The clinical features of herpes simplex encephalitis (acute necrotizing encephalitis)

Abstract

The clinical picture of herpes simplex encephalitis is like that of all encephalitides, expectedly very variable. On the other hand, there are some important clinical indicators which if present make the diagnosis extremely probable and thus lead to brain biopsy and the concurrent administration of antiviral agents. These basic indicators may be listed as follows: (1) Clinical. Variable clouding of consciousness, personality change, bizarre behaviour, speech disorder and epileptic features of one sort or another (an essential negative factor is that there should be no potential source of pyogenic infection to suggest the alternative diagnosis of brain abscess). (2) Cerebro-spinal fluid. Lymphocytic pleocytosis. (3) Electroencephalogram. Diffuse slow-wave activity with or without localization, associated periodic 'irritation' waves, particularly from the second to fiftieth day of the encephalitic illness. (4) Angiography. An appearance of a spaceoccupying lesion, particularly of the temporal lobes, with no tumour vascular pattern. Paradoxically if angiography is normal in the presence of all the other features, then the herpetic diagnosis becomes even more probable.