A non-randomized retrospective study of 45 adult patients (12 young adults) with herpes simplex virus encephalitis (HSVE), treated with acyclovir alone (23 patients) and acyclovir plus corticosteroids (22 patients), was conducted at Nihon University School of Medicine, Tokyo, Japan. At 3 months, a poor outcome was found in older patients, those with lower Glasgow Coma Scores at initiation of therapy, and in those not receiving corticosteroids in the acute stage. 
COMMENT. This study suggests that a combination of acyclovir with corticosteroids initiated at the acute stage of HSVE is a predictor of a better prognosis than acyclovir alone. The beneficial effects of corticosteroids may be explained by reduction of brain edema and regulation of the host immune response, decreasing the extent of viral infection.
Openshaw H and Cantin EM, in an editorial commentary , opine that the effectiveness of corticosteroids in HSVE can only be determined by prospective, randomized studies. The benefits observed in the above retrospective study could be related to selection of cases and to the corticosteroid therapy per se.
Concerns that early corticosteroid administration may increase viral CNS spread, leading to a restriction of steroids to cases with significant brain edema, may not be justified, based on recent animal studies cited by Kamei et al. [3, 4]. Early diagnosis is a factor in prognosis, and a characteristic EEG multifocal periodic pattern may be helpful when CT and ultrasound are normal in neonatal HSVE.