I'm not sure if this counts as a refresher type case, but it's an important one nonetheless.
The top two panels of the MRI were taken two days after admission. The lower two panels were taken two weeks after admission.
This patient presents with acute onset focal neurologic deficits. He is altered with hemiparesis, dysphagia, aphasia, ataxia, and seizures. He also has been running a high fever.
Challenge: When you perform the lumbar puncture, what diagnostic test should you order?
Image shown under Fair Use.