Central Core Subdivision. A, In this lateral view, the central core was detached from the other cerebral lobes by a deep cut made along the insular sulci and the limbic structures were removed by opening the choroidal fissure. The central core can be subdivided into quadrants by a vertical line (green) and a horizontal line (blue), both of them meeting at the lateral projection of the foramen of Monro. The vertical line is drawn between the most anterior aspects of the precentral sulcus and the cerebral peduncle, representing the anterior limit of the pyramidal tract, and informs the surgeon that the internal capsule present deep inside the posterior quadrants has the pyramidal tract among its fibers. The horizontal line drawn by connecting the floor of the anterior horn of the lateral ventricle to the lateral geniculate body informs the surgeon that approaches to lesions that are lateral to the anterior horn and body of the lateral ventricle have to be made superiorly to this line, approaches lateral to the third ventricle should be at the posteroinferior quadrant, and approaches to the anteroinferior quadrant will be at the anterior perforated substance region. B, In this superior view of the central core, a line (orange) was drawn along the internal capsule (superiorly) and the lenticulostriate arteries (deep). This line represents a parasagittal plane that should not be crossed during surgeries due to the high functional eloquence of its structures: lesions located laterally should be approached by transinsular lateral approaches, and lesions located medially are better approached by medial routes. (Images courtesy of E de Oliveira)