Unveiling a Rare Central Nervous System Infection: A Case of Primary Cerebral Actinomycosis

Abstract Actinomycosis is a rare, chronic granulomatous infection caused by Gram-positive anaerobic bacteria belonging to the Actinomycetaceae family. Central nervous system (CNS) involvement is quite uncommon, usually occurring secondary to blood-borne dissemination or direct invasion from an adjacent infection. Primary actinomycosis of the brain is extremely rare, with few reported cases in published literature. We present a 59-year-old male with primary CNS actinomycosis. A 59-year-old male presented with a 7–8-month history of trismus associated with right temporal swelling. He also gave a history of multiple episodes of generalized tonic–clonic seizures. The patient had a history of head trauma 25 years ago, for which he underwent surgery. Examination revealed a firm, tender temporal mass with an underlying bony defect. Magnetic resonance imaging of the brain showed multiple ring-enhancing lesions in the right temporal lobe with dural thickening, suggestive of an infective etiology. Surgical intervention revealed a firm mass involving the temporalis fascia, muscle, and dura with intracranial extension. Histopathology confirmed actinomycosis with dural and brain abscess formation. The patient initially improved with intravenous antibiotics and was discharged but presented 2 months later with pus discharge from the surgical site. A second surgery was performed to remove the titanium mesh and the underlying granuloma, followed by another 8-week oral antibiotic course. Due to its rarity and nonspecific presentation, cerebral actinomycosis is often misdiagnosed. A high index of suspicion, timely surgical intervention, and prolonged antimicrobial therapy are essential for successful management. Early recognition and comprehensive treatment can significantly improve patient outcomes.