[Infection in the central nervous system and corticosteroid therapy]

No standardized therapy has been established for viral encephalitis except for herpes simplex encephalitis. Not a few neurologists, however, have had an impression that administration of corticosteroids ameliorated neurological impairment and induced better prognosis in some patients with viral encephalitis. Five patients with aseptic meningitis and 9 patients with viral encephalitis, who were moderately to severely ill, were examined for cerebrospinal fluid (CSF) parameters before and after short-term intravenous administration of corticosteroids. In all of the patients with aseptic meningitis, severe headache and nausea disappeared rapidly with this treatment, which was accomplished via anti-inflammatory effects of corticosteroids. By contrast, 5 of the patients with viral encephalitis responded well to intravenous corticosteroids, whereas the remaining 4 patients did not, three of whom showed poor prognosis. The CSF containing more than 15% of CD4+CD26+ memory helper T cells guaranteed good response to corticosteroid therapy. It appeared that viral encephalitis with severe inflammation had poor prognosis irrespective of attempted therapy including intravenous corticosteroids. The CSF of patients who responded well to corticosteroid treatment showed a significant reduction in CD4+CD29+ helper-inducer T cells in the course of the illness. This finding indicates that autoimmune mechanisms may be involved in the pathogenesis of neurological impairment in a part of patients with viral encephalitis.