Electron microscopic observations on the virus particles in Herpes simplex encephalitis.

Cerebral cortex from eight fatal cases of Herpes simplex encephalitis has been studied by electron microscopy. The diagnosis had been based on clinical findings, necropsy evidence of bitemporal necrosis, and histological confirmation of intranuclear inclusions with a lymphocytic inflammatory response, even though virus cultures were unsuccessful. Virus particles were seen predominantly in nuclei in six of these cases, utilizing tissue which had been preserved in formalin for up to four years or had been embedded in paraffin. Although demonstration of these particles is only indicative of the herpes group and not specifically of Herpes simplex, electron microscopy of either biopsy or postmortem material may be a useful adjunct in making the diagnosis and can be accomplished before virological studies have been completed.