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 bony structure that protects the organ: the skull. And some of these structures could be really big, like the cerebral cortex. Fortunately, throughout our development, the brain becomes compact, growing the cerebral cortex 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 lateral furrow or Silvio’s fissure .

Splits and grooves

Before we go into detail about what Silvio’s cleft is, we must stop for a moment and first consider how our brain is structured. In this way we will better understand the path 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 so that the whole of it fits inside the skull. The fact that these folds exist also generates the existence of different indentations, which are called clefts or furrows. The concave parts, those that protrude, are the turns or convolutions.

Thus, a cerebral furrow or cleft is considered to be that which leaves the cerebral cortex when folded back on itself during development and which, seen from the surface, gives an idea of the limits of the brain’s lobes.

The Silvio’s cleft: what is it and what areas does it separate?

The Silvio’s fissure or lateral furrow is, together with Rolando’s, one of the most visible and recognisable fissure or furrow in the human brain. It is located in the lower part of the two cerebral hemispheres and then crosses over a large part of the brain. This furrow appears horizontally, being located in the naso-lambdoid line.

This is one of the most relevant grooves, since separates the temporal and parietal lobes and in its lower part the front of the temporal . This is the deepest fissure that exists in the entire brain, to the point that in its depths hides the so-called fifth cerebral lobe: 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 known as the sylvan artery for this reason, which irrigates the different brain regions in the area, passes through it.

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

Branches

Silvio’s fissure can be divided into several branches , specifically into 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 front circumvolution, and specifically the pars triangularis (corresponding to the area of Brodmann 45). In the horizontal branch the pars orbitalis (the area 47) and the pars opercularis (corresponding to the area 44) between the oblique and vertical trifurcation branches. These areas are associated with language production.

Diseases and disorders with alterations in this cleft

The Silvio’s fissure is a furrow that all or practically all human beings possess. However, there are diseases in which this fissure is not formed correctly or is altered for some reason. Among them we can find examples in the following pathologies.

1. Alzheimer’s and other dementias

Patients with Alzheimer’s usually present an enlargement of Silvio’s cleft throughout the development of their disease , this enlargement being the product of the degeneration of the neuronal tissue. This abnormality can also be found in other dementias and neurodegenerative diseases, which over time kill nerve cells and cause the brain to appear withered, with large grooves and very pronounced folds. This means that their effects are not limited to the sylvatic cleft, but are felt throughout the entire bark in general.

2. The absence of brain grooves: lysencephaly

Lysencephaly is an anomaly generated throughout neurodevelopment in which the brain appears smooth and either without or with few convolutions and clefts, alteration caused by a deficit or absence of neuronal migration or by an excess of it . This phenomenon may 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 circumvolutions nor cerebral furrows are developed, and the incomplete or pachygiria in which some, although few and very extensive, do exist. There is usually a deficient covering of the cerebral parenchyma in Silvio’s fissure.

Generally 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.

3. Opercular syndrome

The opercular or perisilvian syndrome , in which motor control problems or even paralysis appear in the area of the face, is also linked to Silvio’s fissure as there are problems in the operculi, the brain areas that surround Silvio’s fissure and correspond to the part not directly visible from the outside.

4. Cerebrovascular disorders

The middle cerebral artery runs through Silvio’s 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, hemorrhages or embolisms.

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. Claves conceptuales y Atlas de esquemas básicos. Editions University of Salamanca.