Re-examination of Encephalitic Brains Known to Contain Intranuclear Inclusion Bodies: Electron-microscopic Observations Following Prolonged Fixation in Formalin

Abstract

Brain tissue known to contain intranuclear inclusion bodies from eight fatal cases of encephalitis was studied by light and electron microscopy. This study demonstrated that prolonged fixation of autopsy specimens in formalin provided sufficient preservation to allow electron microscopic identification of viral particles. Differentiation between subacute sclerosing panencephalitis (SSPE) and herpes encephalitis was easily established in each of the eight cases studied. Two cases had such short encephalitic courses that SSPE was not considered until observations were made by electron microscopy. Light microscopic recognition of inclusion bodies in these two diseases may be difficult because most of them occur in small nuclei and characteristically they lack halos. Inclusion bodies with halos were seen only in cells with large nuclei, such as neurons. The discrepancy found in the literature regarding light microscopic identification of inclusion bodies is ascribed to failure to recognize inclusion bodies without halos. Some differences between the light microscopic characteristics of inclusion bodies in the two diseases were observed.