7th June 2023

A 68-year-old retired plumber presents to hospital with a generalised tonic-clonic seizure

A 68-year-old retired plumber presents to hospital with a generalised tonic-clonic seizure. On further questioning, he reports a six-month history of unintentional weight loss. He is an ex-smoker, and his past medical history is significant for chronic obstructive pulmonary disease and benign prostatic hypertrophy. He lives with his wife and is usually independent in all activities of daily living.

His family reported a three-week history of visual hallucinations followed by impaired short-term memory. He has a lumbar puncture, and his cerebrospinal fluid shows an elevated white cell count. MRI brain shows abnormal signal in the temporal lobes bilaterally. A viral PCR screen on his CSF comes back as negative.

Which of the following tests is likely to provide the correct diagnosis?