Isolated Cerebellar Abscess by Nocardia cyriacigeorgica in an Immunocompetent Patient: A Case Report and Systematic Review.

Nocardia is a Gram-positive bacillus characterized by branching filaments, accounting for approximately 2% of all cerebral abscesses. It predominantly affects immunocompromised individuals. Central nervous system nocardiosis is less frequently reported and carries a poorer prognosis. Clinical diagnosis is challenging due to its heterogeneous presentation, which typically follows an insidious course and lacks systemic inflammatory response signs. We present the case of a 46-year-old woman who presented with a 3-month history of suboccipital headache, accompanied by gait ataxia and dizziness for 7 days. Neurological examination revealed upbeat nystagmus in the right eye, dysarthria, right-sided dysmetria, and lateropulsion. Magnetic resonance imaging revealed an irregular, multiloculated, ring-enhancing cystic lesion in the right cerebellar hemisphere with evidence of restricted diffusion. The abscess was drained via stereotactic navigation, and culture identified Nocardia cyriacigeorgica . Targeted antibiotic therapy was initiated according to sensitivity testing, resulting in marked clinical improvement and resolution of the patient's cerebellar symptoms. This case presents an isolated cerebellar abscess caused by N. cyriacigeorgica in an immunocompetent patient, highlighting the diagnostic and therapeutic challenges involved.