By Dr. Ravindra Patil
A ventricle is a hollow part or cavity in an organ. The word ventricle originates from Latin, the language which has given most of the words used in anatomy and medicine. Ventricles of brain are cavities within the brain. Ventricles of the brain have distinctive functions, which we will see in this article.
Two major organs of the major organs of the human body which have ventricles are the heart and the brain. The ventricles of the heart pump blood through our body, while the ventricles of the brain are cavities within the brain that produce and store a liquid called cerebrospinal fluid (CSF). This liquid surrounds our brain and spinal cord, cushions them and protects them from injury. The CSF is also responsible for removing waste and delivering nutrients to our brain.
There are four ventricles in the brain. They are interconnected cavities. They extend throughout the brain. As has been mentioned, they produce, store and circulate the cerebrospinal fluid (CSF).
The two lateral ventricles of brain are C-shaped chambers found in the cerebral hemispheres, which is one in each hemisphere.
Lateral ventricles are connected to the third ventricle by an opening called the inter-ventricular foramen. The third ventricle is a very narrow cavity that runs along the midline of the diencephalon.
What structure connects the third and fourth ventricles? The third ventricle communicates with the fourth ventricle via the cerebral aqueduct. The fourth ventricle is wedged between the cerebellum on one side and the brainstem on the other; it extends to the central canal of the spinal cord. Which means in effect, the four ventricles extend from the brain to the end of the spinal cord. The CSF surrounds the brain and is also within the ventricles. The CSF is a liquid cushion in which the brain literally floats. The brain ventricles essentially supply, store and circulate the CSF around the brain.
The CSF is a thick viscous fluid which serves to cushion the brain, regulate its temperature and supply the brain with nutrients.
When looking at the interior of the brain, the four hollow ventricular cavities stand out in contrast to the rest of the organ, which is mostly composed of brain tissue, which in turn is made of grey matter and white matter. The main ventricle function is of course, producing CSF.
As the ventricles contained nothing except fluid, in ancient times it was thought that the ventricles contained ‘animal spirits’, a mysterious substance that allowed the immortal soul to exert control over the physical body. Later it was thought that the ventricles were credited with functions like the generation of imagination and memory. However, it was in 1764 that it was discovered that the ventricles were filled with CSF, fluid, and not animal spirits. And the CSF flowed around and inside the brain through the connections between ventricles. The ventricles gave the CSF a route to flow throughout the brain. Gradually it was discovered that it is the production, storage and circulation of CSF which is the main role of the ventricles.
The production of CSF is done by a specialized membrane called the choroid plexus, which is made up of ependymal cells. This choroid plexus lines the ventricles in brain. Ependymal cells are glial cells tailored to produce CSF, and they secrete the fluid into the ventricles at a relatively constant rate; about a half a litre of CSF is produced by ependymal cells every day. CSF passes through the ventricular system and circulates around the brain and spinal cord in a small area between the meninges called the subarachnoid space.
CSF is thought to play many important roles in the brain. The CSF and the brain ventricular system together keep the brain buoyant, reducing its weight and hence the physical stress it would otherwise experience from the forces of gravity and movement. The brain is a very delicate and soft organ. If the brain would not have been suspended in the CSF, it would have been distorted with its own weight! While organs like the kidney and liver and heart are much sturdier, the brain is very soft. Without being suspended in a fluid the delicate tissue of the brain can tear.
There is about 125–150 mL of CSF at any one time. The actual mass of the human brain is about 1400–1500 grams; however, the net weight of the brain suspended in CSF is equivalent to a mass of 25-50 grams. The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight. Had the brain been suspended in the skull without floating in the CSF, its blood supply would have been cut off and its neurons would be killed in the lower sections of the brain!
The layer of CSF surrounding the brain also acts as a buffer against potential injuries that can be caused by mechanical pressure or force (e.g. being hit hard in the head). Additionally, as the CSF circulates over the brain it carries away toxins and other waste matter and empties these into the bloodstream where they can eventually be removed by mechanisms like kidney filtration.
The rate of CSF production in the ventricles is fairly constant regardless of changes in pressure within the ventricles (i.e. inter-ventricular pressure). This can be problematic if the passage of CSF is blocked somewhere within the ventricular system. In the ventricular system of brain, CSF will continue to be produced, but it will have no means of exiting the system. This will cause pressure within the ventricles to increase, and the rising pressure may eventually force the ventricles to expand. The expanding ventricles can then put pressure upon other brain structures, and cause a variety of complications depending on where exactly the blockage has occurred and which structures are most affected by the blockage.
When such a blockage of the brain ventricles occurs in children whose skull has not completely become bony [generally under age of 2 years], it results in the enlargement of the head. It is known as hydrocephalus. Hydrocephalus can be cause by blockage in the passage of CSF as well as by excess CSF production. In lay language, hydrocephalus is referred as ‘Water in the Brain’.
There can be a number of causes of a blockage that leads to hydrocephalus, such as a tumour, infection, or congenital malformation, which impedes the function of ventricles. Hydrocephalus can often be treated by surgically implanting a shunt that drains the ventricles of excess CSF and empties it into the abdominal cavity. This approach can be successful, but if the reason for the blockage isn’t resolved additional surgeries may be required in the future (e.g. to replace an outgrown shunt, treat an infected shunt, etc…).
A contrast CT Scan can show the size and shape of the ventricles in brain. Either a radiopaque dye is injected in the patient’s veins or the CSF is replaced with air and then CT Scan of brain ventricles is done. In either case, a good contrast will be seen and the ventricles can be visualised. While the radio opaque dyes shows up as white colour, air shows up as black colour in CT scans and that helps doctors view the ventricular shape and size and reach a diagnosis about tumours, raised CSF pressure or blockage in the brain ventricular system.
Samarth Neuro and Superspeciality Hospital in Miraj has all the infrastructure and staff to treat hydrocephalus in children and other reasons of CSF blockage. The chief neurosurgeon Dr Ravindra Patil has operated upon many children suffering from hydrocephalus who needed shunts. These children are now grown up. Dr Ravindra Patil has also successfully operated on many adult patients with brain tumours.
Samarth Neuro and Superspeciality Hospital has 100+ beds & specializes in emergency surgery for neurological issues/disorders & diagnostics.
Samarth Neuro and Superspeciality Hospital
