In their study, Rothwell and colleagues analyzed patient records for all of Ontario's hospitals from 1993 to 1998. They also analyzed insurance billing records to determine which patients had used chiropractic services before having the stroke. Researchers identified 582 people who had been admitted to hospitals with vertebrobasilar stroke and compared them with 2,328 people from Ontario's general population who had no history of stroke. However, Rothwell cautions, her data is somewhat limited because it relies on hospital records, which could contain errors. It's quite possible to go in with a neck complaint and not have a manipulation done.
Some patients go to a chiropractor without a neck complaint and have a neck manipulation done.
Whiplash from a car accident can cause similar trauma to arteries, for instance. In others, something mild may have happened, but the blood vessel was already weakened. Powers says that for years he has advised against chiropractic manipulation. They're reporting that there seems to be a relationship between recent manipulation and stroke. If there's no benefit, then any risk is not worthwhile.