I think the hole in
is the reason for the blood clot that probably caused the stroke
. What does the cardiologist say? If your dad speaks a different language other than english, try to get speech therapy for him in that language. Sometimes, stroke patients can sing simple songs with therapy. Instead of talking, they can sing. It is sometimes easier for them. Otherwise, use picture cards, gestures, computer aided software. Keep on talking to him even if he doesn't talk back.