Infections of central nervous system (CNS) include a broad group of conditions and pose a particular challenge to physicians, especially in immunocompromised individuals. This case refers to a 26-year-old male patient with a history of smoked hashish and drug abuse admitted to the infectious disease department with hemiballismus of left hemibody and a positive HIV serologic test. A magnetic resonance imaging (MRI) study showed lesions at lower left and right cerebellar hemisphere, one of them thalamus - mesencephalic suggesting an opportunistic infection or an HIV associated encephalopathy. Lumbar puncture, brain biopsy and successive neuroimaging were not conclusive for one disease and despite the use of directed therapy for cerebral toxoplasmosis, meningeal tuberculosis, anti-retrovirals and sedative medication, after over 6 weeks of hospitalization pallidotomy was performed. After 5 months of oral and surgical treatment the patient showed clinical, immunological and radiological recovery.