Case

A 30-year-old man was brought to the emergency department having been found unresponsive and cyanotic by his mother, after a presumed overdose. Paramedics identified a pulse but he was in respiratory arrest. After receiving naloxone 400 µg intramuscularly, he started breathing spontaneously. His Glasgow Coma Scale score was 14/15. He had pinpoint pupils but no other localising neurological signs. He had anterograde amnesia, and repeatedly asked questions to which he had already been provided the answers shortly before. He was disorientated in time and had minimal recall of the events that had brought him to hospital.

A CT scan of head was unremarkable and a toxicology screen was positive for cocaine and opiates.

He could not detail current events and required regular reminding of information previously provided to him, indicating short-term memory impairment.

An MR scan of …