Atypical herpes simplex encephalitis: clinical, virologic, and neuropathologic evaluation.

An atypical form of herpes simplex encephalitis produced by HSV-1 documented in the present article demonstrates that (1) prominent EEG abnormality may correlate with subtle increase in signal intensity on MRI; (2) the disease may start with prominent involvement of the cingulate gyri; and (3) viral infection of the brainstem may cause early onset of severe neurologic dysfunction and coma.