Immediate answer: NO

Read on to educate yourself and not be victum to rumor and uneducated bias.

Stroke, as a general medical problem, is significant as it affects more than 700,000 Americans annually. In the United States, it is the third leading cause of death, the major cause of disability and the primary reason for nursing home admission. Because of the aging U.S. population and the increased incidence of chronic illnesses, the rate of stroke will continue to increase.
    
It stands to reason that some of these people will be chiropractic patients and some will be under care at the time they stroke. This program will attempt to better define the types of strokes that are associated with chiropractic manipulation and to help develop skills in the management of this complication.

Stroke in the U.S. “Stroke” is a general term, much like “cancer.” Specifically, stroke is a loss of blood flow to the brain. There are two types of stroke:

Ischemic- loss of blood flow due to blockage.
Hemorrhagic – loss of blood flow due to bleeding, often from an aneurysm.

It is essential to understand that the ischemic type of stroke is the only one which is associated with manipulation.

Spinal manipulation is a safe and effective form of care that Smith and Carber found is utilized by over 66,000 chiropractors in the United States. Statistically, there are few complications from spinal manipulation and its safety is reflected in low premium rates from malpractice carriers. Numerous studies continue to relate the effectiveness of chiropractic manipulation for a variety of conditions. These studies are covered in detail in other courses on this website’s catalog of classes, e.g.  “Benefits of manipulation.”

The clinical problem is that a very small number of patients experience vascular complications from cervical manipulation. These complications result in ischemia of the brain stem or cerebellum (located in the posterior 1/3 of the brain) and serve as a focal point for those who are critical of manipulation in general and chiropractic in particular. Because stroke is the most serious complication from cervical manipulation, and the focus of critics of the profession, it deserves closer study.

Vertebrobasilar Insufficiency

Although Chiropractic Manipulative Therapy (CMT) is an extremely low risk procedure, it should be acknowledged that injury to the vertebral artery (VA), or stroke, is a rare but real complication that does occur even in the hands of experienced and careful clinicians. Injury to the internal layer of the VA can eventually cause occlusion of the artery and cause a clinical emergency known as vertebrobasilar insufficiency (VBI). To better understand this rare, but serious complication, a review of the vertebral artery anatomy is required.

Vertebral Artery Anatomy

Anatomical studies by Chopard have revealed the vertebral artery is “fixed to adjacent structures in the fibrous osteomuscular tunnel by means of a continuous lamina of collagen along its entire course.“ This means the VA can not slide inside the transverse foramen at each vertebral level. The vertebral artery is fixed and will be elongated as the cervical spine is rotated. Normally, this is well within the normal function of the vertebral artery.

It is theorized that excessive rotation between C1 and C2 results in tearing of the interior wall of the VA (the tunica interna). This will be discussed further in this program.

Mechanics of VA Injury

Vertebrobasilar insufficiency (VBI) is one of the more serious clinical complications that can arise from manipulation. As previously described, the vertebral arteries move laterally at C2 to enter the inferior aspect of the transverse foramen. Once they cross the transverse foramen, they move medially and follow the superior surface of the ring of the atlas. They enter the spinal canal area and turn superiorly and meet in the midline, forming the basilar artery. The ability of the atlas to rotate on the odontoid allows stretching, compression and torsion of the VA and a secondary fluctuation of the blood flow. In some individuals the atlas has the ability to cause total occlusion of the blood flow in a single VA, but symptoms will not arise because the cerebellum will receive a collateral vascular supply from the other VA.

Researchers have performed studies on the vascular flow to assess the actual impact of atlas rotation on the vascular flow in the VA. Rotation of the head will affect the flow on the contralateral artery. Thus, rotation of the head to the right will affect the left VA. It is theorized that the excessive stretching of the VA upon extreme atlas rotation and will cause a tear of the intimal or innermost layer of the VA.

VA Injury

The tear in the VA has the potential ability to cause ischemia in several ways. The tear can result in local vasospasm that serves to constrict the VA. The torn intimal wall can also be worsened by the flowing blood. The torn flap has the ability to be slowly separated from the middle layer. The enlarging flap can then either occlude the lumen of the vessel or cover the opening of another artery, such as the origin of the PICA.
Injured VA in VBI Patient

Digital subtraction angiogram is seen here of the left vertebral artery. Note the multiple areas of stenosis and decreased flow. The superior segment has been closed by an intimal flap. This VA has lost the normal characteristics of smooth caliber and flow seen in the angiogram earlier. This patient had a severe ischemic stroke.

Incidence rates of VA injury from CMT     

Manual procedures, such as manipulation, have been identified as a rare but possible cause of injury to the vertebral artery. The incidence of such injuries has been examined a number of times in the literature. As no study has the ability to count all possible cases, reviewers must perform estimates. Some studies have estimates based on reports from neurologists who encounter the injury in their practice. Other studies have proposed incidence rates based upon the incidence of the injury encountered in large clinical programs such as chiropractic colleges.

Survey of Literature Studies

Carey          1993      1:5.85 million manipulations
Dabbs         1995      1:2 million manipulations
Klougart     1996      1:900,000 manipulations
Dvorak        1985       2-3 serious events/million CMT
Hosek         1981       1:1 million manipulations
Cyriax         1978       1: 10 million manipulations

Incidence: Summary   

No matter which study is cited, or which analysis method is used, it is clear that the actual incidence rate is far lower than many complication rates for other tests or treatment procedures currently used. Nevertheless, injury to the vertebral arteries can occur and the chiropractor would be well advised to be clinically alter to the possibility that such a complication can exist.

Profile of the Stroke Patient:

One of the areas of continual concern is the identification of a patient who may have vascular complications with cervical manipulation. Opinions in these areas arise from either personal experience in reviewing such cases, reviewing a series of cases or a review of the literature. Although there are commonalities in these methods, some differences are also exist.

The age of patients involved in VA related strokes are characteristically younger than those patients with intracranial, hemorrhagic strokes. For example, Vernon noted the average age of manipulation induced strokes to be 37.9. Terrett reviewed 255 cases in the literature and the age of the patient was identified in 233 of the cases.

Terrett’s review revealed the range for such strokes was 7-87 for males, and the average age was 39.5. Female stroke victims ranged in age from 20-74 and the average age was 38.3. Thus, it seems that the average age for these patients is in the late 30s for both men and women.

The sex distribution of the stroke cases is somewhat more controversial. The majority of cases reflected in the literature are female. Vernon states the female to male ratio is nearly 2:1, with females being the larger number. This would imply that females are at a greater risk for manipulation induced stroke.

Haldeman performed a recent review of 64 cases and noted 64% of the stroke victims were female and 36% were male. The average age was 36.3 years of age with a standard deviation of 6.1 years. Some 90% of the 64 cases were younger than 45 years of age. 92% of the patients presented with cervical spine complaints. Of interest, 25% of the patients had complaints of a new type of head and/or neck pain, which was often extremely severe and had a sudden onset.

Clinical Presentation of VBI Patients

The clinical presentation of patients can be divided into symptoms before the stroke and those after the stroke. Symptoms before the stroke. Presenting complaints may vary widely as the literature frequently cites presenting symptoms which actually have no relation to the stroke. However, experience has shown that some presenting symptoms may be especially relevant.

First, as reflected in the Haldeman study, the index of clinical suspicion should rise when a patient presents with a headache/neck pain that is not normal for them. Many patients will actually state “I have never had a headache like this before.” These type of headaches seem to frequently localize to the upper cervical spine and behind an ear. This is thought to be pain from an arterial dissection.

Initial Complaints Before the Stroke
As previously noted, Haldeman reviewed 64 cases, 16 of which were experiencing new pain that was sudden and severe in onset. “Of these 16 patients, 4 complained of dizziness or vertigo and three patients had nausea or vomiting.” Two had numbness, one had numbness and tingling in the face, hands and feet and one had transient paresthesia in all limbs. One patient had tinnitis and one had visual disturbances.

Initial Complaints Before the Stroke

There are other presenting symptoms that are associated with cerebellum dysfunction and may indicate the early stages of an approaching stroke. Dizziness, unsteadiness, and vertigo are all signs that indicate the patient may be in the early stages of VBI. Chiropractors too frequently attribute these symptoms to “low blood sugar” or other causes. When in doubt, it is best to have the patient examined by others for a second opinion. This is especially true when the patient tends to have other findings such as hypertension, bruits, or history of smoking.
What about George’s test?

Various tests, including the one developed by Dr. George, attempt to screen and assess the vascular status of a patient before cervical manipulation. George’s test is performed by taking blood pressure and pulses bilaterally, checking for bruits and holding the neck in extension and rotation for 30 seconds in each direction. The maneuver was done to try and duplicate VBI signs of nausea, dizziness or nystagmus. If VBI symptoms appeared, it would be considered a positive test and the cervical manipulation would not be performed.

While the test was well intended and used for decades, it now seems that it does not work well for the intended purpose. For example, Doppler ultrasound studies have shown that head rotation can cause occlusion of a VA. On the other hand, Bolton reported on vascular screening tests being performed on patients who were known in advance to have occlusion of a VA and the performance of George’s test failed to demonstrate a positive finding. This would certainly argue against the use of George’s test.

Even listening for a bruit, which is part of George’s test, lacks sensitivity as it requires a 50% occlusion of the VA before the bruit develops. Despite these problems, many still recommend George’s test be performed. The test is cheap, non-invasive, easy to perform and a low risk procedure. Although not totally reliable, it may identify a person at risk for vascular injury. If the test fails, it still shows the doctor attempted to screen for a condition with the best test available in a chiropractic office. Questionable findings in the test would be further indication to delay the cervical manipulation for a second opinion or additional testing.

Symptoms after the stroke:

 VBI after manipulation may cause a constellation of different symptoms, depending on the location of ischemia, degree of occlusion and the degree of collateral circulation. Symptoms of ischemia in the posterior circulation include nausea, vomiting, ataxia and slurred speech. Other, less common symptoms, such as tinnitus and vision disturbances may also occur.

Clinical Presentation of VBI Patients After Manipulation

The last element of stroke symptoms concerns the timing of their onset. Symptoms of nausea, vomiting, ataxia and slurred speech will usually start almost immediately after vascular occlusion. In many cases, these symptoms will start before the patient leaves the office.

In such cases, the actions of the chiropractor within the first few minutes are critical. Any of these symptoms should be assumed to represent vascular injury, until proven otherwise. Paramedics should be summoned and DO NOT re-manipulate the patient. One must avoid the temptation to manipulate the patient in the opposite direction in the hopes of reversing the new symptoms.

Fibromuscular Dysplasia

 It should be understood that some patients may have underlying pathological changes in the artery that can make the VA’s more susceptible to injury. Fibromuscular dysplasia (FMD) is such a condition as it produces localized thickening and weakening of the arterial walls. FMD most commonly affects the renal arteries where it propensity to thicken the arterial walls causes renal artery stenosis and hypertension. The pathological changes include the production of abnormal amounts of elastic fibrils and fibrous connective tissue, along with a loss of smooth muscle in the tunica media of the artery.

The cause of FMD remains far more elusive than the radiographic changes. One theory is that it is produced by repeated dilation of the artery. Other studies reviewed 37 cases of FMD and have found a familial link, particularly with females, and cite genetics as the cause. Others believe FMD starts as a local defect in the elastic framework of the artery. No matter the cause, it has the ability to weaken arteries, including the VA and makes them more susceptible to dissection. The image on this page is a digital subtraction angiogram of the vertebral artery (late phase). Note the numerous constrictions, consistent with fibromuscular dysplasia. These multiple constrictions produce the “string of pearls” appearance. Compare this irregular lumen of the VA in this angiogram to the normal. smooth lumen in a normal vertebral artery.

Manipulation is not the only cause of VA injury and, at times, other etiologies exist. Some of which have been identified in the literature. These causes included playing tennis, star gazing, “head banging in heavy metal band”, painting a ceiling, break dancing, sitting in a barber chair, yoga, archery, wrestling, amusement park ride, turning head while driving, rapid change in head position, self-induced manipulation, and whiplash.

The preceding list outlined many activities that have been identified in the literature as a cause of vertebral artery injury. Although the activities appear to be quite dissimilar they have cervical extension and head rotation as a common biomechanical feature. Even innocuous activities such as having ones hair washed at the beauty shop, which involves extension and rotation, can cause VA injury in a susceptible patient.

Summary & Conclusions
    
• There is a rare, but real association between stroke and manipulation
    
• Vertebral arteries supply the posterior 1/3 of the brain’s blood supply
    
• The internal carotid artery supplies anterior 2/3s of the brain’s blood supply.
    
• Manipulation induced strokes are almost always associated with the vertebral arteries.
    
• Females are 2:1 more often associated with manipulation related strokes. Late 30s is the average age associated with both male and female manipulation related strokes.

• There are a number of other activities associated with the onset of VBI.
 
• There are very few symptoms which would help the doctor of chiropractic to identify the existence of a vertebral artery injury, before stroke occurs.

• Any signs of ataxia, slurred speech, vomiting… must be considered a stroke until proven otherwise.
    
• Presenting complaints of acute onset of severe atypical head pain, and pain which is located behind the ear, should be viewed as possible indicators of VA tearing.
    
• The most important action taken if a patient has ataxia, slurred speech, vomiting… is to correctly identify the presence of a stroke.
    
• Manipulation is never indicated in a patient who has paralysis, slurred speech, vomiting…

Homocysteine

   So what about other potential causes of vertebral artery dissection? Some of the most interesting research involves the effect of homocysteine on the vascular system. Dr. Rosner has written on the potential relationship between homocysteine and vertebral artery injury. Dr. Rosner states, “The newer models of arterial disease center around inflammation as being just as important a determinant as elevated cholesterol and triglyceride levels, if not more so. Plasma homocysteine has been identified as an independent risk factor for cardiovascular disease. Numerous mechanisms have been proposed to account for this anomaly, including:

(a) promotion of endothelial dysfunction of coronary resistance vessels
(b) increasing oxidative stress, known to promote myocardial dysfunction; and
(c) stimulating left-ventricular remodeling brought on by the increased cardiac fibrosis and activation of matrix metalloproteinases.”

    Dr. Rosner also noted, “With high homocysteine levels having been correlated for years with strokes and arterial dissections, it is easy to imagine how elevated levels of this metabolite may have brought on many of the vertebral arterial dissections that have hounded the chiropractic profession for years.”

The latest comprehensive review of VBA stroke and chiropractic care was found in Spine, Vol. 33, Number 45, pages 176-183. Their study spanned nine years and reviewed 818 cases of VBA strokes admitted to Ontario hospitals. The following are the key points from their study.

Key Points

• Vertebrobasilar artery stroke is a rare event in the population.
• There is an association between vertebrobasilar artery stroke and chiropractic visits in those under 45 years of age.
• There is also an association between vertebrobasilar artery stroke and use of primary care physician visits in all age groups.
• We found no evidence of excess risk of VBA stroke associated (with) chiropractic care.
• The increased risks of vertebrobasilar artery stroke associated with chiropractic and physician visits is likely explained by patients with vertebrobasilar dissection-related neck pain and headache consulting both chiropractors and physicians before their VBA stroke.