Non-herpes simplex encephalitis is early exclusion of herpes simplex etiology possible?

Since effective antiviral treatment is available for herpes simplex encephalitis (HSE), early diagnosis or exclusion of herpes simplex etiology is essential for prognosis. In a retrospective study of 25 cases of acute viral encephalitis not caused by herpes simplex virus (non-HSE), we investigated whether HSE can be excluded in the early phase before serological evidence is present. Using clinical means, history, investigations of CSF (protein, cells), EEG, and CCT, HSE could not be excluded with reliability. This is because clinical signs and laboratory results are not pathognomonic for any form of viral encephalitis, even if periodic activity in EEG and temporal attenuation in CCT are more frequent in HSE than in other forms of encephalitis. Therefore, in all cases of severe encephalitis, acyclovir therapy should be initiated early.