Silvio fissure (brain): what it is, functions and anatomy

Our brain is one of our most important and complex organs, being full of different structures, areas and regions of great importance that govern different basic aspects for the maintenance of life.

These structures require a space to exist, a space that is limited by the bone structure that protects the organ: the skull. And some of these structures could be really large, as is the case with the cerebral cortex. Fortunately, throughout our development, the brain compacts, growing the cerebral cortex. in such a way that it forms different folds (which gives the brain its characteristic appearance). And with these folds the grooves between them also appear. One of the most famous is the lateral sulcus or the Silvio fissure.

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Fissures and grooves

Before going into detail about what Silvio's fissure is, we must stop for a moment and first consider how our brain is structured. In this way we will better understand the path that this cleft traces along the cerebral cortex.

Viewed from the outside, the brain appears as a relatively compact mass, the cerebral cortex being full of folds in such a way that the whole of it fits inside the skull. The fact that these folds exist also generates the existence of different fissures, which are called fissures or grooves. The concave parts, the ones that stand out, are the turns or convolutions.

Thus, a sulcus or cerebral fissure is considered to be that cleft or gap left by the cerebral cortex as it folds back on itself during development and that, seen from the surface, gives an idea of ​​what are the limits of the lobes of the brain.

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Silvio's fissure: what is it and what areas does it separate?

Silvio's fissure or lateral sulcus is together with Rolando's one of the most visible and recognizable fissures or furrows of the human brain. It sits at the bottom of the two brain hemispheres to later cross a large part of the brain. Said groove appears horizontally, being located in the naso-lambdoid line.

It is one of the most relevant grooves, since separates the temporal and parietal lobes and in its lower part the frontal of the temporal. We are facing the deepest cleft that exists in the entire brain, to the point that in its depths the so-called fifth brain lobe hides: the insula. It also contains the transverse temporal gyrus, which is involved in the auditory system.

It should also be noted that the middle cerebral artery, also called the sylvan artery, passes through it for this reason, it irrigates the different brain regions in the area.

This fissure is one of the first to appear throughout our development, being already visible in fetal development. Specifically, it can often be seen from the fourteenth week of gestation. Its morphology and depth will evolve according to the development of the fetus.

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Branches

Silvio's fissure can be divided into several branches, specifically in three main ones: ascending or vertical branch, horizontal branch and oblique trifurcation branch. The name of these gives an idea about their orientation.

Between the first and the second we can find the third frontal gyrus, and specifically the pars triangularis (corresponding to the Brodmann area 45). In the horizontal branch the pars orbitalis (area 47) and the pars opercularis (corresponding to area 44) between the oblique and vertical trifurcation branches. These areas are associated with the production of language.

Diseases and disorders with alterations in this fissure

Silvio's fissure is a groove that all or practically all human beings have. However, there are diseases in which this fissure does not form correctly or it is altered for any reason. Among them we can find examples in the following pathologies.

1. Alzheimer's and other dementias

Alzheimer's patients usually present throughout the development of their disease an enlargement of Silvio's fissure, said enlargement being the product of the degeneration of the neuronal tissue. This anomaly can also be found in other dementias and neurodegenerative diseases, which over time kill nerve cells and leaving the brain with a withered appearance, with large furrows and very folds. pronounced. This means that its effects are not limited to the sylvian fissure, but are noticed throughout the cortex in general.

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2. The absence of brain sulci: lissencephaly

Lissencephaly is an abnormality generated throughout neurodevelopment in which the brain appears smooth and either without or with few convolutions and fissures, alteration caused by a deficit or absence of neuronal migration or by an excess of this. This phenomenon can have genetic causes or be due to alterations produced during embryonic development.

It can be presented in two ways: the complete one, also called agiria, in which neither convolutions or cerebral sulci, and the incomplete or pachygyria in which there are some, although they are few and very spacious. There is usually a poor covering of brain parenchyma in Silvio's fissure.

In general, the prognosis is not good, and the disease is associated with a short life expectancy, presenting symptoms such as seizures, respiratory problems and intellectual disability, although in some cases there are no major problems.

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3. Opercular syndrome

The opercular or perisylvian syndrome, in which motor control problems appear or even paralysis in the area of ​​the face, it is also linked to Silvio's fissure when there are problems in the operculums, the brain areas that surround Silvio's fissure and correspond to the part not directly visible from the Exterior.

4. Cerebrovascular disorders

The middle cerebral artery passes through the Silvio fissure. That is why alterations in this area can also affect this part of the circulatory system, which is capable of generating problems such as aneurysms, bleeding or strokes.

Bibliographic references:

• Chi J.G.;, Dooling, E.C. & Gilles, F.H. (January 1977). "Gyral development of the human brain". Annals of Neurology 1 (1): 86-93.
• Kandel, E.R.; Schwartz, J.H.; Jessell, T.M. (2001). Principles of Neuroscience. Madrid: MacGrawHill.
• Santos, L. (2000). Synthesis of human anatomy. Conceptual keys and Atlas of basic diagrams. Editions University of Salamanca.