A 25-year-old woman presents with fever, headache, and altered mental status over 2 weeks. She has a history of pulmonary tuberculosis. CSF analysis shows: protein 200 mg/dL, glucose 25 mg/dL (simultaneous blood glucose 110 mg/dL), and lymphocytic pleocytosis with 500 cells/μL. MRI shows basal meningeal enhancement. What is the most specific finding on CSF examination?
- A Positive AFB stain or Mycobacterium tuberculosis PCR ✓
- B High protein
- C Lymphocytic pleocytosis
- D Low glucose
Correct answer: A. Positive AFB stain or Mycobacterium tuberculosis PCR
Explanation
This describes tuberculous meningitis, which classically shows basal meningeal enhancement on imaging. While low glucose, high protein, and lymphocytic pleocytosis are characteristic, they are not specific. The most specific diagnostic finding is identification of Mycobacterium tuberculosis by AFB stain, culture, or PCR (CBNAAT/GeneXpert). In Indian exams, tuberculous meningitis is high-yield, and the basal meningeal pattern distinguishes it from pyococcal meningitis.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.