Which statement correctly describes CSF production and circulation?

• A. CSF is produced at about 500 ml per day and is reabsorbed to maintain a circulating volume of about 150 mL
• B. CSF is produced at 5 liters per day
• C. CSF does not circulate around the spinal cord
• D. CSF is formed by neurons of the brain

Answer: (A)

CSF production and turnover are governed by continuous secretion and reabsorption that keep a small, steady circulating volume. In adults, the choroid plexus makes about 500 mL of CSF each day, while the total CSF volume in the ventricular and subarachnoid spaces is around 150 mL. This means CSF is constantly renewed as it flows through the system and is reabsorbed, so the circulating volume stays roughly at that 150 mL.

CSF flows through a defined pathway: from the lateral ventricles through the foramina of Monro into the third ventricle, down the aqueduct of Sylvius to the fourth ventricle, and then into the subarachnoid space around the brain and spinal cord. It is mainly reabsorbed into the venous system via arachnoid villi and granulations, helping to maintain pressure and volume.

The statement is correct because CSF is produced by the choroid plexus, not by neurons, and the daily production rate and the typical adult circulating volume align with established physiology. The other ideas—producing CSF at 5 liters per day, no circulation around the spinal cord, or CSF being formed by neurons—don’t fit known CSF physiology.