I had never heard about this phenomenon myself until a few years ago, when I heard it mentioned on an episode of Alan Alda’s
Scientific American Frontiers. I questioned his accuracy, but I quickly found confirmation in the medical literature.
A typical case was that of 24 year old
Kristi Bedenbaugh who saw her chiropractor for sinus headaches. During a neck manipulation she suffered a brain stem stroke and she died three days later. Autopsy revealed that the manipulation had split the inside walls of both of her vertebral arteries, causing the walls to balloon and block the blood supply to the lower part of her brain. Additional studies concluded that blood clots had formed on the days the manipulation took place. The chiropractor later paid a $1000 fine.
The two vertebral arteries run straight up the back of the neck passing through holes in the sides of each neck vertebra. When the head turns, the “tethered” artery is drastically kinked:
Because of this kinking, it is particularly susceptible to injury. Even a simple thing like extending the neck back over the basin for hair washing at the beauty salon has been known to cause a stroke. The artery is elastic, but with hardening of the arteries, with cholesterol plaques, with trauma (like automobile accidents) or simply with rapid stretching, the delicate lining of the artery can tear. It is easy to imagine how a rapid, forceful thrust by a chiropractor could cause damage.
Sometimes the damage is immediate and the patient collapses on the chiropractor’s table. Sometimes mild symptoms start immediately and progress after the patient leaves the chiropractor’s office. Sometimes the tear is a small one and it clots over; then days later the clot breaks loose, travels to the brain and causes a delayed stroke. By this time, the patient may not connect his sudden collapse to the previous visit to the chiropractor.
Chiropractors are well aware of the risk. They discuss it in their journals and online forums. They have tried to find ways to screen patients for high risk, but there is no reliable way to do so.
Strokes are a major reason for chiropractic malpractice insurance payouts – 9% of claims paid by the major chiropractic insurer in 2002, the only year for which I was able to find statistics. Some chiropractors are now asking patients to sign an informed consent form before manipulations. If asked, most chiropractors downplay the risk, saying it occurs in less than one in a million manipulations. Many (perhaps most) chiropractors do not mention the risk at all.
Most alarming: some chiropractors perform these neck adjustments with no warning and without permission. I met a woman who still walks with a limp and has other residual impairments from a chiropractic stroke. She went to her chiropractor for a shoulder problem and thought he was going to massage her shoulder muscles. She did not want him to manipulate her neck, did not give him permission, and didn’t realize what he was doing until he suddenly twisted her neck. She collapsed on the table and nearly died.
How often can a stroke be attributed to neck manipulation? We really don’t know. Estimates have varied from one in ten million manipulations to one in 40,000. I should clarify that only one specific type of stroke, basilar stroke, has been linked to chiropractic.
It has been estimated that about 20% of all basilar strokes are due to spinal manipulations. This would work out to about 1300 a year in the U.S. But we just don’t know, because it has not been properly studied. Carotid artery strokes have also been reported after chiropractic treatments. Chiropractors do not follow up on every patient. Patients who have delayed strokes may never see their chiropractor again, so chiropractors would naturally tend to underestimate the risk. Many of these diagnoses are missed because the vertebral arteries are not typically examined on autopsy.