A rare case of cerebellar abscess caused by Nocardia cyriacigeorgica.

Background: Gram-positive opportunistic bacteria of the Nocardia species are responsible for a large spectrum of infections, such as pneumonia, skin infections, and more widespread conditions, including brain abscesses.

Case description: A 67-year-old male patient suffered from headache, gait disorder, and vertigo for a week before admission to our department. An enhanced magnetic resonance imaging scan revealed a mediosagittal hyperintense infratentorial lesion with concomitant compression of the fourth ventricle. The patient underwent surgical treatment with general anesthesia. The frozen section did not reveal any tumoral tissue but rather a purulent content. He was comatose on the 1^st postoperative day, and he underwent a follow-up computed tomography (CT) scan, which revealed triventricular hydrocephalus. The external ventricular drain was performed, and a follow-up CT scan revealed significant improvement of hydrocephalus. Matrix-Assisted Laser Desorption Ionization Time of Flight did not reveal any causative agent from the intraoperative content, but the 16s ribosomal DNA method confirmed Nocardia cyriacigeorgica. The patient was intravenously treated with ceftriaxone and trimethoprim/sulfamethoxazole and died on the 5^th postoperative day.

Conclusion: Nocardiosis presents a rare Gram-positive bacterial infection that typically affects immunocompromised hosts. Nocardia-caused brain abscesses present a significant challenge in its treatment for its atypical presentation and slow culture growth.