Deep within the brain there is a system of four irregularly shaped cavities called the cerebral chambers, ventricles or cerebral cavities. Each cerebral hemisphere has a lateral ventricle.



Fourth ventricle in red

Thirth ventricle in red

Lateral ventricles in red

Corridors of cavities and canals


The brain chambers are connected to each other through channels and openings. These cavities produce and contain a clear, watery fluid called cerebrospinal fluid or CSF.

In terms of composition, the fluid resembles blood plasma, but it contains more hydrogen ions (H+). 


Other names for this fluid:

  • Cerebrospinal fluid
  • Liquor
  • Spinal fluid (the fluid below the brainstem)


This cerebrospinal fluid circulates and this flow ultimately ends up in the spaces around the brain, meninges and spinal cord where it is absorbed into the bloodstream at the surface of the brain at the subarachnoid space.


Cerebrospinal fluid production

In the ventricles (both side ventricles, third and fourth ventricles) there is a network of capillaries called the choroid plexus.

Here, 400 to 500 milliliters of cerebrospinal fluid is produced every day by specialized brain cells.

This fluid is replaced several times a day. This is necessary because the brain can only contain a total of 150 milliliters of cerebrospinal fluid. So there is a permanent production, transport and breakdown of cerebrospinal fluid and there is a natural balance between production and drainage. If this balance is disturbed, the pressure may be increased or decreased.


Function of cerebrospinal fluid

The cerebrospinal fluid serves as a cushion for the brain and spinal cord. The brain floats, as it were, in this fluid and the fluid absorbs the first blows in the event of a collision. The fluid also nourishes the nerve cells and removes waste products from the nerve cells and helps regulate the temperature.



In the development and growth of the brain ventricles, as with other parts of the nervous system, three phases can be distinguished.

  • The embryonic phase (from fertilization to the eighth week),
  • The fetal phase (from the ninth week to birth),
  • The neonatal phase (first four weeks after birth).


Increased cerebral pressure due to too much cerebrospinal fluid

The consequence of illness or damage may be that cerebrospinal fluid production increases, disrupting the balance of supply, transport and breakdown.
When the cerebrospinal fluid cannot drain properly or is not or is barely absorbed into the bloodstream, the brain ventricles will become enlarged.
This is called ventriculomegaly.

This increase in cerebrospinal fluid results in increased cerebral pressure. The optic nerves are vulnerable to increased cerebral pressure. The increase in moisture creates a situation of hydrocephalus (hydro=water, cephalus=brain). Read more on our page on hydrocephalus.


Diseases and damage

There may be several causes for the increase in the production of cerebrospinal fluid or the disruption of the transport between the cavities or the drainage of the cerebrospinal fluid.


  • Disruption in the drainage of cerebrospinal fluid due to a
  • Disturbance in the drainage of the cerebrospinal fluid shortly after a sub-arachnoid hemorrhage (SAH). In that case the ventricles are filled with blood,
  • Intraventricular hemorrhage or intraventricular hematoma (IVH), the occurance of a bleeding in the ventricles, 
    • 1st degree; the hemorrhage occurs in a small area of the tricles,
    • 2nd degree; the bleeding also occurs in the ventricles,
    • 3rd degree; the ventricles expand and become larger due to the blood,
    • 4th degree; there are also hemorrhages in the brain tissues surrounding the ventricles.

Such an intraventricular hemorrhage is often a cerebral hemorrhage in the first days of life of a baby who was born prematurely, often with a low birth weight.

Intraventricular hemorrhage (IVH) in adults usually occurs with aneurysmal subarachnoid hemorrhage (SAH) or a cerebral hemorrhage caused by high blood pressure (hypertension-related intracerebral hemorrhage).
The greatest threat of IVH is the development of acute hydrocephalus/hydrocephalus with occlusion. If this result in neurological deterioration it must be treated urgently with a drain (external ventricular drainage /EVD) via an intraventricular catheter (IVC). A ventricular drain is also called a shunt.


  • Adhesion after a cerebral hemorrhage, after infections, an accident, or after tumors (benign and malignant),
  • Congenital defect,
  • Constriction of the connection between the third and fourth ventricle,
  • Disturbance in the development of the fourth ventricle
  • Brain tumor
  • Tumor in the production organ of cerebrospinal fluid (plexus papilloma)
  • Enlarged brain chambers/enlarged ventricles after traumatic brain injury/post traumatic ventriculomegaly. This is reported on average in one third of patients after traumatic head injury,
  • Normal Pressure Hydrocephalus due to old age, even resembles a dementia picture. Also called NPH; Normal Pressure Hydrocephalus. See the hydrocephalus page.




Idiopathic intracranial hypertension (IIH / IIIIH)

In idiopathic intracranial hypertension (IH/IIH) there is increased cerebral pressure. There is a high cerebrospinal fluid or
CSF pressure caused by a disturbance in the balance between production and drainage of cerebrospinal fluid. Idiopathic means that there is no explanation for the congestion of the cerebrospinal fluid. Intracranial means it is within the skull. 
Sometimes it is caused by medication, sometimes in excessive vitamin A use, in diseases such as Besnier Boeck, Lupus Erythematosus.

It is also possible that it is caused by other blood diseases, in which thrombosis may occur, an accumulation of inflammatory cells in the draining cavities (venous sinuses) or other causes of the chronic clogging of these cavities.


It may also be that too much cerebrospinal fluid is produced.
Obesity, especially in women between the ages of 20 and 44, has been associated with this condition. Possibly also through use of the contraceptive pill, which can increase the tendency of the blood to clot. This can cause the cavities to silt up. This rarely happens, see this study


The complaints may be similar to those that occur with a tumor in the head: headache, nausea, vomiting, blurred or less sharp vision, loss of visual field and double vision.


Characteristic is a narrowing of the field of view at the outer edge. With increased pressure in the head, the place where the optic nerve enters the eye (the entry point) has blurred edges (pupillary constriction). There is fluid accumulation (edema) in the optic nerve head. This is called papilledema or optic nerve swelling. The optic nerve may be permanently damaged by the increased pressure (papillary atrophy).


In practice it is difficult to distinguish between headaches from migraine and from idiopathic intracranial hypertension (IHH).
If there is no headache and no papilledema, the diagnosis of IIH cannot be made. Sometimes an MRI scan
necessary to be able to find the abnormalities if no papilledema was initially found.
Other complaints may include: pain in the neck, back, shoulders or arms, throbbing ringing in the ears (pulsating tinnitus), photosensitivity, nausea, cognitive complaints.


Synonyms for IIH

Sometimes the following outdated terms are still used to refer to Idiopathic Intracranial Hypertension:

  • Benign Intracranial Hypertension (BIH) = benign high pressure in the brain
  • Pseudotumor cerebri (PTC) = a pseudo brain tumor

It sometimes happens that the ventricles of the brain merge, which makes it difficult to install a drain to remove excess cerebrospinal fluid.


Increased brain pressure may also be due to the brain swelling after an accident. This is dangerous because the brain cells become compressed. The neurologist will make every effort to lower the pressure in the brain.
The patient is put asleep and pain relief is given. Medicines to lower the pressure are administered and a pressure monitor can be inserted through a thin tube by the neurosurgeon.

Research shows that patients with IIH have an increased risk of obstructive sleep apnea syndrome (OSAS).


Post-traumatic ventriculomegaly

After traumatic brain injury, on average, a third of patients develop a variant of hydrocephalus; post-traumatic ventriculomegaly, literally translated: enlarged ventricles.
This enlargement of the brain chambers was seen in 39.3% of cases after severe head injury. There was then no connection with age.
After moderate traumatic brain injury, it occurred in 27.3% of patients. It was clearly visible on a scan at 4 weeks post-injury in 57.6% of those affected and at two months in 69.7%. This problem is often overlooked.


Enlarged Alzheimer's Enlarged ventricles (ventriculomegaly) in Alzheimer's

Enlarged brain ventricles generally indicate brain atrophy = shrinkage of the brain, but this is also seen with normal aging.
In Alzheimer's disease, enlargement of the brain chambers also occurs because the brain tissue decreases. The cerebral cortex is shrinking.


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