my 55 year old downs syndrome brother has had about a dozen episodes over the past 3 years or so where he stiffens up and then goes limp and seems to have a very mild weakness on his right side for about 15 to 60 minutes.........he also is suffering some signs of dementia which is prominent in the family.........he also had a stroke at age 28 and another mild one 3 years ago...........he has recently had dvt s in both his legs and as he is not a candidate for blood thinners, had a mesh filter inserted into the vena cava.........is he having mini stokes or seizure activity........