A 42-year-old man presents to the emergency department with a two-week history of worsening headaches, fever, and focal neurological deficits, including right-sided weakness and difficulty speaking. He reports a history of chronic sinusitis, which has been poorly managed over the years. He denies any recent trauma, surgeries, or systemic infections. On examination, he has a temperature of 38.9°C (102°F), nuchal rigidity, and right-sided hemiparesis. An MRI of the brain reveals a ring-enhancing lesion in the left frontal lobe, consistent with a brain abscess. Blood cultures are pending, and a lumbar puncture is deferred due to the risk of herniation. What is the most likely cause of this brain abscess?
