A ínsula e o conceito de bloco cerebral central

Abstract

RESUMO -A caracterização anatômica de regiões encefálicas topograficamente bem definidas é particularmente útil para a prática neurocirúrgica por propiciar melhor compreensão da tridimensionalidade das suas estruturas e das lesões que as acometem, e por incitar uma maior sistematização dos seus acessos cirúrgicos. Neste sentido, se destaca no interior de cada hemisfério cerebral, um verdadeiro bloco único composto externamente pela ínsula, internamente pelos núcleos da base e tálamo, e que abriga no seu interior a cápsula interna. Com uma conformação predominantemente biconvexa e disposto entre a cisterna silviana e as cavidades ventriculares supratentoriais, esse bloco cerebral central morfologicamente se caracteriza como uma cabeça de cada metade do tronco encefálico, encoberta por todo o manto neocortical do seu hemisfério ao qual se une através de verdadeiros istmos constituídos pelos prolongamentos das diferentes partes da cápsula interna. Anteriormente e sob o sulco limitante anterior da ínsula se dispõem as fibras que compõem o ramo anterior da cápsula interna, superiormente e sob o seu sulco limitante superior se dispõem as fibras restantes do ramo anterior e as do joelho e do ramo posterior, entre as quais se destacam em importância funcional as fibras piramidais córtico-espinhais, e sob o sulco limitante inferior da ínsula se dispõem as partes retro e sub-lentiformes da cápsula interna, que englobam as radiações auditiva e visual. Lateralmente o bloco cerebral central tem a ínsula como um verdadeiro escudo externo das principais estruturas cerebrais subcorticais. As escolhas dos acessos microneurocirúrgicos às lesões relacionadas com o bloco cerebral central devem ter como maior preocupação as suas relações topográficas com o tálamo e com as fibras da cápsula interna. PALAVRAS-CHAVE: ínsula, núcleos da base, tálamo, cápsula interna, neuroanatomia, microcirurgia. The insula and the central core conceptABSTRACT -The caracterization of well defined and circumscribed brain regions is particularly useful for the neurosurgical practice once it enhances the tridimensional understanding of its structures and related lesions, and because it induces the development and the utilization of more standard microneurosurgical approaches. In this direction, it is noteworthy that each cerebral hemisphere harbors an evident central core constituted externally by the insula, internally by the basal ganglia and the thalamus, and with the internal capsule within. With a biconvex configuration when seen from above, and located between the sylvian cistern and the supratentorial ventricular cavities, morphologically this central core resembles a head of each brainstem half top, covered by the neocortical mantle of its hemisphere. The central core is attached to the rest of the cerebral hemisphere by isthmi constituted by the different internal capsule fibers. Anteriorly and under the anterior limiting sulcus of the insula there are fibers of the internal capsule anterior limb, superiorly and under the superior limiting sulcus ...

Microsurgical anatomy of the central core of the brain

“…The temporal stem can be divided into an anterior and medial component, which resembles an anterior temporal peduncle (formed by the ventral amygdalofugal fibers, UF, anterior aspects of the IFOF and of the anterior commissure, and the superior extension of the amygdala toward the globus pallidus), and a posterior and lateral component, constituted by the fibers that pass underneath the ILS between the tip of the temporal horn and LBG (posterior aspects of IFOF and anterior commissure, and optic radiation fibers). 32,35 Based on subcortical mapping by electrical stimulation during awake neurosurgical procedures, Duffau 6 proposed the existence of a ventral and a dorsal stream associated with language, where the former is related to the UF and the IFOF and the latter to the superior longitudinal fascicle and, most importantly, to its arcuate fasciculus component. The ventral stream is present inside the central core and is associated with the semantic components of language; 9,10 the dorsal stream is outside the central core and is related to phonemic components of language.…”

“…4 From a neurosurgical standpoint, the central core concept of the brain is particularly justified since the complexity and possible morbidities of surgery in this region are very relevant. Even though a few authors have already described the central core as a distinct region, 4,30,35 the current study was undertaken to better define its limits, describe its contents, and clarify the complex relation between its structures. We also propose a subdivision of the central core into quadrants with the aim of making operations involving this region safer and more precise.…”

Gross Anatomy of the Human Insula

“…From a topographic point of view, the insula is considered the outer shield of a well-defined cerebral central core [8,5,9]. Attached to the upper portion of each half of the midbrain, the central core corresponds in each hemisphere to the insula, basal nuclei, thalamus and internal capsule.…”

Dissection technique for the study of the cerebral sulci, gyri and ventricles

“…The superior (SFS) and inferior frontal sulci (IFS) as the superior (SFG), middle (MFG) and inferior (IFG) frontal gyri must be identified. At the left side, the 3 divisions of inferior frontal gyrus between the anterior ascending and anterior horizontal ramus of the lateral sulcus are found (pars orbitalis, triangularis and opercularis) and its correspondence with the insula limits must be searched for [2][3][4][6][7][8] . The relations of the superficial structures with the deep ones, as the place of foramen of Monro according to the superficial landmarks must always be looked for is called intra-parietal point and takes you to the atrium of ventricles 9,10 .…”

“…The circular sulcus from the insula, insular gyri, central sulcus of the insula and its limits must be identified. The relation from the insular region to the ventricular, basal ganglia and different portions of the internal capsule is one of the most important elements to understand the third dimension view of the superficial and deep supratentorial structures 2,4,7 (Fig 2B).…”