CSF, Ventricles & Brain Anatomy
Lateral ventricle
A lateral ventricle is one of the two largest fluid-filled cavities in the brain, one in each cerebral hemisphere.
In short: Lateral ventricle
- They are the largest of the four ventricles.
- They contain choroid plexus that produces CSF.
- Their enlargement is often the first sign of hydrocephalus on imaging.
- They connect to the third ventricle through the foramina of Monro.
What it is
A lateral ventricle is one of the two largest ventricles, with one located in each half (hemisphere) of the brain. Each is a C-shaped cavity containing choroid plexus and CSF.
Understanding Lateral ventricle
The lateral ventricles produce a large portion of the brain's CSF through their choroid plexus, and the fluid drains from each into the third ventricle through a channel called the foramen of Monro. Because they are the largest ventricles, their enlargement is often the most visible sign of hydrocephalus on imaging, and they are commonly measured to assess the degree of ventricular enlargement (for example, using the Evans index). Each lateral ventricle has regions named for the brain lobes they reach — frontal, occipital, and temporal horns, plus a body and an atrium.
Why it matters
Understanding the lateral ventricles helps families interpret imaging that measures ventricle size, since their enlargement is a key indicator used to assess and monitor hydrocephalus.
Common questions
How many lateral ventricles are there?
Two — one in each hemisphere.
Are they the largest ventricles?
Yes.
Why are they measured?
Their enlargement helps assess and monitor hydrocephalus.
Bottom line
The lateral ventricles are the two largest brain cavities, and their enlargement is a key sign of hydrocephalus.
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