Relapse of herpes simplex encephalitis after acyclovir therapy.

Acyclovir is a new and well tolerated anti-viral agent whose role in the treatment of herpes simplex encephalitis (HSE) is still being evaluated. Although relapse of adenosine arabinoside treated HSE has been documented, this paper describes the recurrence of encephalitis after treatment with the recommended course of Acyclovir. A more extended course of Acyclovir produced a rapid and sustained improvement with minimal residual neurological deficit. We emphasise the need for more prolonged treatment and an awareness of the possibility of relapse when using Acyclovir for HSE.