Long-term outcome of severe herpes simplex encephalitis: a population-based observational study

Abstract

AbstractIntroduction: Herpes simplex encephalitis (HSE) is a rare disease with a poor prognosis. No recent evaluation ofhospital incidence, acute mortality and morbidity is available. In particular, decompressive craniectomy has rarely beenproposed in cases of life-threatening HSE with temporal herniation, in the absence of evidence. This study aimed toassess the hospital incidence and mortality of HSE, and to evaluate the characteristics, management, the potentialvalue of decompressive craniectomy and the outcome of patients with HSE admitted to intensive care units (ICUs).Methods: Epidemiological study: we used the hospital medical and administrative discharge database to identify hospitalstays, deaths and ICU admissions relating to HSE in 39 hospitals, from 2010 to 2013. Retrospective monocentric cohort: allpatients with HSE admitted to the ICU of the university hospital during the study were included. The use of decompressivecraniectomy and long-term outcome were analyzed. The initial brain images were analyzed blind to outcome.Results: The hospital incidence of HSE was 1.2/100,000 inhabitants per year, 32 % of the patients were admitted toICUs and 17 % were mechanically ventilated. Hospital mortality was 5.5 % overall, but was as high as 11.9 % in ICUs. Inthe monocentric cohort, 87 % of the patients were still alive after one year but half of them had moderate to severedisability. Three patients had a high intracranial pressure (ICP) with brain herniation and eventually underwentdecompressive hemicraniectomy. The one-year outcome of these patients did not seem to be different from that ofthe other patients. It was not possible to predict brain herniation reliably from the initial brain images.Conclusions: HSE appears to be more frequent than historically reported. The high incidence we observed probablyreflects improvements in diagnostic performance (routine use of PCR). Mortality during the acute phase and long-termdisability appear to be stable. High ICP and brain herniation are rare, but must be monitored carefully, as initial brainimaging is not useful for identifying high-risk patients. Decompressive craniectomy may be a useful salvage procedurein cases of intractable high ICP