Aqueduct of Sylvius: characteristics of this cerebral canal.

A description of the aqueduct of Sylvius (or midbrain), its location and characteristics.

The aqueduct of Sylvius is a duct or canal 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 relevant functions for our organism.

In this article we explain what the aqueduct of Sylvius 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 malfunction of this brain structure.

What is the aqueduct of Sylvius?

In neuroanatomy, the aqueduct of Sylvius, cerebral aqueduct or midbrain aqueduct is known as the aqueduct of Sylvius, cerebral aqueduct or midbrain aqueduct. the midbrain that connects the third and fourth ventricles of the brain, and through which cerebrospinal fluid (CSF), which permeates the brain and spinal cord, passes. (CSF) that permeates the brain and spinal cord.

CSF is a liquid substance that fulfills basic functions in our nervous system, including: acting as a protector against cranioencephalic trauma; providing hydropneumatic support; eliminating residual metabolites from the nervous system; and acting as a homeostatic mechanism when certain hormonal imbalances occur in the organism.

Currently, the name aqueduct of Sylvius is no longer in use and the anatomical nomenclature in 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 aqueduct of Sylvius to refer to it.

Location and structure

The aqueduct of Sylvius is located within the 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 thalamus). (composed of the thalamus and hypothalamus, among other structures), and is composed of the tectum (or roof), located dorsally; and the tegmentum (or tegument), located just below the tectum.

The midbrain or mesencephalon is made up of several neural nucleiThe 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 nuclei whose functions are related to motor control, learning and reward mechanisms.

The aqueduct of Sylvius, as mentioned at the beginning of this article, is a channel that connects the third and fourth ventricles, in a system of four cavities or ventricles. The two lateral ventricles are located along the cerebral hemispheres and are connected to the third ventricle through the interventricular foramen or foramen of Monro.

The third ventricle is a cavity located in the midline of the brain and is bounded on each side by the thalamus and hypothalamus. In its frontal part it communicates, as mentioned above, with the lateral ventricles and, in the posterior part, with the aqueduct of Sylvius.

The fourth ventricle, on the other hand, the fourth ventricle is the one located at a lower level of the four cerebral ventricles.. It extends from the aqueduct of Sylvius to the central canal at the upper end of the spinal cord, with which it communicates through several orifices: the foramina of Luschka, located on the sides; and the foramen of Magendie, located in the center and between the two orifices of Luschka.

Characteristics and development

The aqueduct of Sylvius, as its name indicates, is a channel or a cerebrospinal fluid irrigation system that connects the third and fourth ventricles.The ventricular system, together with the lateral ventricles, constitutes 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. The ventricles, the aqueduct of Sylvius and the central canal of the spinal cord are lined by an epithelial layer of cubic 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 completed in adulthood. in adulthood: what we know as cerebral ventricles.

In the sixth week, the division of the encephalic vesicles is clearer; the forebrain has already differentiated into the telencephalon and diencephalon. The midbrain, on the other hand, has not divided and its larger cavity narrows progressively in the early stages, while the aqueduct of Sylvius, which connects the third and fourth ventricles, is formed.

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 aqueduct of Sylvius is approximately 18 millimeters.

Related disorders

Hydrocephalus is a group of diseases caused by an increase in cerebrospinal fluid (CSF) in the interior of the brain. (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 in which congenital hydrocephalus occurs, teratogenic factors, malnutrition, toxins, etc. may play a role.

There are three main types of hydrocephalus: communicating or non-obstructive, which arise when CSF absorption is inadequate; non-communicating or obstructive, which occur when CSF flow is blocked in one or more of the channels connecting one ventricle to another; and normotensive, in which there is an increase of CSF in the ventricles, with a slight increase in intracranial pressure.

One of the most common disorders related to damage or obstruction of the aqueduct of Sylvius is the so-called hydrocephalus due to congenital stenosis of the aqueduct (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, resulting in 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 head circumference or size. 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 depending on age, disease progression, and individual differences in CSF tolerance, it should be noted that hydrocephalus due to stenosis of the aqueduct of Sylvius represents the more severe end of the spectrum and has a poor prognosis.

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. Ed. Médica Panamericana.