Streptococcus constellatus and Actinomyces species are known oral flora and causes of abscess formation in the brain, occurring via hematogenous, or more commonly contiguous, spread due to otitis media, sinusitis, cranial trauma, or dental procedures, with the vast majority of cases reported in immunocompromised individuals.

A 42-year-old male with no significant medical history presented with left thumb numbness, left facial droop, and slurred speech. MRI brain demonstrated a right-sided posterior frontal lobe lesion suggesting an abscess, and the patient was started on intravenous broad-spectrum antibiotics. Five days after treatment initiation, neurologic symptoms persisted with worsening left-sided weakness and new onset of severe nausea and vomiting, and the patient was transferred to the Neurologic Intensive Care Unit. CT Head showed a rapid increase in size of the lesion and surrounding edema, and the patient underwent craniotomy and mass resection yielding frank pus. Abscess cultures indicated colonization by Streptococcus constellatus and Actinomyces species. CT Head was negative for sinusitis and mastoiditis, and workup for other sources of infection, including blood cultures, was unremarkable. Patient’s nausea resolved, his weakness continued to improve, and he was discharged on intravenous penicillin and metronidazole.