Predictors of a Prolonged Clinical Course in Adult Patients with Herpes Simplex Virus Encephalitis

Objective Herpes simplex virus encephalitis (HSVE) patients occasionally follow a prolonged course despite standard antiviral treatment. The purpose of this study was to analyze clinical variables to identify predictors of a prolonged course. Methods A series of 23 HSVE patients treated with acyclovir (ACV) during the acute stage were selected and divided into 2 groups: the non-prolonged group (n = 15), with improvement within 2 weeks after initial ACV treatment; and the prolonged group (n = 8), without improvement within 2 weeks. Differences in clinical variables, including age, duration from onset to initial ACV treatment, Glasgow coma scale (GCS) score, corticosteroid administration, detection of abnormal lesions on initial cranial computed tomography (CT) and magnetic resonance imaging, detection of periodic lateralized epileptiform discharges on electroencephalogram, and clinical outcome, were compared between the groups. Results There were significant differences in GCS score, clinical outcome, and detection of lesions on CT between the non-prolonged and prolonged groups [p = 0.021, p = 0.041 (Mann-Whitney's U test), respectively, and p = 0.027 (Fisher's exact test)]. Four of the eight patients with a prolonged course had a poor outcome despite treatment with additional drugs. Conclusion A lower GCS and a higher rate of lesions on CT were identified as predictors of a prolonged course for HSVE. These predictors are in accordance with the conventional predictors of poor outcome for HSVE. This study suggests that the initial ACV treatment was insufficient for HSVE patients with these predictors at the acute stage. The initial treatment may need to be modified for such patients.