Duration of vidarabine therapy in biopsy-negative herpes simplex encephalitis.

Vidarabine therapy reduces mortality due to herpes simplex encephalitis (HSE) from 70% to 40% at one year. Treatment with vidarabine is commonly terminated five days after biopsy in suspected HSE if herpes simplex virus is not isolated from the biopsy specimen. However, as demonstrated by this case report, virus distribution in brain tissue may be patchy, even within the temporal lobe. In addition, several technical factors in the process of virus isolation can result in falsely negative results at five days. To protect this subgroup of patients with HSE, a full ten-day course of antiviral therapy should be considered for patients with focal encephalitis whose biopsy results are negative, provided that HSE remains the principal diagnostic possibility. However, the potential benefit of vidarabine treatment must be weighed against the risk of side effects, particularly cerebral edema. For optimum care, patients with presumed HSE should be transferred to centers whose personnel have expertise in the diagnosis and management of this disease.