This is an interview with Dr. David Sherman, spokesperson for the American Heart Association (AHA), concerning the recent AHA news release of a survey of neurologists that stated stroke after cervical manipulation is a "small but significant risk" (see March 11th issue of "DC"). The survey results were presented at the 19th International Joint Conference on Stroke and Cerebral Circulation in San Diego, California.
"DC": Could you explain the survey on cervical manipulation?
Dr. Sherman: A group of neurologists at Stanford decided to poll neurologists in the state of California as to whether or not they had, in their own practices, come across a patient who had suffered a stroke that they felt was related to cervical manipulation, and the stroke had come on within 24 hours. They then sent a mailing to California neurologists from a mailing address list provided by the American Academy of Neurology. They received replies from, I believe, 177 neurologists, which represents a little over one-third of those who were surveyed. On this questionnaire they inquired whether they had seen a stroke that they felt was related to cervical manipulation. These neurologists who responded reported a total of 56 strokes that they had seen that it was their opinion had occurred within 24 hours of a cervical manipulation.
"DC": From what we understand, the results of the survey weren't verified. Is that correct?
Dr. Sherman: Were not verified?
"DC": Right, that the cases the neurologists reported as stroke from chiropractic cervical manipulation were not verified.
Dr. Sherman: That is correct. Nobody went back to track down the charts of individual patients and verify them, that's correct.
"DC": Would this be considered a retrospective study or would it not qualify for that?
Dr. Sherman: Yes, this would be a retrospective study.
"DC": The press release states that the researchers surveyed 177 California neurologists and that the response rate was 36 percent. What percentage response rate was needed to have viable results?
Dr. Sherman: I don't remember that they stated or had a predetermined number of responses that they were going to insist on before they considered reporting the results or not. It wasn't stated.
"DC": But normally in research work, would a 36 percent response rate be considered adequate to draw conclusions, or would that be considered less than adequate?
Dr. Sherman: I think you have to be cautious about the conclusions that you would draw. Certainly one could imagine that the people who responded might be the ones who were more likely to have seen someone with a stroke related to a neck manipulation, and the ones who didn't respond you might expect to be more likely to be people who hadn't seen someone. So in that sense, you might speculate that this was possibly an overestimation. I don't know the answer to your question.
"DC": Without verifying the results, we would have to call the survey anecdotal.
Dr. Sherman: Yes, I think these are anecdotal results.
"DC": Our copy of the abstract from Dr. Carlini (editor's note: one of the researchers who headed the survey) states, "The above is an abstract. The actual article will probably not be available until November or December 1994."
Dr. Sherman: I don't know if it has even been submitted for consideration for review by a journal.
"DC": From what we understand it isn't finished yet and subsequently couldn't be submitted.
Dr. Sherman: I don't know.
"DC": At the San Diego conference, the American Heart Association released a total of eight news items. Were most of the news releases dealing with studies that had an anecdotal part to them or were somewhat anecdotal?
Dr. Sherman: The news releases to a large extent are selected based on their subject matter and the likelihood that the subject matter might be of interest to a lay audience. That's my interpretation anyway. Certainly, I did part of the press conference and while they might have sent out eight, I probably pointed out 30 or 40 abstracts that I thought that the press might be interested in, and I picked them out because, from my experience, they were things the public might be interested in. So if it's a new drug that has some potential benefits, I think that the public is generally interested in that; if it has something to do with a new surgical procedure, angioplasty, they may be interested in that. They are typically not that interested in the basic experimental, mechanistic type work, which most news media would find boring.
"DC": Do you know if there is some kind of a follow up study planned to this survey?
Dr. Sherman: I really don't know. As I recall, they didn't mention any plans to try to do a larger survey or extend this or do anything else with it. But I really don't know.
"DC": When you were reviewing the different studies and deciding which among them would be AHA press releases, did you note that some of the studies were high caliber science, whereas others were low-caliber, anecdotal, not reviewed, and with a small percentage of respondants? Is this a typical cross-section or is the survey on manipulation notably below par?
Dr. Sherman: I think you look at each study based on its design, its strengths and weaknesses, and certainly this study, as you pointed out, is a retrospective study and wasn't validated. It's anecdotal. Nevertheless, it was obviously of interest to the press in terms of selecting abstracts to mention. We pointed out abstracts for angioplasty, for example, that involved less than 10 patients. You can't, I don't believe, make an arbitrary decision that we're only going to present or point out to the press abstracts that contain hundreds of patients and double-blind randomized trials and that sort of thing.
"DC": Some people in the chiropractic profession are rather reactive to this and they wonder why this particular survey was deliberately focused at chiropractic. Rather than looking at cervical manipulation in general, chiropractic was isolated from osteopathic manipulation or other manual manipulators. Do you have any response to that?
Dr. Sherman: I don't know really how the questionnaire was presented. I don't know if it specifically said chiropractic manipulation or whether it included questions about other types of neck movements or manipulation.
"DC": In both the press release from the American Heart Association and in the abstract, it specifically states cervical chiropractic manipulation.
Dr. Sherman: Right, but it doesn't answer the question of what was requested when the survey was sent out. I don't know if the questionnaire was confined to chiropractic manipulation or if they were asking for strokes related to any sort of head movement.
"DC": So there could be some confusion in that area.
Dr. Sherman: Yes. It would make a difference as to what was asked for.
"DC": Have you seen some of the reactions from the press on this? We've seen headlines in publications ranging from, "Chiropractors could kill you," to "Doctors warn that sudden neck movements can trigger strokes."
Dr. Sherman: I haven't seen any of them, no.
"DC": The press has taken this and run with it in a dramatic way.
Dr. Sherman: That is not uncommon. I have a whole pile of notes on my desk about other press releases that were distorted, and now poor patients are calling up and asking for drugs that have nothing to do with what they've got. That is sort of par. I'm amazed when it comes out the same way you say it.
"DC": In looking at the survey and how it focused on the chiropractic profession, you have no sense that there is any intention to deliberately target chiropractic?
Dr. Sherman: I don't think so. As a matter of fact, I thought that they made an attempt to point out in their presentation that they were making no sorts of judgments about how frequent this occurs as a complication and, as a matter of fact, I thought that they went out of their way to point out that the evidence would suggest that it's a very rare complication. But they pointed out that getting precise data about how frequently it occurs is very difficult and they acknowledged the weakness of this particular way of doing it. But that doesn't make very good press to say it happens but it is probably extremely rare.
"DC": There are some studies on cervical manipulation going on by some researchers that are in the chiropractic field, one being done by a DC, PhD, and one by a methodologist. Could you see an opportunity in a future AHA conference where someone from the chiropractic profession would be able to present such a study, if it were a bit more detailed?
Dr. Sherman: Absolutely.
