Value of second lumbar puncture in confirming a diagnosis of aseptic meningitis. A prospective study.

In patients with viral meningitis, polymorphonuclear leukocytes sometimes predominate in the CSF on initial examination. In a prospective analysis of this phenomenon, 16 consecutive patients with viral meningitis were followed up with serial CSF studies. The percentage of polymorphonuclear leukocytes showed a significant fall between initial and second examinations (41.75 +/- 27.0 to 8.6 +/- 8.78 [mean +/- 2 SD], P less than .001), while total WBC counts and the protein and sugar content levels remained unchanged. Based mainly upon this "polymorph shift," antibiotic therapy was correctly withheld from 100% of patients reexamined. On subsequent examinations, the percentage of polymorphonuclear cells remained low. All patients recovered completely without any specific treatment. In otherwise healthy subjects with the aseptic meningitis syndrome, antibiotic therapy can be withheld even when polymorphonuclear cells predominate on initial CSF examination. If suspicion arises regarding the diagnosis, another examination will demonstrate a significant fall in polymorphonuclear cells if the initial impression was correct.