CSF, Ventricles & Brain Anatomy
Third ventricle
The third ventricle is a narrow, central cavity that connects the two lateral ventricles to the fourth ventricle.
In short: Third ventricle
- It sits in the center of the brain, between deep structures.
- It connects to the lateral ventricles via the foramina of Monro.
- Its floor is the site of endoscopic third ventriculostomy (ETV).
- It drains to the fourth ventricle through the cerebral aqueduct.
What it is
The third ventricle is a thin, central cavity located in the middle of the brain, between important deep structures. It is part of the continuous CSF pathway.
Understanding Third ventricle
CSF flows into the third ventricle from both lateral ventricles through the foramina of Monro, and out of it to the fourth ventricle through the cerebral aqueduct. Its central location and thin walls make the floor of the third ventricle the target for endoscopic third ventriculostomy (ETV), in which a surgeon creates an opening in this floor to let CSF bypass a downstream blockage. The third ventricle is therefore central both to normal CSF flow and to a key treatment for obstructive hydrocephalus.
Why it matters
Understanding the third ventricle helps families see how CSF flows through the center of the brain and how an ETV works — by creating a new opening in its floor to bypass a blockage.
Common questions
Where is the third ventricle?
In the center of the brain.
What connects to it?
The lateral ventricles (via the foramina of Monro) and the fourth ventricle (via the aqueduct).
What procedure involves it?
ETV, performed through its floor.
Bottom line
The third ventricle is the central cavity connecting the lateral ventricles to the fourth, and the site of ETV.
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