Stroke Bouncing Back, BP Medicines Adjusted, Mentally Slipping Slightly. Suggestions ?

My father in law is 88. He had a stroke several years ago but seemed to bounce back well. No apparent leftover affects from it. He uses a walker but over the past year or two we've noticed he's had these "spells" (for lack of a better term). They have become very frequent recently. during these, he will stare off into space, one of his hands will shake, if he's standing his legs will shake and he'll go down. they sometimes happen when he's sitting lately even. they can last from 15-30 seconds but this last one lasted about 4 minutes. his doctor has adjusted his bp meds but says that there's nothing they can do for him. their concern is that he'll fall and hit his head and injure himself. they feel that they are "mini strokes" of sorts. Mentally, he's slipping a little but he's pretty much together. He's a smart guy and very organized with finances, etc. My 85 year old mother-in-law has been handling this in assisted living and covering for him as she's afraid they'll suggest a nursing home soon. any thoughts?