The brain’s ventricular system is a network of interconnected, fluid-filled cavities. Deep within the cerebral hemispheres lie the largest of these, a pair of structures known as the lateral ventricles. They are part of a larger system that includes the third and fourth ventricles, all connected by narrow channels. This entire system is lined with a specialized membrane and plays a role in maintaining the brain’s environment.
Anatomy of the Lateral Ventricles
There are two lateral ventricles, one in each cerebral hemisphere. Their complex shape is described as a “C” curve, mirroring the general form of the hemisphere they occupy. This structure means they extend across multiple lobes of the brain, including the frontal, parietal, and occipital lobes. Each lateral ventricle has an estimated capacity of 7–10 mL.
The C-shaped cavity is composed of five distinct parts:
- The anterior (or frontal) horn, which curves forward into the frontal lobe.
- The body, which is the main central section.
- The collateral trigone (or atrium), a triangular area that connects other parts.
- The posterior (occipital) horn, which projects into the occipital lobe.
- The inferior (temporal) horn, which curves down into the temporal lobe.
The boundaries of the lateral ventricles are formed by several adjacent brain structures. For instance, the roof is largely formed by a bundle of nerve fibers called the corpus callosum, which connects the two cerebral hemispheres. The floor and walls involve structures like the thalamus and the caudate nucleus.
Cerebrospinal Fluid Production and Flow
The ventricles are filled with cerebrospinal fluid (CSF), a clear liquid that performs several functions for the brain. CSF acts as a cushion, protecting the brain from mechanical shock, and it circulates nutrients and chemicals filtered from the blood. It also serves to remove waste products from the brain.
Most of this fluid is produced by a specialized tissue called the choroid plexus. This structure, which is composed of epithelial cells surrounding capillaries, is found within all the ventricles, including the lateral ventricles. The choroid plexus acts as a barrier, controlling which substances pass from the blood into the CSF, and it generates approximately 500 mL of new fluid each day.
The circulation of CSF follows a specific pathway through the ventricular system. After being produced in the lateral ventricles, CSF flows through two small openings called the interventricular foramina to enter the third ventricle. From there, it travels through a narrow channel known as the cerebral aqueduct into the fourth ventricle. Finally, the fluid exits the ventricular system into the subarachnoid space that surrounds the brain and spinal cord before being reabsorbed into the bloodstream.
Clinical Significance and Associated Conditions
Disruptions to the normal volume or flow of cerebrospinal fluid can lead to medical issues. A primary condition is hydrocephalus, which involves an excessive accumulation of CSF. This buildup causes the ventricles to expand and increases pressure inside the skull, which can damage brain tissue. Treatment for hydrocephalus involves surgically implanting a shunt to drain the excess fluid and relieve pressure.
A related term, ventriculomegaly, refers to the enlargement of the ventricles and is identified during prenatal ultrasound scans. While it can be a sign of hydrocephalus, it is a description of size and does not always indicate a pressure problem.
Changes in the size of the lateral ventricles can also indicate other neurological conditions. In neurodegenerative disorders like Alzheimer’s disease, the loss of brain tissue, or atrophy, can cause the ventricles to appear larger as a secondary effect. Similarly, altered ventricular size has been observed in studies of individuals with schizophrenia, suggesting a link to changes in brain structure associated with the condition.