CSF, Ventricles & Brain Anatomy
Fourth ventricle
The fourth ventricle is the cavity near the brainstem and cerebellum that connects the ventricular system to the spaces around the brain and spinal cord.
In short: Fourth ventricle
- It sits between the brainstem and the cerebellum.
- It connects to the spaces around the brain through three outlets.
- Blockage of its outlets can cause hydrocephalus.
- It is the last ventricle in the CSF pathway.
What it is
The fourth ventricle is the lowest ventricle, located between the brainstem (in front) and the cerebellum (behind). It is the final cavity of the ventricular system before CSF exits into the spaces around the brain.
Understanding Fourth ventricle
CSF flows into the fourth ventricle from the third ventricle through the cerebral aqueduct, and exits through three outlets — the two foramina of Luschka (on the sides) and the foramen of Magendie (in the middle) — into the subarachnoid space. Blockage of the aqueduct above or of these outlets can cause hydrocephalus. Conditions affecting the back of the brain, such as Dandy-Walker malformation or posterior fossa tumors, can involve the fourth ventricle and disrupt CSF flow.
Why it matters
Understanding the fourth ventricle helps families see how CSF leaves the ventricular system and why blockages at this level — or in the structures around it — can cause hydrocephalus.
Common questions
Where is the fourth ventricle?
Between the brainstem and the cerebellum.
How does CSF leave it?
Through the foramina of Luschka and Magendie.
Can problems here cause hydrocephalus?
Yes — blockage of its outlets or nearby structures can.
Bottom line
The fourth ventricle is the last ventricle, connecting the system to the spaces around the brain through three outlets.
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