MRCP2-2886

A 35-year-old HIV-positive man presents with a two-week history of deteriorating headache, facial weakness, and visual hallucinations. He also reports experiencing eye pain for the first time. An MRI scan of his head shows multiple ring-shaped lesions that enhance with contrast. He is under regular follow-up at the HIV clinic, and his most recent CD4 count was 150 cells/mm³. What is the immediate treatment that should be initiated?