A description of the aqueduct of Silvio (or the midbrain), its location and its characteristics.
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, between other relevant functions for our body.
In this article we explain what the Silvio aqueduct is, what its characteristics are, where it is located, what functions it performs, how it develops and what are the main disorders associated with a malfunction of this brain structure.
What is the Silvio aqueduct?
In neuroanatomy, it is known as the aqueduct of Silvio, cerebral aqueduct or aqueduct of the midbrain to the conduit located in the midbrain that is responsible for connecting the third and fourth ventricles of the brain, and through which the cerebrospinal fluid (CSF) that permeates the brain and spinal cord.
CSF is a liquid substance that fulfills basic functions in our nervous system, among which the following stand out: 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 of Silvio aqueduct is in disuse and in the current anatomical nomenclature the name that this brain structure receives is the midbrain aqueduct or, simply, cerebral aqueduct. However, throughout this article we will use the term Silvio aqueduct to refer to it.
Location and structure
Silvio’s aqueduct is located within the midbrain or midbrain , one of the parts that make up the brain stem. This brain structure is located on the pons or bridge of Varolio and below the diencephalon (made up 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 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 have commented at the beginning of the article, is a channel that communicates the third and fourth ventricles, in a system of four cavities or ventricles. The two lateral ventricles are located 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 back part, with the Silvio aqueduct.
For its part, the fourth ventricle is the one that is located at a lower level of the four cerebral ventricles. It extends from the aqueduct of Silvio to the central canal of the upper end of the spinal cord, with which it communicates through several orifices: the Luschka foramina, located on the sides; and the Magendie hole, located in the center and between the two Luschka holes.
Features and development
The Silvio aqueduct, as its name suggests, is a canal or cerebrospinal fluid irrigation system that connects the third and fourth ventricles, and which, together with the lateral ventricles, constitute the ventricular system that protects the brain, among others 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, the aqueduct of Silvio and the central canal of the spinal cord are lined by an epithelial layer of cuboidal and columnar cells, called ependymal cells.
From the fifth week of embryonic development, the encephalic vesicles are differentiated into: telencephalon, diencephalon, midbrain, metancephalon, and myelncephalon. These vesicles are hollow inside and maintain their cavities until their development is complete in adulthood: what we know as cerebral ventricles.
By the sixth week, the division of the encephalic vesicles is clearer; the forebrain has already differentiated into the telencephalon and diencephalon. The midbrain, for its part, has not been divided and its largest cavity gradually narrows in the early stages, while Silvio’s aqueduct is formed, which communicates the third with the fourth ventricle.
The midbrain or midbrain is the structure that undergoes the least changes during development, except for its most caudal part. Finally, the length of the Silvio aqueduct is approximately 18 millimeters.
Hydrocephalus are 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 causes than acquired. In cases where 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 occurs when CSF flow is blocked in one or more of the channels that connect some ventricles to 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 the damage or obstruction of the aqueduct of Silvio is known as hydrocephalus due to congenital aqueduct stenosis (HSAS). This disease, associated with a phenotype that is part of the clinical spectrum of the L1 syndrome linked to the X chromosome, causes severe obstructive hydrocephalus, usually of prenatal onset, which produces signs of intracranial hypertension, abduction of the thumb, symptoms of spasticity and a serious deficit intellectual.
In children, one of the most typical symptoms involves a rapid increase in head circumference or size. Other autonomic or somatic symptoms may also occur which may include vomiting, irritability, dreams, and seizures.
Although the consequences of hydrocephalus vary from one patient to another depending on age, disease progression and individual differences in CSF tolerance, it should be noted that hydrocephalus due to stenosis of the aqueduct of Silvio represents the most serious extreme of the disease. spectrum and has a bleak prognosis.
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