Herpes simplex encephalitis

Abstract

Diagnostic and therapeutic advances in the management of herpes simplex encephalitis (HSE) have been significant over the last decade. Serological analysis of simultaneously drawn CSF and serum samples allows reliable diagnostics of HSE, but not until after 3-10 days following the onset of neurological symptoms. Polymerase chain reaction (PCR) assay with two nested primer pairs, being developed for the amplication of HSV DNA in CSF, was applied to 151 CSF samples from 43 consecutive patients with HSE. As controls, 87 CSF samples from 60 patients with acute febrile focal encephalopathy (initially suspected to be HSE but excluded by the absence of intrathecal HSV antibody synthesis) were tested. PCR detected HSV DNA in 42/43 patients and remained positive up to 27 days after the onset of neurological symptoms. By a combination of PCR and serological analysis of intrathecal HSV antibody synthesis, aetiological diagnosis of HSE can be made by one or both methods from early disease and up to 15 years after the onset of HSE. In one Swedish and one American trial of acyclovir versus vidarabine in HSE, acyclovir 10 mg/kg 8-hourly for 10 days significantly decreased mortality as well as morbidity in the survivors. Early start of acyclovir treatment is necessary in HSE; the prognosis is correlated to age and stage of consciousness and neurological involvement at start of the therapy. Data has shown the need of neuropsychological assessment in final determination of the level of disability after HSE. The profiles and dynamics of the inflammatory cascade of cytokines from lymphocytes and other brain cells, provoked by the intracerebral HSV infection, needs to be characterized to enable understanding of the pathogenic process in HSE and hence its adequate antiinflammatory treatment.