A 61-year-old man is brought to ED with unusual behaviour. He uncharacteristically arrived at work an hour early and, according to his colleagues, appeared unfocused and neglectful.

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<p>A 61-year-old man is brought to ED with unusual behaviour.</p><p>He uncharacteristically arrived at work an hour early and, according to his colleagues, appeared unfocused and neglectful.</p><p>For the past day, he has experienced fatigue and a mild headache. He cannot recall any traumatic event and has no chills or fever.</p><p>On examination, his vital signs are unremarkable.</p><p>The physical and neurological examinations are also unremarkable, although he is somewhat apathetic and his attention and concentration are diminished.</p><p>Two lesions on his left middle finger are noted, which are slightly sensitive to touch.</p>