Ecca, aged 72, was brought to the emergency room by family m…

Ecca, aged 72, was brought to the emergency room by family members who were concerned because Ecca did not recognize them and seemed very confused. Ecca had been fine the day before, when the family had enjoyed a meal and had watched a movie together. She shows no sign of head injury, there is no evidence of a stroke, nor any history of neurologic disorder. This presentation is most consistent with which disorder?