Twice Negative PCR in a Patient With Herpes Simplex Virus Type 1 (HSV-1) Encephalitis.

Area of Science:

• Neurology
• Infectious Diseases
• Diagnostic Medicine

Background:

• Herpes simplex virus type 1 (HSV-1) encephalitis is a severe neurological condition with high mortality.
• Polymerase chain reaction (PCR) testing of cerebrospinal fluid (CSF) is the gold standard for diagnosing HSV-1 encephalitis due to its high sensitivity and specificity.

Observation:

• A case of autopsy-confirmed HSV-1 encephalitis is presented where initial CSF PCR tests were negative.
• The patient presented with fever, neurological deficits, and imaging findings suggestive of encephalitis.
• Despite initial negative PCR results, empiric antiviral treatment was initiated due to strong clinical suspicion.

Findings:

• A third CSF sample, taken later in the disease course, eventually tested positive for HSV-1.
• The patient's condition deteriorated, leading to withdrawal of care and subsequent autopsy confirmation of widespread HSV-1 meningoencephalitis.
• This case highlights the potential for false-negative PCR results in diagnosing HSV-1 encephalitis.

Implications:

• Negative CSF PCR results in suspected HSV-1 encephalitis should be interpreted with caution.
• Guidelines recommend repeat CSF PCR testing within 3-7 days and continued empiric therapy in suspicious cases.
• Early empiric acyclovir treatment is crucial for suspected HSV-1 encephalitis, even with inconclusive initial diagnostic tests.