Question

Which of the following is NOT TRUE about CSF?

• A. Removal of CSF during dural tap causes intense intracranial headache
• B. Normally contains no neutrophils
• C. Formed by arachnoid villi within the ventricles
• D. pH is less than that of plasma

Hint:

Choroid plexus makes CSF; arachnoid villi only absorb it.

Answer 1

The Correct Option is C

Step 1: The question asks for the false statement. Cerebrospinal fluid is formed mainly by the choroid plexuses inside the ventricles, with a smaller amount produced around blood vessels and along the ventricular walls. Arachnoid villi (granulations) do NOT form CSF; they absorb CSF back into the venous sinuses. So option (c) is the false statement and the answer.

Step 2: Option (a) is true. Removing CSF during a lumbar or dural tap lowers the buffering fluid cushion, the brain sags, and traction on pain-sensitive structures causes a low-pressure (post-tap) headache.

Step 3: Option (b) is true. Normal CSF contains lymphocytes and a few monocytes but no neutrophils; the appearance of neutrophils suggests bacterial infection.

Step 4: Option (d) is true. CSF pH is about 7.31 to 7.34, slightly lower than plasma pH of 7.35 to 7.45, because of its higher carbon dioxide and lower bicarbonate. Since only option (c) is incorrect, it is selected.