Herpetic encephalitis: which treatment for which body weight?

Background Prognosis of herpetic encephalitis remains severe, with a high proportion of deaths and sequelae. Its treatment is based on acyclovir, but the precise and most effective modalities of this treatment are not established. The objective of this study was to determine them. Methods For this, we carried out a descriptive, retrospective, monocentric study, using the current coding database at Marseille University Hospitals. Cohort was intended to be exhaustive for the disease, from January 2000 to June 2019, including patients hospitalized in intensive care and conventional hospitalization sector. Patients ( n = 76) included were at least 16 years of age and had a clinical presentation, cerebral Magnetic Resonance Imaging, and/or electroencephalogram abnormalities consistent with herpetic encephalitis confirmed by a positive HSV-PCR in the CSF. Clinical data and treatment, including the doses actually administered to the patient, were compared according to patient’s outcome. Results The mortality rate was 12%, whereas 49% had complete recovery and 39% sequelae impeding independence. Poor outcome was statistically associated with persistence of confusion, aphasia, and impaired consciousness lasting more than 5 days, superinfection, status epilepticus, and length of stay in intensive care unit. A statistical decision tree, constructed using the Classification And Regression Tree model, to prioritize treatment management, showed two main factors that influence the outcome: the patient’s weight, and the average daily acyclovir dose actually administered. Conclusion These results suggest to modify acyclovir management in herpetic encephalitis, for low-weight patients (< 79 kg) with a minimum dosage of 2550 mg/day (850 mg/ 8 h), when possible.