A 30-year-old woman presents with fever, headache and behavioural change progressing over 4 days. MRI shows temporal lobe involvement. CSF reveals lymphocytic pleocytosis with elevated protein and normal glucose. Which test on CSF confirms the most likely etiology?
- A CSF culture for bacteria
- B CSF PCR for herpes simplex virus type 1 DNA ✓
- C Serum IgM antibody titre against Japanese encephalitis virus
- D CSF India ink preparation
Correct answer: B. CSF PCR for herpes simplex virus type 1 DNA
Explanation
Temporal lobe localisation with a subacute lymphocytic CSF picture is classic for HSV-1 encephalitis, and CSF PCR for HSV DNA is the diagnostic standard with high sensitivity and specificity. Serum JE IgM cannot distinguish current CNS infection from exposure, India ink addresses cryptococcus which produces a different syndrome, and bacterial culture is irrelevant given the chronic-type CSF profile.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.