in loring bigelow's brain, dr. something else, something the 90-plus study is finding quite a bit-- evidence of tiny, microscopic strokes called micro-infarcts. his brain was full of them. >> kim: here is a micro-infarct. it's the hole... >> stahl: oh, right here. >> kim: ...which is basically a tiny stroke. >> kawas: so you've got all this tissue is missing. >> kim: if you find one, it suggests that you should probably look for others. and some patients may have hundreds or thousands of them. >> stahl: these microscopic strokes are insidious because people don't even know they're having them. >> kim: they can be totally silent. and slowly but surely, over time, you're picking off... you're disconnecting your cortex from the rest of the brain, and then you start to become demented. it can look just like alzheimer's disease, clinically. >> stahl: do you know anything we can do to prevent these mini strokes? >> kawas: i wish i did. but i will soon, i hope. >> stahl: kawas suspects one thing that may cause them is low