A case of acyclovir-resistant herpes simplex encephalitis improved dramatically by vidarabine (Ara-A)

A 56-year-old woman was admitted to our hospital with symptoms of fever and headache. On admission, she was drowsy and neurological examination showed remarkable nuchal stiffness and mild muscle rigidity of limbs. Cerebro-spinal fluid (CSF) showed moderate pleocytosis (824/3/mm³, N 59% and L41%). The brain CT demonstrated low density area in the left temporal lobe. The MRI showed high signal intensity area in the same site. CSF IgG antibody titer to herpes simplex virus type I showed more than 4 times as those on admission and we diagnosed her as herpes simplex encephalitis. Administration of intravenous acyclovir 1500 mg per day for 14 days seemed to be ineffective. Ara-A was tried 750 mg per day for 10 days and her symptoms and signs improved dramatically. About ten days after discontinuation of ara-A, she was relapsed but improved by readministration of ara-A again. She has had no relaspe or no sequelae until now. It is important that ara-A should be used for acyclovir resistant cases still and that termination of these antiviral drugs must be judged carefully because several relapsed cases are reported like our case.