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 sustaining life.
These structures require a space to exist, a space limited by the bone structure which protects the organ: the skull. And some of those structures could be really big, like with the cerebral cortex. Fortunately, throughout our development, the brain is compacted, causing the cerebral cortex to grow in such a way that it forms different folds (which gives the brain its characteristic appearance). And with these folds also appear the grooves between them. One of the most famous is the Silvio groove or side slit.
Cracks and grooves
Before we get into the details of what Silvio’s cleft is, we need to stop for a moment and look at the structure of our brain first. We will thus better understand the path that this fissure traces along the cerebral cortex.
Seen 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 various cracks, which are called cracks or grooves. The concave parts, those which protrude, are the turns or convolutions.
So it is seen as a groove or slot in this crack or hole left by the cerebral cortex when it collapses on itself during development and which, seen from the surface, gives an idea of what the limits of the lobes of the brain are.
Silvio’s slit: what is it and what areas does it separate?
Silvio’s side slit or groove is next to one of the most visible and recognizable cracks or grooves in the human brain. It is located in the lower part of the two cerebral hemispheres and then passes through a large part of the brain. This groove appears horizontally, being located in the naso-lambdoidea line.
This is one of the most relevant grooves because separates the temporal and parietal lobes and below the frontal from the temporal. We are facing the deepest fissure that exists in the whole brain, to the point where in its depths is the so-called fifth cerebral lobe: the insula. It also contains a transverse temporal gyrus, which participates in the auditory system.
It should also be noted that through it passes the middle cerebral artery, also called the silvane artery for this reason, which irrigates the different brain regions of the region.
This slit 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 have evolved as the fetus develops.
Silvio’s slit can be divided into several branches, More precisely in three main ones: ascending or vertical branch, horizontal branch and oblique trifurcation branch. The name of these gives an idea of their orientation.
Between the first and the second we can find the third frontal gyrus, and in particular the pars triangularis (Corresponding to Brodmann zone 45). In the horizontal branch, the pars orbitalis (zone 47) and the pars opercularis (corresponding to zone 44) between the oblique and vertical trifurcation branches. These areas are associated with the production of language.
Diseases and disorders with alterations of this cleft
Silvio’s cleft is a groove that all or almost all humans have. however, there are diseases in which this slit does not form properly or it is changed for some reason. Among them we can find examples in the following pathologies.
1. Alzheimer’s and other dementias
Patients with Alzheimer’s disease usually present throughout the development of their disease an enlargement of the Silvio cleft, Being this enlargement product of neuronal tissue degeneration. This anomaly can also be found in other dementias and neurodegenerative diseases, which over time kill nerve cells and make the brain appear withered, with large grooves and very pronounced folds. This means that its effects are not limited to the silvio crack, but are noticeable throughout the bark in general.
2. The absence of cerebral furrows: lysencephaly
Lysencephaly is an abnormality generated throughout neurodevelopment in which the brain appears smooth with or without some convolutions and cracks, alteration caused by a deficit or absence of neuronal migration or by an excess of it. 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 acting, in which no convolution or cerebral groove develops, and the incomplete or paquigiria in which there are some, although they are few and very wide. There is usually a bad coating of brain parenchyma in Silvio’s cleft.
In general, the prognosis is not good and the disease is associated with a short life expectancy, showing symptoms such as seizures, breathing problems and intellectual disability, although in some cases there is no major problems.
3. Opercular syndrome
Opercular or perisilvic syndrome, In which motor control problems or even paralysis appear in the facial area, is also related to the Silvio cleft during existing problems in the opercles, the areas of the brain that surround the Silvio cleft and correspond to the part not directly visible from the outside.
4. Cerebrovascular alterations
The middle cerebral artery passes through Silvio’s cleft. This is why changes in this area can also affect this part of the circulatory system, which is likely to cause problems such as aneurysms, bleeding or emboli.
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