How Cerebrospinal Fluid is Formed

Most cerebrospinal fluid is formed in the lateral ventricles of the cerebrum by the modified ependymal cells on the choroid plexus.

From the lateral ventricles, fluid moves through interventricular foramina into the third ventricle.

The choroid plexus of the third ventricle contributes fluid, which then passes through the aqueduct of sylvius into the fourth ventricle, where further additions to  the CSF are made in the roof of the Fourth Ventricle by the choroid plexus.

The fluid then enters the subarachnoid space the foramen of Magendie and the foramina of Luschka.

Some fluid passes downward into the spinal subarachnoid space, but the majority rises through the tentorial notch and finds its way slowly over the surface of the hemispheres to be absorbed mainly through the arachnoid villi and granulations into the venous system.

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