Encephalitis in infectious mononucleosis.

Three cases of infectious mononucleosis encephalitis are presented in which the aetiological diagnosis was established by specific Epstein-Barr virus serology. Paul-Bunnell-Davidsohn tests were negative in all cases, and characteristic nonneurological features of infectious mononucleosis were present in only one. The 3 cases had blood serological tests diagnostic of a recent infection with Epstein-Barr virus. The Epstein-Barr virus is one of the more common causes of sporadic encephalitis particularly in young patients and the diagnosis may be considered even in the absence of systemic features of mononucleosis. As there is a substantial false negative rate with the Paul-Bunnell test, confirmation of recent infection may be gained by specific viral serology.