Coming from the Latin word scissūra, the idea of fissure allows to refer to an opening or cleft that is registered in some structure. It can be a groove that occurs naturally or is caused by some type of injury or disease.
The concept of fissure is commonly used to refer to the folds found in the brain, cerebellum, and medulla oblongata. The intercerebral fissure, also called the interhemispheric fissure, divides the brain into two hemispheres that are linked to each other by the corpus callosum.
These hemispheres, in turn, are divided into lobes by other fissures. The Rolando fissure, in this setting, allows us to distinguish between the frontal lobe and the parietal lobe. The Sylvian fissure, meanwhile, separates the temporal lobe from the parietal lobe and the frontal lobe. The calcarine fissure, the fissure Broca, the superfrontal sulcus and simian sulcus are other fissures present in the brain.
In the cerebellum they are the longitudinal fissure, the horizontal fissure, the posterolateral sulcus and adoccipital sulcus, while in the medulla can recognize the rear half sulcus.
There are also fissures in other parts of the body beyond the head. Among them we can name the glottis fissure (in the throat), the corneal fissure (in the eye), the antitragohelicina fissure (in the ear) and many others.
Certain fissures are pathological and appear before the onset of certain disorders. This is the case of Harrison’s groove, which is seen with advanced rickets, and Liebermeister’s groove, produced by compression in the area of the ribs, for example.
About Silvio’s fissure
As evidenced a few paragraphs above, along with Rolando’s fissure, Silvio’s is one of the most important in the brain of our species, and in fact it is also among the easiest to see. It is located in the lower part of the two hemispheres, in the line known as the naso-lambdoid, and then it crosses almost the entire brain surface.
One of the reasons that make this fissure one of the most relevant in our anatomy is the fact that it separates the parietal and temporal lobes, as well as the temporal and frontal lobes in their lower part. Furthermore, there is no deeper cleft in the human brain; so much so that it houses the insula, the so-called fifth lobe of the brain, and the transverse temporal gyrus, which is involved in the hearing process, at the bottom of its walls.
Some diseases have the characteristic that the Silvio fissure does not form properly or that it is altered in some way. In Alzheimer’s disease, for example, throughout its development it causes the cleft to enlarge, as a result of the degeneration suffered by the neuronal tissue. This is not exclusive to this disease, but can also be seen in other neurodegenerative diseases and in some dementias.
On the other hand, there is lissencephaly, an abnormality that occurs during neuronal development and is characterized by the smooth appearance of the brain, as it causes it to have few or no furrows, due to an extreme percentage of neuronal migration: already be it its absence, a deficit or an excess of it.
The perisylvian syndrome carries certain motoros problems or cases of paralysis in the face, and this is because the parts of the brain surrounding the Sylvian fissure given developmental disorders.