Cerebrospinal fluid is produced at approximately 500 mL/day, yet the total CSF volume is only 150 mL. At what rate is CSF produced, and where is it primarily absorbed?

• A 1.5 mL/min; primarily absorbed by the ependymal cells lining the ventricular walls
• B 0.35 mL/min; primarily absorbed at the choroid plexus via active transport
• C 0.35 mL/min; primarily absorbed at the arachnoid villi (granulations) into the dural venous sinuses ✓
• D 0.1 mL/min; primarily absorbed at foramina of Magendie and Luschka into the subarachnoid space

Explanation

CSF is produced at ~0.35 mL/min (500 mL/day) by the choroid plexuses (primarily in the lateral ventricles). It flows from lateral ventricles → third ventricle → cerebral aqueduct → fourth ventricle → subarachnoid space via foramina of Magendie and Luschka. Absorption occurs primarily at arachnoid villi (granulations) into the dural venous sinuses, driven by the pressure gradient between CSF (8–15 cmH2O) and venous sinus pressure. Obstruction of absorption causes communicating hydrocephalus.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.