Encephalitis in Infectious Mononucleosis: Diagnostic Considerations

Abstract

Four atypical cases of presumed infectious mononucleosis (IM) encephalitis are presented. To establish an etiologic diagnosis, Paul-Bunnell-Davidsohn heterophile titers (PBD), antibody titers to the antigens of the Epstein-Barr virus (EBV) and oropharyngeal excretion of EBV were determined. Criteria for a primary EBV infection are an antiviral capsid antigen titer of .gtoreq. 1:60, the presence of antibody to the diffuse component of the early antigen, absence of antibody to the nuclear antigen and excretion of the virus from the oropharynx. Of the 4 cases, met these criteria; of the three, 1 did not have a positive heterophile titer. The 4th case was IM; there was a positive PBD heterophil, but there was no evidence of primary EBV infection. Although the PBD heterophile is usually a reliable test to diagnosis IM, it is not always present in children, and it is sometimes nonspecifically elevated. Some EBV titers can be nonspecifically elevated. The above criteria are diagnostic of primary EBV infection.