What Is the ventricular system of the brain?

The brain produces fluid called cerebral spinal fluid (CSF). If the flow of the CSF is blocked by traumatic brain swelling or blood from trauma, excessive amounts of CSF can be trapped. With the increased fluid, the ventricular system enlarges causing pressure on adjacent brain structures. This may cause damage to the brain and even death. The condition of excess CSF in the brain is known as hydrocephalus. (A large section of this website is devoted to explaining some of the variations of hydrocephalus. See (Understanding Hydrocephalus).

The ventricular system is spread diffusely throughout the brain.

Cerebral Spinal Fluid (CSF) is mostly made in the ventricular system of the brain. This fluid then circulates throughout the brain as well as down the spine. This is the same fluid obtained with a spinal tap (lumbar puncture). Notice how the fluid filled structure (the ventricular system drawn in purple) occupies space in all the lobes of the brain.

Anatomy (Nomenclature) of the Ventricular System

ventricular system parts labeled

The ventricular system sections are mostly named by which lobe of the brain they occupy. Therefore, the occipital horn is located in the occipital lobe. The temporal horn is in the temporal lobe. The body of the ventricle crosses the parietal lobe. The frontal horn is in the frontal lobe. The III (3rd) ventricle is at the level of the thalamus or top of the brainstem. The IV (4th) ventricle is in the posterior fossa under the cerebellum at the posterior aspect of the brainstem at the level of the pons. The aqueduct (of Sylvius) connects the III ventricle with the IV ventricle. Sometimes people will refer to the right or left lateral ventricle. This usually refers to the frontal horn, body, occipital and temporal horns on that particular side of the brain. The CSF (Cerebral Spinal Fluid) will flow from the lateral ventricle down through the foramen of Monro into the III ventricle. From there it proceeds down the aqueduct into the IV ventricle. There are three openings in the IV ventricle: two openings laterally (to the sides) are the foramen of Lushka and medially or in the middle is the foramen of Magendie.

This video shows how the csf flows within the ventricular system. When it reaches the bottom of the ventricular system (IVth ventricle) it circulates down into the spinal cord and out into the brain. When there is too much fluid in the ventricular system, the ventricles dilate and squeeze the surrounding brain tissue. This is hydrocephalus.

Ventricular System and CAT Scan or MRI Scan Radiographic Correlation

One can correlate the labeled anatomical parts of the ventricle above with the radiologic studies to better understand how to read the CT or MRI scan which is often obtained after head trauma. In the third image, the white is blood in the frontal horn of the ventricle blocking the foramen of Monroe. This is causing build up of excess fluid (early hydrocephalus).

body of the lateral ventricles CT with Frontal Horn and IIIrd Ventricle labeled hemorrhage in the frontal horn going into the IIIrd Ventricle via the Foramen of Monro IVth ventricle labeled

Bleeding Into The Brain Causing Early Obstructive Hydrocephalus

CT of Basal Ganglia Hemorrhage With Hydrocephalus

The ventricular system can be obstructed anywhere along its path.(See Hydrocephalus: Obstructive Type.) The CT Scan shows an enlarged ventricular system. CSF (Cerebral Spinal Fluid) cannot flow past the blood clot so the lateral ventricles are enlarged.

Bleeding Into The Brain Causing Early Obstructive Hydrocephalus

Brain Model Showing Blood In The Frontal Horn, Occipital Horn, Basal Ganglia With Hydrocephalus

The CSF flow is beginning to become obstructed by the hemorrhage. Obstuctive hydrocephalus is developing.