A 3-week-old presents with perioral vesicles, seizures, and CSF pleocytosis with elevated protein. Brain MRI shows hemorrhagic temporal lobe involvement. The mother had no visible genital lesions at delivery. Which investigation would confirm the diagnosis most rapidly?
- A Tzanck smear from vesicles
- B Maternal serology for HSV-2 IgG
- C CSF HSV PCR ✓
- D Skin biopsy for viral culture
Correct answer: C. CSF HSV PCR
Explanation
Neonatal herpes simplex encephalitis is confirmed by HSV PCR on CSF, which is the most sensitive and specific rapid test. Temporal lobe hemorrhagic encephalitis with seizures in a neonate is classic for HSV-2 CNS disease. Tzanck smear has low sensitivity and only identifies multinucleate giant cells without typing. Maternal serology reflects prior exposure and does not confirm neonatal infection. IV acyclovir should be started empirically while awaiting PCR results.
Reference: Ghai Essential Pediatrics, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.