[Herpes simplex encephalitis]

Herpes simplex encephalitis (HSE) is a severe disease with high mortality and morbidity. As effective antiviral therapy improves the outcome of younger patients, the early diagnosis of the disease has become important, especially in children. The annual incidence of HSE in Japan among children is estimated to be about 100-200 cases, and the mortality is 10-20%. Instead of brain biopsy, we applied the polymerase chain reaction (PCR) assay to the early diagnosis. The DNA of herpes simplex virus was detectable in CSF of all HSE patients in the acute phase. Serial quantitation of viral genome by PCR also revealed that the amount of DNA decreased gradually corresponding to antiviral therapy, and it turned to be negative 3 to 18 days after the onset of neurological signs and symptoms (mean 10.1 days). These results show the PCR assay is a useful diagnostic tool for the early and non-invasive diagnosis of HSE.