Normal CSF composition differs from plasma. Which of the following accurately describes normal lumbar CSF values?

• A Protein 100–200 mg/dL, glucose 80–90% of plasma glucose, no cells
• B Protein 5–10 mg/dL, glucose equal to plasma glucose, 10–15 neutrophils/μL
• C Protein 45–100 mg/dL, glucose 40% of plasma glucose, 0–2 RBCs/μL
• D Protein 15–45 mg/dL, glucose 60–70% of plasma glucose, 0–5 lymphocytes/μL ✓

Explanation

Normal lumbar CSF: protein 15–45 mg/dL (much lower than plasma ~7 g/dL because the blood-brain barrier restricts protein entry); glucose 60–70% of simultaneous plasma glucose (active transport is not fully efficient); white cells 0–5 lymphocytes/μL (no neutrophils normally); pressure 70–180 mmH2O; pH ~7.33 (slightly lower than plasma). Elevated protein with xanthochromia suggests subarachnoid haemorrhage; low glucose with neutrophilia suggests bacterial meningitis.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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