Timothy C. Hain, MD Page last modified: June 18, 2009
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.
The reported incidence of severe adverse events 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. Nevertheless, the writer of this review thinks that the more common estimate is more likely to be correct.
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). Chiropractors are often unaware of this association (Haldeman et al, 2002).
|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:
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 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 lower for these small displacements than for end-range, high-speed extreme maneuvers.
The PT community advocates a test called the "vertebral artery test", which is to be done prior to neck manipulation, in an attempt to prevent a stroke. It seems to us that this test is unlikely to be sensitive to vertebral artery hypoplasia, as in our clinical experience, we have not found it to be successful in detecting this condition. Nevertheless, use of this test may keep the PT community aware and cautious about this danger.
We favor CT-angiography with 3D reconstructions, to identify vertebral arteries that are hypoplastic or asymmetric. 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.
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