CSF Physiology, Pressure & Dynamics
Bulk flow
Bulk flow is the net, directional movement of cerebrospinal fluid from where it is produced to where it is absorbed.
In short: Bulk flow
- It is the overall, directional movement of CSF.
- It carries fluid from the ventricles toward the absorption sites.
- It is distinct from the pulsatile back-and-forth motion.
- Obstruction of bulk flow causes obstructive hydrocephalus.
What it is
Bulk flow is the net, one-directional movement of CSF from its sites of production (the ventricles) toward its sites of absorption (the subarachnoid space and venous system). It is the overall circulation, as opposed to the to-and-fro pulsations.
Understanding Bulk flow
CSF exhibits both a net bulk flow (carrying fluid along its pathway to be absorbed) and a pulsatile back-and-forth motion (driven by the heartbeat and breathing). The bulk flow is what moves CSF from production to absorption; when it is obstructed at any point in the ventricular pathway, fluid backs up and obstructive hydrocephalus develops. Understanding bulk flow clarifies how net CSF movement can be blocked even though local pulsations continue.
Why it matters
Understanding bulk flow helps families see how the net movement of CSF can be obstructed, causing fluid to accumulate, which is the basis of obstructive hydrocephalus.
Common questions
What is bulk flow?
The net, directional movement of CSF from production to absorption.
How is it different from pulsatile motion?
Bulk flow is the overall circulation; pulsatile motion is the back-and-forth movement.
What happens if bulk flow is obstructed?
Obstructive hydrocephalus develops.
Bottom line
Bulk flow is the net movement of CSF from production to absorption; its obstruction causes obstructive hydrocephalus.
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