A 25-year-old man is brought in from the Language School due

to abnormal behaviour. His tutor noted that he was behaving oddly - distracted

in class, confused and disorientated to time, place, and person.

On examination, you find it hard to engage him. He is not fluent in English. You cannot

complete a neurological examination due to his inattention. He can focus on you

and others but only for a short period of time. He has no evidence of auditory

or visual hallucinations.

His vital signs: HR 78 bpm, BP 110/70 mmHg, temp 37°C, BSL 5.5 mmol/L.

What is your differential diagnosis at this stage?