This study sought to describe the clinical presentation of normocellular community-acquired bacterial meningitis in adults.

Using the prospective, nationwide, population-based database of the Danish Study Group of Infections of the Brain, the study identified all adults with normocellular community-acquired bacterial meningitis who were treated at departments of infectious diseases in Denmark from 2015 through 2018. Normocellular community-acquired bacterial meningitis was defined as a cerebrospinal fluid leukocyte count of up to 10×10⁶/L combined with detection of bacteria in the cerebrospinal fluid. Outcome was categorized according to the Glasgow Outcome Scale at discharge.

Normocellular cerebrospinal fluid was observed in 12 of 696 (2%) patients with community-acquired bacterial meningitis. The median age was 70 years (range 17 to 92 years), and 8 of 12 (67%) patients were male. All patients had symptoms suggestive of community-acquired bacterial meningitis and pathogens identified by culture (Streptococcus pneumoniae, n=10; Staphylococcus aureus, n=1) or polymerase chain reaction (Neisseria meningitidis; n=1) of the cerebrospinal fluid. Bacteremia was found in 9 of 12 (75%) patients, and 1 of 12 (8%) presented with septic shock. None of the patients had serious underlying immunocompromising conditions. The median times from admission to lumbar puncture and meningitis treatment were 2.5 hours (interquartile range 1.1 to 3.9 hours) and 2.6 hours (interquartile range 0.9 to 22.8 hours). In 3 of 11 (27%) patients, empiric treatment for community-acquired bacterial meningitis was interrupted by a normal cerebrospinal fluid cell count. The overall case-fatality rate was 3 of 12 (25%); meningitis treatment was interrupted in 1 of these patients, and 8 of 12 (67%) had a Glasgow Outcome Scale score of 1 to 4 at discharge.

Normocellular community-acquired bacterial meningitis is not very common, but it is important to consider and may be associated with a pneumococcal cause.