CSF Physiology, Pressure & Dynamics
CSF absorption (reabsorption)
CSF absorption is the return of cerebrospinal fluid to the bloodstream, mainly through the arachnoid granulations.
In short: CSF absorption (reabsorption)
- It balances the continuous production of CSF.
- It occurs mainly through arachnoid granulations into the venous blood.
- Impaired absorption is a common cause of communicating hydrocephalus.
- Other absorption pathways, including lymphatic routes, are recognized.
What it is
CSF absorption (or reabsorption) is the process by which cerebrospinal fluid is returned from the spaces around the brain into the bloodstream. It balances the ongoing production of CSF to keep the total volume and pressure stable.
Understanding CSF absorption (reabsorption)
Most CSF is absorbed through the arachnoid granulations, which project into the brain's venous channels (such as the superior sagittal sinus), allowing fluid to pass from the subarachnoid space into the venous blood. When absorption is impaired — for example, by scarring or clogging after bleeding or infection — CSF accumulates, causing communicating hydrocephalus. Increasingly, additional absorption pathways, including lymphatic and perivascular (glymphatic) routes, are recognized as contributing to CSF clearance.
Why it matters
Understanding CSF absorption helps families see why impaired absorption — a frequent consequence of hemorrhage or infection — leads to the communicating type of hydrocephalus, where fluid builds up despite flowing out of the ventricles normally.
Common questions
Where is CSF absorbed?
Mainly through arachnoid granulations into the venous blood.
Why does absorption matter?
It balances production; impaired absorption causes fluid buildup.
What impairs it?
Often bleeding or infection that scars the absorption sites.
Bottom line
CSF absorption returns fluid to the bloodstream, mainly via arachnoid granulations; impaired absorption causes communicating hydrocephalus.
Browse all 265 Hydrocephalus definitions
Read the Hydrocephalus patient guides
Not sure which page you need? Put words to it with the symptom navigator