Autopsy neuropathological findings in 'burnt out' herpes simplex encephalitis and use of the polymerase chain reaction to detect viral DNA.

We have conducted an autopsy study of the brains of three patients with 'burnt out' temporal and frontal lobe encephalitis, thought to be due to previous herpes simplex virus infection. The brains showed marked atrophy and yellow-brown discolouration predominantly involving the anterior part of both temporal lobes. Histology revealed destruction of grey and white matter, perivascular and leptomeningeal aggregates of lymphocytes and macrophages, and severe gliosis. Immunohistochemistry for herpesvirus antigens was negative but, by use of the polymerase chain reaction, a segment of the thymidine kinase gene of herpes simplex virus type 1 was detected in sections of temporal lobe from all three brains. These findings support the hypothesis that herpes simplex virus may persist within the central nervous system after acute herpes encephalitis, to cause latent or low-grade productive infection.