Question

A patient presented with a high fever, altered sensorium, headache, neck rigidity, and seizures. He was diagnosed with HSV encephalitis. Which of the following tests can be used to confirm the diagnosis?

• A. IgM in CSF
• B. Tzanck smear of CSF
• C. CSF PCR for viral DNA
• D. CSF culture on chick embryo lines

Answer 1

The Correct Option is C

To diagnose HSV encephalitis, we need a test that can detect the presence of the Herpes Simplex Virus directly in the cerebrospinal fluid (CSF). The options we have include:

• IgM in CSF
• Tzanck smear of CSF
• CSF PCR for viral DNA
• CSF culture on chick embryo lines

One of the most reliable and specific methods for confirming HSV encephalitis is the use of PCR (Polymerase Chain Reaction) to detect viral DNA in the CSF. This technique is noted for its high sensitivity and specificity in identifying the presence of HSV DNA, making it the diagnostic method of choice.

Let's evaluate the options:

• IgM in CSF: Detecting IgM antibodies in the CSF can suggest recent infection but is not definitive for HSV detection due to cross-reactivity and lower sensitivity.
• Tzanck smear of CSF: This is typically used for skin lesions associated with HSV, not for CSF analysis.
• CSF PCR for viral DNA: This is the correct test. PCR directly detects viral DNA, which provides a specific and rapid confirmation of HSV infection in the central nervous system.
• CSF culture on chick embryo lines: Viral culture methods are generally less sensitive and much slower compared to PCR.

Therefore, the recommended test to confirm HSV encephalitis diagnosis is CSF PCR for viral DNA.