Herpes simplex virus encephalitis. Diagnostic and treatment considerations

The patient with meningoencephalitis should be evaluated carefully for the presence of focal signs referable to involvement of the frontotemporal regions of the brain. A significant percentage of cases of encephalitis with discrete focal features are caused by infection with herpes simplex virus. If focal signs are not present, the patient should be managed conservatively but examined regularly because focal neurologic dysfunction may present at any time in the course of disease. If there is clinical and electrographic evidence of involvement of the frontotemporal lobes, radiographic imaging is indicated as well as studies of the serum and cerebrospinal fluid for antibodies indicative of a recent infection with herpes simplex virus. Assuming that the radiographic scans identify the characteristic changes of a focal encephalitis and that the antibody responses are indicative of a recent herpes simplex virus infection, brain biopsy should be done in order to confirm the diagnosis. With positive evidence for HSE, treatment with ara-A should be initiated and continued for 10 days. If the biopsy proves negative for virus, ara-A should be discontinued and the patient managed conservatively (Fig. 3). Although the NIAID study of ara-A treatment of HSE is encouraging, the numbers are small and the evidence is, at best, only suggestive. It is reasonable to use this drug until a better one becomes available for the treatment of known HSE, and treatment should be instituted early before cellular injury is extensive. In centers familiar with this problem, biopsy confirmation of the diagnosis is a simple and informative procedure and can be defended. If patients cannot be moved to a center of this type, physicians familiar with the many facets of this problem should be consulted, and a decision regarding biopsy and treatment should be individualized in light of the circumstances. Biopsy should only be undertaken when the procedure can be done with minimal risk to the patient and the assurance that the maximum amount of information can be gained.