Timothy C. Hain, MD Page last modified: December 5, 2015
Chiropractors can cause vertigo through several mechanisms.
In general, this is a type of "cervical vertigo", which is discussed in general elsewhere on this site. We will focus here on the types of injuries to the vertebral arteries that might occur during high-impact manipulations.
As a bottom line, we suggest that dizzy people avoid seeing chiropractors that snap their neck or turn the head far to one side for prolonged periods of time.
The reported incidence of severe adverse events including stroke after chiropractic manipulation of the neck varies widely and the estimate varies according the source. It may be as high as 1:4500 according to the PT literature (Mann and Refshauge, 2001) or as infrequent as 1:1 million according to the chiropractic literature (Vikers and Zollman, 1999). Physical therapists and chiropractors are competitors, and it seems to us that neither of these estimates are free from bias. The writer of this review thinks that the more common estimate is more likely to be correct. According to Wynd et al (2013), the quality of papers about this subject is poor. They reviewed 43 articles that reported 707 instances of stroke attributed to chiropractic manipulation. Hmmm. Haynes et al (2012) also felt that "conclusive evidence is lacking for a strong association between neck manipulation and stroke". Well -- what about good evidence or a moderate association ?
There is a substantial conventional neurological literature showing that chiropractic manipulation of the neck is associated with a substantial increased risk of vertebral artery territory stroke (Rothwell et al, 2001; Smith et al, 2003; Vibert et al, 1993; Albuquerque et al, 2011; Jones et al, 2015). Chiropractors are often unaware of this association (Haldeman et al, 2002).
The chiropractic community has, in their literature, stated "We found no significant association between exposure to chiropractic care and the risk of VBA stroke. We conclude that manipulation is an unlikely cause of VBA stroke." (Kosloff et al, 2015). We find it very hard to believe that rapid manipulations of arteries that traverse bones in the neck, are not associated with greater risk of vertebral artery stroke. We have encountered cases where patients saw a chiropractor, and then were admitted to the ER a few hours later with a stroke. Or similar situations where stroke followed roller coaster rides, or diagnostic tests where the head is turned far to one side. While there are many other causes of stroke, we think that it is very clear that manipulation of arteries can trigger stroke. One would imagine that the chiropractic community has a very strong motivation to protect their profession's image, and the possibilities of bias are substantial. So to sum it up, we just don't buy the chiropractic literature's assertions that there is no risk from their procedures. We think that manipulation must increase risk of stroke. We can't imagine any way that it would decrease risk of stroke. The question that remains is how much risk does it add ?
|The vertebral arteries combine to form the basilar artery||Narrowing of the left vertebral artery (right side of picture) attributed to dissection. Image was obtained after a chiropractic manipulation was followed by vertigo.|
The main concern with chiropractic manipulation is that there may be injury to the vertebral artery. The vertebral arteries begin in the neck generally taking their origin from the subclavian arteries. They next enter the bones of the neck (vertebrae) at C5-C6, and then ascend upward through holes in the bones called "transverse foramina". Between the top 2 vertebrae, C2 and C1, the vertebral arteries move laterally. Next they enter the skull, and eventually join together to supply the brainstem and cerebellum.
The vertebral arteries are thought to be most vulnerable above their exit from C2 where they have several points of fixation. They are fixed at the C1 transverse foramen, the groove on the superior aspect of C1, and the dura intracranially. (Mann and Refshauge, 2001).
Injuries to the vertebral artery might include one or several of the following:
- Vertebral artery dissection causing ischemia and/or stroke
- Damage to vessel wall through pressure
- Elongation of the "stiff" vertebral arteries by rotation.
- Temporary blockage causing ischemia
- "bruise" to the artery causing a clot to form and stroke
- Injury to the subclavian artery by massge of the neck area (there was one report of this).
- Dissection of the carotid arteries.
According to Mann and Refshauge (2001), the features that are most likely to account for the risk are the force and amplitude of the neck maneuver. The C1/C2 segment of the neck is normally more mobile than the other joints, and the vertebral artery makes an abrupt turn as it exits the C2 transverse foramen. Higher risk situations probably involve extreme maneuvers - -large amplitude, at the end of range, and high speed (Mann and Refhauge, 2001).
There are also sporadic reports of damage to the subclavian arteries (from manipulation around the shoulder) (Park et al, 2013), and carotid artery dissections (Carprieaux et al, 2012).
There are newer devices being used in the chiropractic community for manipulation, that cause small displacements of the vertebrae. The risk of these devices for vertebral artery injury is presently unclear. It would seem plausible that the risk would be much lower for these small displacements than for end-range, high-speed extreme maneuvers.
Of course the best way to avoid a stroke from chiropractic manipulation is to simply avoid having the manipulation done. Our suggestion is to avoid people who "snap" your neck, if you are dizzy.
The PT community often does some more gentle head movement, and advocates a test called the "vertebral artery test", which is to be done prior to neck manipulation, in an attempt to prevent a stroke. We use this test in 100% of our new patient visits - - looking for cervical vertigo -- and it is almost never positive. In particular, even in people who are missing one vertebral artery, this test is nearly always normal. It seems to us that this test probably has no predictive value for stroke, but use of this test may keep the PT community aware and cautious about the risk of stroke from neck manipulatio.
We favor CT-angiography with 3D reconstructions, to identify vertebral arteries that are hypoplastic or asymmetric. The main difficult with this procedure is that in essence, a computer reconstruction "guesses" where the arteries may be (or not be), and it is not a good situation when you have to rely on a computer's guess work. More accurate, but needing more skill, is having a good radiology review the "source" images carefully.
MRA has advanced greatly in recent years, and may be superior to CTA in many cases.
In a person in whom there is a strong chance of dissection, selective vertebral angiography may be appropriate. See the cervical vertigo page for a longer discussion about the radiology of this condition.
|CT angiogram. Left vertebral (left lower) is large and dominant. Right vertebral (right lower) is small and hypoplastic. This is the same case as shown in the selective vertebral angiogram below.|
A 45 year old woman went to a chiropractor for treatment of neck pain. The chiropractor "snapped" her neck. After this occured, the woman lost hearing on one side, temporarily. Investigation revealed that one vertebral artery was atrophic.
Selective Vertebral Angiography - -demonstrates that left vertebral (on left) is large and normal, while right vertebral artery is small and does not fill the basilar artery. Note the normal "kink" that occurs in the vertebral artery around C1-C2.
Comment: About 2% of vertebral arteries are hypoplastic. When this occurs, rotation of the head to the end of range may block the other side and cause brainstem ischemia.