Herpes Simplex Encephalitis in Adults and Older Children

Herpes simplex encephalitis (HSE) is a neurologically devastating illness associated with substantial morbidity and mortality in adults and older children. The correct recognition of HSE, and distinguishing it from other forms of encephalitis, brain abscess or mimicking disorders early in the course of evaluation facilitates treatment decisions when neurologic complications occur. The combination of clinical characteristics, magnetic resonance imaging of the head, and polymerase chain reaction (PCR) analysis of cerebrospinal fluid for herpes simplex type 1 DNA is a sensitive and specific way of diagnosing HSE for proper treatment. Early treatment is essential. HSE is treated with acyclovir 10 mg/kg every 8 hours intravenously for 21 days, unless the illness is mild, or if nephrotoxicity occurs. Whether prolonged therapy with oral antiviral treatment after standard intravenous acyclovir offers any advantage from the standpoint of neurologic morbidity or mortality is unproven. PCR-negative typical cases and PCR-positive atypical cases of HSE can occur and require treatment with acyclovir.