Approximately how much CSF is present at any given time?

Approximately how much CSF is present at any given time?

• A. 50 mL
• B. 250 mL
• C. 450 mL
• D. 150 mL

Answer: (D)

CSF volume is kept in balance by continuous production and reabsorption. In adults, the total CSF present at any given time is about 150 mL. The choroid plexus makes CSF at roughly 0.3–0.4 mL per minute (around 500 mL per day), and it’s reabsorbed through arachnoid granulations into the venous system. This turnover means the system maintains roughly 150 mL of CSF circulating in the ventricles and subarachnoid spaces. Values like 50 mL or 450 mL don’t fit this steady-state balance, and 250 mL is still higher than the typical total.

CSF volume is kept in balance by continuous production and reabsorption. In adults, the total CSF present at any given time is about 150 mL. The choroid plexus makes CSF at roughly 0.3–0.4 mL per minute (around 500 mL per day), and it’s reabsorbed through arachnoid granulations into the venous system. This turnover means the system maintains roughly 150 mL of CSF circulating in the ventricles and subarachnoid spaces. Values like 50 mL or 450 mL don’t fit this steady-state balance, and 250 mL is still higher than the typical total.