Microbiological diagnostics and outcome in surgery for brain abscesses: a retrospective cohort study

Neurosurgical intervention is essential in the management of brain abscesses, both for optimising patient outcomes and obtaining samples. Aspiration of pus is increasingly favoured over excision, but with limited and diverging data on differences in outcome. Surgery facilitates microbiological diagnosis through cultures and molecular-based diagnostics such as polymerase chain reaction (PCR), expanding the microbiological spectrum, but with an uncertain impact on patient care.

To provide data on outcomes after aspiration and excision of brain abscesses and to provide data on the impact of PCR as an addition to cultures.

Patients aged 16 or older treated for brain abscess at a tertiary care centre were retrospectively included. Outcome was evaluated through Glasgow Outcome Score (GOS) at 3 months after discharge, GOS 1-3 considered unfavourable. Data included results from 16SrRNA PCR and Sanger sequencing analysis.

Out of 59 cases, aspiration was performed in 30, excision in 18, and 11 were managed conservatively. One patient in the excision group had an unfavourable outcome (6%) compared to nine in the aspiration group (30%), but without statistical significance. Both culture and PCR were performed on 35 samples. In 10 samples, only one method yielded positive results (5 cultures, 5 PCR). In 11 cases where both methods yielded positive results, the combination provided additional information (additional species, discordant positive).

Our study was underpowered to assess differences in outcome after aspiration or excision of brain abscesses. The addition of PCR diagnostics increases diagnostic yield in a routine clinical setting.