REPEAT LUMBAR PUNCTURE IN THE DIFFERENTIAL DIAGNOSIS OF MENINGITIS

Although monocytes eventually predominate in the cerebrospinal fluid pleocytosis caused by viral meningitis, polymorphonuclear leukocytes often are the most common white blood cells in the cerebrospinal fluid early in this disease.1 This can lead to the concern that the meningitis is bacterial, even if other laboratory and clinical findings suggest a viral etiology. The study of Feigin and Shackelford2 has resulted in widespread acceptance of the idea that repeat lumbar puncture within 6 to 8 hours almost always (in 87% of patients) demonstrates a shift to a predominance of mono-nuclear cells in patients with aseptic meningitis. This shift helps to confirm the clinical impression that antibiotic therapy is unnecessary. During a recent outbreak of viral meningitis, this evolution to a monocyte predominance apparently occurred less frequently than expected. A chart review was undertaken to evaluate this impression critically.