A 48-year-old man presents 30 minutes after losing consciousness and falling down. His wife witnessed the episode, and relates that he was unconscious for around 5 minutes. There were no abnormal movements; nor was there frothing at the mouth or incontinence. He has had 2 similar episodes during the past 10 months, with complete recovery afterwards. The most recent episode was 6 months ago. He also lost 12 kg of weight during this period, while his personality has subtly changed over time. A recent check up was negative for diabetes, hypertension and dyslipidemia. His surgical and family histories are unremarkable.