A 70-year-old man is brought to the hospital by his wife due to increasing vagueness and a headache the day before. He has a history of Parkinson’s disease and has been consistent with his medication. He was born in Russia and has been exposed to tuberculosis in his younger years. He immigrated to the UK twenty years ago and has not traveled abroad in the last year. On examination, he is very sleepy and unable to recall his history. His chest is clear, but he has a temperature of 38.2ºC. His blood work shows elevated CRP and WBC levels. A lumbar puncture reveals mononuclear cells. CT head shows no acute intracranial or extracranial bleed. What is the likely diagnosis?