dr. clifford segal says it's rare but can happen when necks are hyper extended. >> you could possibly tear or irritate the posterior circulation. >> reporter: doctors recommend using towels to prop your head up so it's tilted no more than 20 degrees. they also say you can face the basin, flip your hair over, and wash it that way. smith is a single mom. two years later she still has dizziness and vision loss. ago. but worst of all doctors say if she suffers a second stroke, she could die. warns others to be careful. >> who knew? that was andrea fuji reporting. other things that can trigger that include roller coaster rides, dentist chairs, sit-up exercises, and yoga. but doctors remind us suffering a stroke from any of these things is extremely rare. >>> the next big movie blockbuster could be chinese. >> beijing's movie business is getting help from big american stars like matt damon. we will show you how the chinese and hollywood are working together to create the next big film. >>> no need to wait until st. patties day to celebrate. i'll show you a wee bit of river dance. >>> and a littl