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Viral infections of the central nervous system (CNS) may be variously categorized by type of onset (eg, acute, subacute, chronic, or recurrent), by the level of the CNS involved (eg, brain, brain stem, or spinal cord), and by the viral agent causing disease. The approach to diagnosis and management of CNS viral infection depends greatly on the age, immunization history, and immune status of the patient, and also the epidemiologic setting including season, location, and exposure to viruses that are circulating in the community or transmitted by arthropod vectors. Molecular testing techniques continue to evolve to improve identification of viral agents causing CNS diseases.
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ACUTE VIRAL MENINGITIS
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Community-acquired viruses and arthropod-borne viruses are the major causes of the acute “aseptic meningitis” syndrome that, by definition, is accompanied by symptoms and signs of meningeal inflammation in the absence of acute bacterial or fungal meningitis. Although meningitis may occur in the course of infection with many viruses (Table 227-1), the human enteroviruses (EVs) have been shown to be responsible for the majority of cases of viral meningitis, most prominently the nonpolio EVs. Other well-known causes of viral meningitis include herpesviruses (herpes simplex virus [HSV], Epstein-Barr virus [EBV], cytomegalovirus [CMV], human herpesvirus [HHV]-6, and varicella-zoster virus [VZV]), mumps virus, lymphocytic choriomeningitis virus (LCMV), influenza virus, and the arthropod-borne viruses (including West Nile virus [WNV], St. Louis encephalitis virus, La Crosse [LAC] virus, and eastern equine encephalitis virus).
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Because EVs cause more than 90% of cases, even during periods of peak arbovirus transmission, the epidemiology of viral meningitis usually reflects the trends of EV infection in the population, including seasonal peaks in late summer and fall and a strong inverse correlation between age and observed rates of disease. Overall rates of EV infection are several-fold higher for infants under 12 months of age than older children. The observed rates of meningitis ...