Brain Abscess Caused by Oral Cavity Bacteria: A Nationwide, Population-based Cohort Study

Oral cavity bacteria are the most frequent etiology of brain abscess. Yet, data on the clinical presentation and outcome are scarce.Nationwide, population-based study comprising all adults (≥18 years) with brain abscess due to oral cavity bacteria in Denmark from 2007-2020. Prognostic factors for unfavorable outcome (Glasgow Outcome Scale of 1-4) were examined by modified Poisson regression to compute adjusted relative risks (RR) with 95% confidence intervals (CI).Among 287 identified patients, the median age was 58 years (interquartile range 47-66) and 96/287 (33%) were female. Pre-existing functional impairment was absent or mild in 253/280 (90%) and risk factors for brain abscess included immuno-compromise 95/287 (33%), dental infection 68/287 (24%), and ear-nose-throat infection 33/287 (12%). Overall, a neurological deficit was present in 246/276 (86%) and in combination with headache and fever in 64/287 (22%). Identified microorganisms were primarily Streptococcus anginosus group, Fusobacterium, Actinomyces, and Aggregatibacter spp., and 117/287 (41%) were polymicrobial. Unfavorable outcome occurred in 92/246 (37%) at six months after discharge and was associated with antibiotics before neurosurgery (RR 3.28, 95% CI 1.53-7.04), rupture (RR 1.89, 95% CI 1.34-2.65), and immuno-compromise (RR 1.80, 95% CI 1.29-2.51), but not with specific targeted antibiotic regimens. Identified dental infection was associated with favorable prognosis (RR 0.58, 95% CI 0.36-0.93).Brain abscess due to oral cavity bacteria often occurred in previously healthy individuals without predisposing dental infections. Important risk factors for unfavorable outcome were rupture and immuno-compromise. However, outcome was not associated with specific antibiotic regimens supporting carbapenem-sparing strategies.