CEREBRAL VENTRICLES: ANATOMY, FUNCTIONS AND DISEASES - GEOGRAFÍA - 2025

The cerebral ventricles are a series of interconnected cavities within the brain. These cavities are filled with cerebrospinal fluid and their main function is to protect the brain.

The set of cerebral ventricles is called the ventricular system and is located in the brain parenchyma. This is the functional tissue of the brain that controls cognition; the rest of the brain tissue is the one that serves as support.

The cerebral ventricles are divided into two lateral ventricles, the third ventricle and the fourth ventricle. These are connected to each other by small holes.

Inside the ventricles are the choroid plexuses that produce the cerebrospinal fluid, which surrounds the brain, spinal cord and fills the ventricular system. This liquid follows a constant cycle of production and reabsorption, nourishing the brain structures.

The cerebral ventricles have about 1/5 of the volume of adult cerebrospinal fluid, that is, between 20 and 25 milliliters.

Anatomy

The ventricular system. Source: OpenStax CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)

Lateral ventricles

They are the largest cavities of the ventricular system and there is one inside each hemisphere, dividing into the right ventricle and the left ventricle.

The lateral ventricles are C-shaped. Each of them is divided into a central part, made up of the body and the trigone or atrium, and three lateral extensions or "horns."

Size and location of the ventricular system in the human head. Source: BodyParts3D by DBCLS. CC BY 2.1 Japan (https://creativecommons.org/licenses/by/2.1)

The central part is located in the parietal lobe. While the roof is made up of the corpus callosum. In the inferolateral area we find the dorsal thalamus and the tail of the caudate nucleus, and on the floor is the anterior part of the fornix, the choroid plexus, the dorsolateral surface of the thalamus, the terminal stria and part of the caudate nucleus.

The lateral ventricles connect to the third ventricle through two interventricular foramina, also called foramina of Monro. These holes are located between the thalamus and the anterior part of the fornix.

The lateral ventricles have horns that project into the occipital, frontal, and temporal lobes. The volume of these ventricles increases with age.

Third ventricle

The third ventricle consists of a narrow groove found in the diencephalon of the brain, between the right and left thalamus. It connects with the fourth ventricle through the cerebral aqueduct or also called Silvio's aqueduct, which descends through the midbrain.

Its anterior surface has two protrusions:

- The supraoptic recess: located on the optic chiasm.

- The infundibular recess: which is located above the optic stalk.

Fourth ventricle

This ventricle is the lowest ventricle in the ventricular system. It is found in the brain stem, in the area where the bridge of Varolio and the brainstem meet. Its floor is made up of a part of the rhombencephalon, called the rhomboid fossa.

The fourth ventricle is located below the midbrain, posterior to the pons, in front of the cerebellum, and above the medulla oblongata. It communicates with two different channels:

- Central spinal canal, which allows cerebrospinal fluid to reach the spinal cord.

- Subarachnoid cisterns, which allows cerebrospinal fluid to reach the cerebral meninges to a place called the subarachnoid space. The subarachnoid space covers the entire brain allowing this fluid to surround the entire structure.

In the subarachnoid cisterns, the cerebrospinal fluid is reabsorbed.

The fourth ventricle communicates with the subarachnoid space through the lateral foramen of Luschka and through the median foramen of Magendie, which is located in the roof of the ventricle.

Functions of the cerebral ventricles

Ventricular system of the human being. Source: BodyParts3D by DBCLS. CC BY 2.1 Japan (https://creativecommons.org/licenses/by/2.1)

The ventricles of the brain are filled with cerebrospinal fluid. This fluid is largely formed in the choroid plexuses, which are very small vascular structures, which filter blood plasma to create it. It performs important functions in our central nervous system, which is why there are so many spaces in the brain that contain it.

In addition, the cerebrospinal fluid gives the brain buoyancy, this helps to reduce its weight. Thus, the pressure at the base of the brain that would exist if it were not surrounded by the liquid is reduced.

The buoyancy allows to reduce the weight from about 1400 grams to about 50 grams. The main functions of the cerebral ventricles are:

- Allow the cerebrospinal fluid to circulate through the structures of the central nervous system, with them it is possible to maintain an adequate internal homeostasis, allowing the circulation of important substances to regulate the functions of our body.

It also allows us to defend ourselves from external agents that can be dangerous for the brain, that is, it provides immunological protection. Likewise, it keeps the nervous structures nourished, eliminating their waste.

- Maintains adequate intracranial pressure. Thanks to the cranial ventricles, changes in blood volume within the brain can be compensated so that intracranial pressure does not increase or decrease.

- Acts as a shock absorber to be filled with fluid, thus preventing brain damage due to blows or other injuries to the skull.

In short, the cerebral ventricles serve for the cerebrospinal fluid to reach the most internal structures of our brain, increasing its protection against trauma and keeping the tissues nourished, free of waste and threatening substances.

Development of the cerebral ventricles

The four ventricles of the brain develop to the embryonic stage during the first trimester of pregnancy. They arise from the central canal of the neural tube.

At the end of the first month of gestation, approximately, the three cerebral vesicles are formed. These are the forebrain, midbrain, and rhombencephalon.

The neural tube dilates within the forebrain, so that the space within that tube widens, forming the lateral ventricles and the third ventricle.

The midbrain cavity gives rise to the cerebral aqueduct, while the fourth ventricle is formed with the dilation of the neural tube in the rhomboencephalon.

Diseases related to the cerebral ventricles

Several diseases can affect the brain ventricles. The most common are: hydrocephalus, meningitis and ventriculitis.

It is very important that the production of cerebrospinal fluid is balanced with its reabsorption so that it does not accumulate more than necessary. Many of the pathologies that affect the cerebral ventricles are due to an obstruction of these.

Also its enlargement or decrease can be a sign of different pathologies. The most common abnormalities of the ventricular system are described below:

Hydrocephalus

Hydrocephalus is the accumulation of cerebrospinal fluid in the brain ventricles by not absorbing it as it should. If left untreated, it causes elevated intracranial pressure and brain atrophy.

Very dilated ventricles are seen on brain scans. There are two types of hydrocephalus according to their causes:

- Communicating hydrocephalus: occurs when fluid accumulates without obstructions in the circulation. It is usually due to deterioration of the arachnoid granulations that reabsorb cerebrospinal fluid.

- Non-communicating or obstructive hydrocephalus: it is due to an obstruction within the ventricular system. They are usually found in the cerebral aqueduct, the one that joins the third and fourth ventricles.

The symptoms of hydrocephalus are: headaches, drowsiness, loss of coordination, blurred vision, seizures, nausea, as well as cognitive changes such as problems maintaining attention or psychomotor retardation.

If this process occurs before the fontanelles have fused, that is, before the different regions of the skull join, macrocephaly can be observed. In this, the size of the skull grows abnormally.

Whereas, if the fontanelles have fused, it is more likely to compress and damage the adjacent tissues.

Brain atrophy

The ventricles have also been observed to expand in neurodegenerative diseases, in parallel with brain atrophy. This is what happens, for example, in Alzheimer's disease.

Meningitis

Meningitis is a disease in which the meninges of the brain and spinal cord, that is, the layers that cover it and that contain the cerebrospinal fluid, become inflamed. It is usually caused by viruses, fungi or bacteria, producing an increase in intracranial pressure and difficulties for the circulation of cerebrospinal fluid.

It is accompanied by headache, cognitive impairment, nausea, sensitivity to light, sudden fever, muscle weakness, etc.

Ventriculitis

Ventriculitis, as its name suggests, is the inflammation of the cerebral ventricles, which encompasses all four chambers.

Ventriculitis is a serious complication of any meningitis. It is linked to the absence of antibiotic treatment. It is accompanied by hydrocephalus and is associated with arachnoiditis, encephalitis, cerebritis, and encephalomyelitis.

Schizophrenia

Some scientists have found links between schizophrenia and the extension of the brain ventricles. Specifically, it appears that schizophrenics have larger ventricles than healthy people.

However, it is not clear whether it is mental disorders that lead to enlargement of the ventricles or whether it is ventricular dilation that is responsible for mental disorders.

On the other hand, obstructions in the ventricular system can also occur due to tumors, cysts, trauma, abnormalities in development, vascular malformations (aneurysms), etc.

On the other hand, it is common to observe an asymmetry in the lateral ventricles in brain scans. In an article in which the asymmetry of the ventricles of the human fetal brain was studied, it was found that this was a normal variant that did not involve any pathology.

According to Orellana (2003), what helps to determine that asymmetry is an anatomical variant and not a pathology, is that, normally, in the variant, the temporal horns are the same size and even, sometimes, the contralateral is more dilated.

References

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