery (MCA). PATIENTS AND METHODS: The length of the three rami of the lateral sulcus and the thickness of the opercula were measured in twenty formalin-fixed adult brain hemispheres. The branching pattern and origin of the cortical branches of the MCA were characterized. The data obtained was statistically analyzed. RESULTS: The posterior ramus was the longest of the rami of the lateral sulcus (p<0.001). There was a statistically significant increase in the thickness of the opercula in an anterior-posterior direction (p<0.001). MCA bifurcation was found in 85% and trifurcation in 15% of the hemispheres. Trunk dominance was significantly more frequent on the right MCA when compared to the left MCA (88.9% vs. 37.5%, p=0.05). The orbitofrontal, prefrontal, precentral, central, and anterior parietal arteries arose more commonly from the superior trunk. The anterior temporal, middle temporal, posterior temporal, temporo-occipital, angular, and posterior parietal arteries arose more commonly from the inferior trunk. When present, the middle trunk gave rise to the precentral, central, anterior parietal, and posterior parietal arteries. We found early branches in 80% of the hemispheres. CONCLUSIONS: This study contributed to improving the anatomical understanding of the lateral sulcus and of the structures located in its depth by using quantitative morphometric methods. These new data may allow neurosurgeons to optimize the surgical approach to this region.