Acyclovir-resistant herpes zoster encephalitis successfully treated with vidarabine: a case report

A 78-year-old man developed herpes zoster virus (HZV) encephalitis. Initially, treatment with aciclovir (750 mg per day) improved CSF cell count and protein level. During the treatment, however, encephalitis in the patient deteriorated in spite of the treatment with aciclovir, suggesting that HZV in the patient had become resistant to aciclovir. Subsequent treatment with vidarabine (600 mg per day, for 15 days) resulted in dramatic improvement in CSF pleocytosis. About two months after the discontinuation of vidarabine, the CSF cell count was normal. The patient became alert gradually, but his amnestic syndrome remained unchanged. Vidarabine may be recommended in the treatment of HZV encephalitis when aciclovir is not effective.