Streptococcus anginosus group brain abscesses and subdural empyemas: exploratory compartment-specific phenotypes and discharge outcomes in a single-center retrospective cohort study.

BACKGROUND

Intracranial suppuration caused by the Streptococcus anginosus group (SAG) includes brain abscess and subdural empyema, but compartment-specific phenotypes and short-term outcomes remain incompletely described. We characterized clinical, radiological, and microbiological features and explored factors associated with poor discharge outcome.

METHODS

We conducted a single-center retrospective cohort study of patients with imaging-confirmed intracranial suppuration and SAG identified by culture and/or metagenomic next-generation sequencing from October 2020 to October 2025. Cases were classified as intracerebral (n = 39), subdural (n = 6), or mixed (n = 7). The primary outcome was Glasgow Outcome Scale (GOS) at discharge; GOS 1-3 defined poor discharge outcome. Analyses were descriptive, with exploratory univariable logistic regression.

RESULTS

A total of 52 patients were included. Patients with subdural empyema were younger and had numerically lower admission functional status than those with intracerebral infection, whereas subdural and mixed-compartment infections showed higher inflammatory-marker levels. Ventricular involvement was uncommon (5/52, 9.6%) and was observed more frequently among patients with poor discharge outcomes in unadjusted comparisons (5/12 vs. 0/40). Complete ring enhancement was confined to intracerebral cases, and S. intermedius was the predominant species. At discharge, 12 patients (23.1%) had poor outcomes, including six in-hospital deaths (11.5%). Lower admission KPS and fever were exploratory univariable associations with poor discharge outcome.

CONCLUSIONS

This study describes compartment-specific clinical, imaging, and microbiological features of Streptococcus anginosus group brain abscesses and subdural empyemas. Ventricular involvement may be a marker of severe disease, but all findings should be interpreted as exploratory and require validation in larger multicenter studies.