Silvio aqueduct: characteristics of this cerebral canal

Silvio's aqueduct is a conduit or channel located in a structure of our brain called the midbrain. and whose 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 important functions for our organism.

In this article we explain what the Silvio aqueduct is, what its characteristics are, where it is located, what functions performs, how it develops and what are the main disorders associated with a malfunction of this structure cerebral.

• Related article: "Parts of the human brain (and functions)"

What is the Silvio aqueduct?

In neuroanatomy, it is known as the aqueduct of Silvio, the cerebral aqueduct, or the aqueduct of the midbrain to the duct located in the midbrain that is responsible for connecting the third and fourth ventricle of the brain, and through which the cerebrospinal fluid passes (CSF) that permeates the brain and spinal cord.

CSF is a liquid substance that performs basic functions in our nervous system, among which are: acting as a protector against head injuries; provide hydropneumatic support; remove residual metabolites from the nervous system; and act as a homeostatic mechanism when certain hormonal imbalances occur in the body.

Currently, the name Silvio aqueduct is in disuse and In the current anatomical nomenclature, the name given to this brain structure is the midbrain aqueduct or, simply, the cerebral aqueduct.. However, throughout this article we will use the term Silvio aqueduct to refer to it.

• You may be interested in: "Cerebrospinal fluid: composition, functions and disorders"

location and structure

The Silvio aqueduct is located within the midbrain or midbrain, one of the parts that make up the brainstem. This brain structure is located above the pons or pons and below the diencephalon. (composed of the thalamus and hypothalamus, among other structures), and is integrated by the tectum (or roof), located in the dorsal part; and the tegmentum (or integument), located just below the tectum.

The midbrain or mesencephalon is made up of various neuronal nuclei.: the periaqueductal gray matter, involved in the processing of pain or threatening stimuli; the red nucleus, which controls various motor processes; and the substantia nigra, a component of the basal ganglia whose functions are related to motor control, learning, and reward mechanisms.

Silvio's aqueduct, as we mentioned at the beginning of the article, is a channel that connects the third and fourth ventricle, in a system of four cavities or ventricles. The two lateral ventricles lie along the cerebral hemispheres and connect to the third ventricle through the interventricular or Monro foramen.

Regarding the third ventricle, it should be noted that it is a cavity located in the midline of the brain and is limited on each side by the thalamus and the hypothalamus. In its frontal part, it communicates, as we have commented, with the lateral ventricles and, in the posterior part, with the Silvio aqueduct.

For his part, the fourth ventricle is the one located at the lowest level of the four cerebral ventricles. It extends from the aqueduct of Silvio to the central canal of the upper end of the medulla. spinal cord, with which it communicates through several orifices: Luschka's foramina, located in the sides; and Magendie's foramen, located in the center and between the two Luschka's foramen.

• You may be interested in: "Cerebral Ventricles: Anatomy, Characteristics, and Functions"

Characteristics and development

The Silvio aqueduct, as its name indicates, is a channel or system of cerebrospinal fluid supply that connects the third and fourth ventricle, and that, together with the lateral ventricles, constitute the ventricular system that protects the brain, among other functions.

The development of the ventricular system occurs in parallel to the rest of the central nervous system. The cerebral ventricles are derived from the embryonic neuroepithelium. Both the ventricles, as well as the aqueduct of Silvio and the central canal of the spinal cord are lined by an epithelial layer of cuboidal and cylindrical cells, called ependymal cells.

From the fifth week of embryonic development, the encephalic vesicles differentiate into: telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. These vesicles are hollow inside and maintain their cavities until their development is complete. in adulthood: what we know as cerebral ventricles.

In the sixth week, the division of the encephalic vesicles is clearer; the forebrain has already been differentiated into the telencephalon and diencephalon. The midbrain, for its part, has not divided and its largest cavity narrows in the early stages of progressively, while the Silvio aqueduct is formed, which connects the third with the fourth ventricle.

The midbrain or mesencephalon is the structure that undergoes the least changes during development, except for its most caudal part. Finally, the length reached by the Silvio aqueduct is approximately 18 millimeters.

Related disorders

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 it occurs more frequently due to congenital than acquired causes. In cases in which congenital hydrocephalus occurs, teratogenic factors, malnutrition, toxins, etc. may influence.

There are three main types of hydrocephalus: communicating or non-obstructive, which originate when CSF absorption is not adequate; non-communicating or obstructive, which occur when the CSF flow is blocked in one or more channels that connect some ventricles with others; and normotensive, in which an increase in CSF is generated in the ventricles, with a slight increase in intracranial pressure.

One of the most common disorders related to damage to or obstruction of the Silvio aqueduct is known as hydrocephalus due to congenital aqueductal 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 of prenatal onset, producing signs of intracranial hypertension, thumb abduction, symptoms of spasticity, and severe intellectual deficit.

In children, one of the most typical symptoms involves a rapid increase in the circumference or size of the head. Other autonomic or somatic symptoms may also occur and may include vomiting, irritability, dreams, and seizures.

Although the consequences of hydrocephalus vary from patient to patient based on age, the progression of the disease and individual differences tolerance of the CSF, it should be noted that hydrocephalus due to stenosis of the aqueduct of Silvio represents the more severe end of the spectrum and has a poor prognosis. flattering.

Bibliographic references:

• Carlson, B. m. (2005). Human embryology and developmental biology. Elsevier,.
• López, L.P., Pérez, S. M., & de la Torre, M. m. (2008). Neuroanatomy. Pan American Medical Ed.