CSF examination in a 25-year-old man with low-grade fever, neck stiffness, and cranial nerve palsies shows 80 cells/μL predominantly lymphocytes, protein 250 mg/dL, glucose 30 mg/dL with simultaneous blood glucose of 110 mg/dL, and a fine cobweb-like clot on standing. Adenase deaminase level in CSF is elevated. Which additional finding best supports the diagnosis of tuberculous meningitis?

• A Polymorphonuclear predominance with very low CSF chloride
• B Opening pressure below 10 cm of water
• C Positive CBNAAT (Xpert MTB/RIF) on the CSF sample ✓
• D Marked xanthochromia with normal protein

Explanation

Tuberculous meningitis classically gives lymphocytic pleocytosis, markedly raised protein, low CSF glucose relative to blood, and a cobweb coagulum formed by fibrin, with raised CSF ADA. CBNAAT on CSF provides rapid confirmation of M. tuberculosis DNA and rifampicin resistance status and is the recommended initial molecular test. Polymorphonuclear predominance suggests pyogenic meningitis, opening pressure is usually elevated rather than low, and normal protein contradicts the typical picture.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.