Viral meningitis is part of the
aseptic meningitis syndrome but must be distinguished from
bacterial meningitis on the basis of a careful examination of the CSF and sound clinical judgment. Enteroviruses probably account for the bulk of cases of
aseptic meningitis that occur in the United States and which are reported to the Centers for Disease Control each year. The seasonal pattern in the incidence of
aseptic meningitis is largely due to the seasonal variation of enteroviral
infections. Early on, the CSF in patients with
viral meningitis frequently contains a predominance of polymorphonuclear leukocytes and may even have a low
glucose level. The presence of neutrophils in the initial CSF sample is especially common in patients with enteroviral
infections. A CSF
glucose level lower than 50 per cent of a simultaneously drawn
blood glucose determination is not uncommon in patients with
viral meningitis due to
mumps, LCM, and
herpes simplex. In a patient with a predominance of polymorphonuclear leukocytes in the initial CSF specimen and in whom a
viral infection is suspected,
antibiotics may be withheld if a spinal tap is repeated within 12 hours. A shift from polymorphonuclear leukocytes to mononuclear cells makes
viral meningitis the likely diagnosis. Both
herpes simplex and
varicella-
zoster may infect the meninges by means of spread from cervical and dorsal root ganglia in a retrograde fashion much the way they spread in an antegrade fashion to the skin. HSV-2 is more likely to cause the clinical syndrome of
viral meningitis, while HSV-1 is more likely to cause a
meningoencephalitis with serious brain dysfunction. The identification of a specific viral agent in body fluids, especially the CSF, in a patient with
aseptic meningitis is of more than academic interest, since it can shorten duration of
hospital stay and eliminate unnecessary antimicrobial
therapy. The diagnosis of enteroviral
infections depends upon the isolation of a virus from CSF, stool, or throat plus a fourfold antibody response in the serum to the viral isolate. The 60-odd serotypes of enterovirus, each with different
antigenic determinants, preclude serologic testing alone as a useful diagnostic test to identify the patient infected with coxsackievirus or echovirus. For
infections, due to
herpes simplex,
varicella-
zoster, LCM, and arboviruses, a serologic test alone can be useful.(ABSTRACT TRUNCATED AT 400 WORDS)