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Eduardo Carvalhal Ribas, Kaan Yağmurlu, Evandro de Oliveira, Guilherme Carvalhal Ribas and Albert Rhoton Jr.

OBJECTIVE

The purpose of this study was to describe in detail the cortical and subcortical anatomy of the central core of the brain, defining its limits, with particular attention to the topography and relationships of the thalamus, basal ganglia, and related white matter pathways and vessels.

METHODS

The authors studied 19 cerebral hemispheres. The vascular systems of all of the specimens were injected with colored silicone, and the specimens were then frozen for at least 1 month to facilitate identification of individual fiber tracts. The dissections were performed in a stepwise manner, locating each gray matter nucleus and white matter pathway at different depths inside the central core. The course of fiber pathways was also noted in relation to the insular limiting sulci.

RESULTS

The insular surface is the most superficial aspect of the central core and is divided by a central sulcus into an anterior portion, usually containing 3 short gyri, and a posterior portion, with 2 long gyri. It is bounded by the anterior limiting sulcus, the superior limiting sulcus, and the inferior limiting sulcus. The extreme capsule is directly underneath the insular surface and is composed of short association fibers that extend toward all the opercula. The claustrum lies deep to the extreme capsule, and the external capsule is found medial to it. Three fiber pathways contribute to form both the extreme and external capsules, and they lie in a sequential anteroposterior disposition: the uncinate fascicle, the inferior fronto-occipital fascicle, and claustrocortical fibers. The putamen and the globus pallidus are between the external capsule, laterally, and the internal capsule, medially. The internal capsule is present medial to almost all insular limiting sulci and most of the insular surface, but not to their most anteroinferior portions. This anteroinferior portion of the central core has a more complex anatomy and is distinguished in this paper as the “anterior perforated substance region.” The caudate nucleus and thalamus lie medial to the internal capsule, as the most medial structures of the central core. While the anterior half of the central core is related to the head of the caudate nucleus, the posterior half is related to the thalamus, and hence to each associated portion of the internal capsule between these structures and the insular surface. The central core stands on top of the brainstem. The brainstem and central core are connected by several white matter pathways and are not separated from each other by any natural division. The authors propose a subdivision of the central core into quadrants and describe each in detail. The functional importance of each structure is highlighted, and surgical approaches are suggested for each quadrant of the central core.

CONCLUSIONS

As a general rule, the internal capsule and its vascularization should be seen as a parasagittal barrier with great functional importance. This is of particular importance in choosing surgical approaches within this region.

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Thomas Frigeri, Eliseu Paglioli, Evandro de Oliveira and Albert L. Rhoton Jr.

OBJECT

Central Lobe consists of the pre- and postcentral gyri on the lateral surface and the Paracentral Lobule on the medial surface and corresponds to the sensorimotor cortex. The objective of the present study was to define the neural features, craniometric relationships, arterial supply, and venous drainage of the central lobe.

METHODS

Cadaveric hemispheres dissected using microsurgical techniques provided the material for this study.

RESULTS

The coronal suture is closer to the precentral gyrus and central sulcus at its lower rather than at its upper end, but they are closest at a point near where the superior temporal line crosses the coronal suture. The arterial supply of the lower two-thirds of the lateral surface of the central lobe was from the central, precentral, and anterior parietal branches that arose predominantly from the superior trunk of the middle cerebral artery. The medial surface and the superior third of the lateral surface were supplied by the posterior interior frontal, paracentral, and superior parietal branches of the pericallosal and callosomarginal arteries. The venous drainage of the superior two-thirds of the lateral surface and the central lobe on the medial surface was predominantly through the superior sagittal sinus, and the inferior third of the lateral surface was predominantly through the superficial sylvian veins to the sphenoparietal sinus or the vein of Labbé to the transverse sinus.

CONCLUSIONS

The pre- and postcentral gyri and paracentral lobule have a morphological and functional anatomy that differentiates them from the remainder of their respective lobes and are considered by many as a single lobe. An understanding of the anatomical relationships of the central lobe can be useful in preoperative planning and in establishing reliable intraoperative landmarks.