It was the return of Bruce Willis’s childhood stutter that gave his wife Emma Heming Willis her first hint that something was wrong. “Never in my wildest dreams did I realize that was a symptom,” she told an audience in Toronto on Tuesday. Bruce Willis, 70, had long since overcome the speech impediment that once saw him tagged with the mocking schoolyard nickname “Buck Buck,” in 1960s New Jersey. But this returning stutter, which coincided with other communication problems in his late sixties, was a sign of the progressive aphasia, or loss of language, that would later be...