Background: Herpes simplex virus encephalitis (HSE) may relapse following recovery from an acute episode,
but virus persistence within the central nervous system can’t always be demonstrated in clinical
practice during relapses, with a relevant impact on therapeutic management.
Case Report: In December 2002 a 41-years old woman was admitted due to high fever and convulsions;
electroencephalogram (EEG), cerebral nuclear magnetic resonance (NMR) findings and herpes simplex virus polymerase chain reaction (HSV-PCR) on cerebrospinal fluid (CSF) led to a diagnosis of HSE. The patient received a 21 days course of i.v. acyclovir and was discharged with mild cognitive abnormalities.
After one month the woman turned up again and presented worsening of memory impairment and behavioural abnormalities: t2-weighted images showed extension of hyperintense lesions in the right temporal lobe and reappearance of oedema in the fronto-parietal regions bilaterally. HSV-1 PCR on CSF tapping yielded a negative result. Based on clinical findings and NMR images, antiviral treatment was restarted and continued for three months (two weeks of i.v. acyclovir and ten weeks with valacyclovir per os) obtaining clinical improvement and the resolution of oedema on NMR.
Conclusions: Relapsing herpes virus encephalitis is a rare occurrence mainly reported in paediatric patients. Our case shows that this event may be observed even in adults and underlines the need of
close clinical follow-up. Post infection prophylaxis or maintenance therapy need further investigations.

Keywords: Encephalitis, herpes simplex virus, acyclovir, valacyclovir