my 82 year old father, caucasian, has experienced numbness in his right cheek and numbness in his right arm. he is at a hospital in B'ham, AL. They are considering an MRI, but he has a pace maker that is giving the doctors pause at the moment. We are 30hours after the episode began. He is having trouble writing with his right hand today. The numbness is still there. He had a previous event similar to this in April. MRI and CAT scan at that time were clear. THis event has been more severe and lasted longer. He had heart surgery in December 2016. What is likely cause ?