[Value of gene amplification of herpesviruses in the diagnosis and treatment of acute viral encephalitis]. / Valeur de l'amplification génique du virus herpétique dans le diagnostic et le traitement des encéphalites aiguës virales.

Positive diagnosis of Herpes simplex virus (HSV) encephalitis was rarely obtained in the past, when brain biopsy had been performed. Other tests (HSV antigen and HSV antibodies detection and interferon alpha measurement, in cerebrospinal fluid) failed to prove HSV infection. Polymerase chain reaction has been proposed for accurate and rapid diagnosis of HSV encephalitis. With 35 cycles of a DNA polymerase sequence duplication, sensitivity reaches 95% and specificity 100%. HSV PCR is a useful tool for the diagnosis of acute encephalitis. This should be available in many neurologic clinics. Therapeutic consequences include rapid disruption of aciclovir when clinical features, MRI study and negative PCR suggest non herpetic encephalitis.

Significance and clinical relevance of the detection of herpes simplex virus DNA by the polymerase chain reaction in cerebrospinal fluid from patients with presumed encephalitis.

The polymerase chain reaction (PCR) was used to detect DNA of herpes simplex virus (HSV) in 38 samples of cerebrospinal fluid (CSF) obtained from 22 patients (7 children and 15 adults) 1-20 days after the onset of encephalitis. The results were best with amplification on the pellet of the CSF-extracted DNA and with analysis of the amplified products by dot-blotting (sensitivity, 100%). A highly significant difference was evident in the chi 2 test when PCR was compared with specific antigen detection or antibody evaluation (n = 19; chi 2 = 7; sensitivity = 100% vs. 63%) or with interferon alpha determination (n = 20; chi 2 = 11; sensitivity = 95% vs. 42%). PCR was positive as early as 1 day after onset of disease and was often the first test to become positive. The detection of HSV DNA by PCR is the most specific, rapid, and sensitive tool for early diagnosis and therapeutic management of acute HSV encephalitis.