Which laboratory finding is typically seen in meningitis caused by viral infections?

In cases of meningitis caused by viral infections, a lymphocytic predominance in the white blood cell (WBC) count is a hallmark laboratory finding. This shift indicates an increased production of lymphocytes, which are a type of white blood cell involved in the immune response against viral pathogens. Viral meningitis typically does not show the same degree of inflammatory response as bacterial meningitis, which often results in a predominance of neutrophils.

To provide context, glucose levels in the cerebrospinal fluid (CSF) during viral meningitis are usually normal or only slightly reduced. High protein levels can occur in both viral and bacterial meningitis, but they are not as elevated as in bacterial forms, where significant inflammation and cellular debris lead to markedly high protein concentrations. A normal WBC count would not be characteristic of viral meningitis, as there would generally be some increase in lymphocyte numbers, indicative of the body's response to the viral infection. Thus, the increased lymphocytic predominance is a critical sign in differentiating viral meningitis from other types.