Actinomyces europaeus Brain Abscess in a 69-Year-Old Female Causing Irreversible Neurologic Complications

Actinomycosis is a chronic, indolent, granulomatous disease process caused by the Actinomyces genus of bacteria. More severe forms of actinomycosis include disseminated or central nervous system (CNS) infections. Actinomyces meyeri is the most common species of Actinomyces isolated from brain abscesses. A. europaeus species is commonly associated with skin and soft tissue abscesses. However, it rarely causes brain abscesses. We present an unusual case of A. europaeus brain abscess in a 69-year-old female who presented with acute encephalopathy and bilateral lower extremity weakness. She was diagnosed with left-sided mastoiditis with intracranial extension, left posterior fossa epidural abscess, and transverse sinus thrombosis. The patient's hospital course was complicated by hydrocephalus and declining neurological status. Empiric antimicrobial therapy was initiated, and the patient underwent mastoidectomy and external ventricular drain placement followed by decompression craniotomy and subarachnoid abscess aspiration. Given her poor and unchanged neurologic status, the patient was transitioned to comfort-oriented measures after shared decision-making with the family. It is crucial to identify Actinomyces as a causal agent of severe CNS infections like brain abscesses, meningoencephalitis, or subdural empyema, as untreated infections can lead to irreversible neurologic complications.