The Silvio aqueduct is a conduit or channel located in a structure of our brain called the midbrain. and the function is to transport, from one ventricle to another, the cerebrospinal fluid, which acts as a shock absorber and protects us from blows to the head, among other functions relevant to our body.
In this article, we explain what the Silvio aqueduct is, what are its characteristics, where it is located, what functions it performs, how it develops and what are the main disorders associated with a dysfunction of this brain structure.
What is the Silvio aqueduct?
In neuroanatomy, it is known as the Silvio aqueduct, cerebral aqueduct, or mesencephalic aqueduct in the duct located in the midbrain that is responsible for connecting the third and fourth ventricles of the brain and through which cerebrospinal fluid passes (CSF) that permeates the brain and spinal cord.
CSF is a liquid substance that performs basic functions in our nervous system, including: acting as a protector against traumatic brain injury; provide hydropneumatic support; eliminate residual metabolites from the nervous system; and act as a homeostatic mechanism when certain hormonal imbalances occur in the body.
For the moment, the name of Silvio aqueduct is in disuse and in the current anatomical nomenclature, the name given to this cerebral structure is aqueduct of the mesencephalon or simply cerebral aqueduct. However, throughout this article we will be using the term Silvio aqueduct to refer to this one.
Location and structure
The Silvio Aqueduct is located inside the midbrain or midbrain, one of the parts that make up the brainstem. This brain structure is located above the protrusion or bridge of Varolio and below the diencephalon (Composed of the thalamus and hypothalamus, among other structures), and is made up of the tectum (or roof), located in the dorsal part; and the tegmentum (or integument), located just below the tectum.
The midbrain or midbrain is made up of several neural nuclei: The periaqueductal gray matter, involved in the treatment of pain or threatening stimuli; the red nucleus, which controls various motor processes; and the substantia nigra, a component of the basal nuclei whose functions are related to the mechanisms of motor control, learning and reward.
The Silvio aqueduct, as we mentioned at the beginning of the article, is a channel that communicates the third and fourth ventricles, in a system of four chambers or ventricles. The two lateral ventricles are located along the cerebral hemispheres and connect to the third ventricle through the interventricular hole or Monroe.
As for the third ventricle, it should be noted that it is a cavity located in the midline of the brain and delimited on each side by the thalamus and the hypothalamus. In its front part, it communicates, as we have mentioned, with the lateral ventricles and, in the rear part, with the aqueduct of Silvio.
For its part, the fourth ventricle is the one that is located at a level lower than the four brain ventricles. It extends from the Silvio aqueduct to the central channel of the upper end of the spinal cord, with which it communicates through several orifices: the Luschka holes, located on the sides; and the Magendie hole, located in the center and between the two Luschka holes.
Characteristics and development
The Silvio aqueduct, as the name suggests, is a chain or cerebrospinal fluid irrigation system that connects the third and fourth ventriclesAnd that, along with the lateral ventricles, constitutes the ventricular system that protects the brain, among other functions.
The development of the ventricular system occurs in parallel with the rest of the central nervous system. The cerebral ventricles are derived from the embryonic neuroepithelium. The ventricles, Silvio’s aqueduct, and the central duct of the spinal cord are lined with an epithelial layer of cubic and columnar cells, called the ependymal.
From the fifth week of embryonic development, the encephalic vesicles are differentiated into: telencephalon, diencephalon, midbrain, metencephalon and myelencephalon. These vesicles are hollow inside and hold their cavities until their development is complete. in adulthood: what we call the cerebral ventricles.
By the sixth week, the division of the cerebral vesicles is clearer; the forebrain has already been differentiated into telencephalon and diencephalon. The midbrain, on the other hand, has not divided, and its larger cavity gradually narrows in the first stages, at the same time as the Silvio aqueduct is formed, which communicates the third with the fourth ventricle.
The middle or midbrain is the structure that undergoes the least change during development, except for its most complete part. Finally, the length that reaches the aqueduct of Silvio is about 18 millimeters.
Hydrocephalus is a group of diseases caused by an increase in cerebrospinal fluid (CSF) inside the cranial cavity. Its incidence is 1 or 2 cases per 1000 births and occurs more frequently due to congenital than acquired causes. In cases of congenital hydrocephalus, teratogenic factors, malnutrition, toxins, etc. can have an influence.
There are three main types of hydrocephalus: communicable or non-obstructive, which occurs when the absorption of CSF is not adequate; non-communicating or obstructive ones, which occur when the flow of CSF is blocked in one or more channels of those connecting some ventricles to others; and normotensives, in which an increase in CSF in the ventricles is generated, with a slight increase in intracranial pressure.
One of the most common disorders associated with damage or obstruction of the Silvio aqueduct is known as hydrocephalus due to congenital waterworks stenosis (HSAS). This disease, associated with a phenotype that is part of the clinical spectrum of X-linked L1 syndrome, causes severe obstructive hydrocephalus, usually prenatal onset, which produces signs of intracranial hypertension, thumb abduction, symptoms of spasticity. and severe intellectual disability.
In children, one of the most common symptoms involves a rapid increase in the circumference or size of the head. Other autonomic or somatic symptoms may also occur, including vomiting, irritability, drowsiness, and seizures.
Although the consequences of hydrocephalus vary from patient to patient depending on age, disease progression, and individual differences in tolerance to CSF, it should be noted that hydrocephalus due to Silvio’s aqueduct stenosis represents the more severe end of the spectrum and has an unfavorable prognosis. .
- Carlson, BM (2005). Human embryology and developmental biology. Elsevier,.
- López, LP, Pérez, SM and de la Torre, MM (2008). Neuroanatomy. Pan American Medical Ed.