CSF examination in a 34-year-old man with 3 weeks of low-grade fever, evening headache, and cranial nerve palsies shows 80 cells/microlitre predominantly lymphocytes, protein 250 mg/dL, glucose 30 mg/dL (simultaneous blood glucose 110 mg/dL), and a cobweb-like coagulum on standing. What is the most likely diagnosis?

• A Pyogenic meningitis
• B Tuberculous meningitis ✓
• C Viral meningitis
• D Cryptococcal meningitis

Explanation

Lymphocytic pleocytosis with markedly raised protein, low CSF glucose relative to blood, a subacute course with basal cranial nerve palsies, and the characteristic cobweb coagulum point to tuberculous meningitis. Viral meningitis gives a normal CSF glucose, which excludes option C. Pyogenic meningitis shows neutrophilic pleocytosis with very low glucose. Cryptococcal meningitis can mimic the picture but typically occurs in immunocompromised hosts and lacks the cobweb clot, which reflects very high fibrin and protein content.

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

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Written and medically reviewed by the StethoPrep medical team.