Lumbar Puncture for HSV Testing in Newborns
Yes, lumbar puncture with CSF HSV PCR testing is essential for diagnosing neonatal HSV infection, as it is the test of choice for detecting CNS involvement and guides treatment duration.
Diagnostic Approach
CSF HSV PCR is the gold standard test for diagnosing neonatal HSV encephalitis or disseminated disease with CNS involvement 1. The American Academy of Pediatrics recommends obtaining cultures from multiple sites including blood, skin vesicles, mouth/nasopharynx, eyes, urine, and stool/rectum, but CSF analysis via lumbar puncture is critical for detecting CNS disease 2.
Key Testing Considerations
- CSF HSV PCR has high sensitivity (74-90%) for detecting neonatal HSV infection when combined with serum testing 3
- Negative CSF does not exclude skin-limited HSV disease, as only 60% of neonates with skin lesions have CNS involvement 4
- False-negative PCR results can occur, especially early in disease course, so if HSE remains suspected (particularly with temporal lobe involvement on imaging), repeat LP should be performed within 3-7 days 1
Treatment Implications Based on LP Results
The LP result directly determines treatment duration:
- CNS or disseminated disease: IV acyclovir 20 mg/kg/dose three times daily for 21 days, with mandatory repeat CSF HSV DNA PCR at day 19-21 before discontinuing therapy 2
- Skin, eye, and mouth disease only: IV acyclovir 20 mg/kg/dose three times daily for 14 days 2
Critical Management Point
Do not discontinue therapy for CNS disease until repeat CSF HSV DNA PCR is negative at the end of treatment 2. Persistence of HSV DNA in CSF after 15-21 days of high-dose acyclovir is associated with severe developmental delay or death 5.
When to Perform LP
Lumbar puncture should be performed unless contraindications exist, including 6:
- Moderate to severe impairment of consciousness or fall in GCS >2
- Focal neurological signs or unequal/poorly responsive pupils
- Papilledema
- Systemic shock or clinical instability
- Coagulation abnormalities (platelet count <100 × 10⁹/L)
- Local infection at LP site
Clinical assessment, not CT imaging, should be the primary determinant of LP safety 6.
Common Pitfalls
- Vesicular rash is present in only 60% of neonates with CNS or disseminated HSV disease, so absence of skin lesions should not deter LP if HSV is suspected 4
- Traditional CSF findings (elevated WBC or RBC counts) do not reliably predict HSV and should not be the sole basis for testing decisions 7
- High-risk infants are frequently undertested: studies show 62% of high-risk infants do not undergo HSV testing and 75% do not receive acyclovir 8
- Empiric acyclovir should be started immediately while awaiting culture results given the catastrophic consequences of untreated neonatal HSV 4