LOSS OF BLOOD FLOW TO THE BACK OF THE BRAIN (VERTEBROBASILAR ISCHEMIA)
Excerpted from HOW TO PREVENT YOUR STROKE by J. David Spence, MD. Reprinted with permission from Vanderbilt University Press. To order the book, call 800-627-7377 or visit
Reduced blood flow in the territory of the vertebral arteries or the basilar artery can be recognized by a particular constellation of symptoms. The symptoms in a particular case will depend on what part of the brainstem and/or occipital cortex and/or mesial temporal lobe are involved: If the occipital lobes are involved, there will be visual symptoms (flashing lights, zigzag lines, loss of vision). If the nearby cortex that serves visual association is involved, there may be impaired visual processing; for example being unable to recognize familiar faces, or becoming lost in familiar surroundings. If the mesial temporal lobe is involved, there could be impairment of short-term memory that may present as transient global amnesia, or if there is infarction on both sides, permanent impairment of short-term memory.
Figure 2.3 Brainstem and cranial nerves.
During an episode of transient global amnesia the patient may be alert and seemingly functioning normally, but unable to record ongoing memory; typically the person, though awake and seemingly functioning well, will ask the same question over and over again (eg. "why are we here?" , or "what are we doing"), and will have no recollection of the entire episode, which may go on for hours.
Involvement of the top part of the brainstem (the midbrain) will commonly present with double vision; involvement in the middle part (the pons) commonly presents with vertigo and/or numbness in the face. Involvement in the lowest part (the medulla) may lead to thickening of speech (dysarthria), and trouble with swallowing. Numbness and weakness on one side of the body or both sides of the body may occur when lesions in any part of the brainstem affect nerves running from the spinal cord to the brain, or vice-versa. Involvement of the cerebellum can cause clumsiness, and staggering.
Ischemia of the cranial nerve centers (nuclei) and their connections in the brainstem may cause facial numbness and weakness, double vision, difficulty swallowing, thickness of speech, vertigo, tinnitus (ringing in the ears), and deafness.
Thus, in patients who have a TIA, the symptoms point to which part of the brain that is involved, and to the artery that is involved in causing the disruption of blood flow to part of the brain. This determines what treatment will be needed to prevent a stroke.
Strokes due to neck injury
A special cause of stroke, that is more common in young people, is called dissection of the arteries. The inner lining of the artery peels off and rolls up, and can block the artery, or can be a place where clots form and then break off and embolize downstream.
Dissection of an artery may be spontaneous, or may be related to injury. The vertebral arteries, so called because they run up through channels in the bones of the neck, are particularly susceptible to injury at the top of the neck, where they make a sharp turn and go up through the hole at the base of the skull through which the spinal cord connects to the brainstem (the "foramen magnum"). At that point they are susceptible to injury in car crashes or chiropractic manipulation.
Figure 2.4 Mechanism of injury of the vertebral arteries in motor vehicle crashes or with chiropractic manipulation.
Although strokes due to chiropractic manipulation are perhaps the best known, my experience has been that motor vehicle crashes are a more common cause of these strokes(4). Even minor neck injuries sustained in yoga, swimming, or extending the neck over the edge of a hairdressser's wash basin(5) have led to these strokes. Although strokes due to chiropractic are seldom missed, the ones that happen after car accidents are seldom diagnosed. If you are in a car accident or undergo a neck manipulation, and then have symptoms of vertebrobasilar ischemia (described above), such as vertigo, flashing lights in the vision, loss of consciousness or periods of amnesia, you should be aware that you may be having TIA's due to injury to your vertebral arteries. The delay between the neck injury and the TIA or stroke can be months or in rare cases even years.
Chiropractors say that strokes from neck manipulation are very rare, about 1 in a million manipulations. Most stroke experts see so many of these strokes (we now see about 1-2 per month in our Urgent TIA Clinic) that they seem more common, but perhaps there are more manipulations than we realize. In any case, even if the risk is small, to me it isn't worth taking: randomized clinical trials show that physiotherapy is as effective as chiropractic(6;7), and without neck manipulation there is less risk of stroke. Massage therapy is also very helpful for headaches, which are most often due to spasm of the neck muscles. That kind of headache is particularly common in people with vertigo, because they are using their neck muscles to try to stop the world from spinning.
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(4) Beaudry M., Spence J.D. Motor vehicle accidents: the most common cause of traumatic vertebrobasilar ischemia. Canadian Journal Neurological Sciences 2003;30:320-5.
(5) Weintraub M.I. Beauty parlor stroke syndrome: report of five cases. Journal of the American Medical Association 1993;269:2085-6.
(6) Cherkin D.C., Deyo R.A., Battie M., Street J., Barlow W. A comparison of physical therapy, chiropractic manipulation, and provision of an educational booklet for the treatment of patients with low back pain. New England Journal of Medicine 1998 Oct 8;339(15):1021-9.
(7) Hurwitz E.L., Morgenstern H., Harber P., Kominski G.F., Belin T.R., Yu F., et al. A randomized trial of medical care with and without physical therapy and chiropractic care with and without physical modalities for patients with low back pain: 6-month follow-up outcomes from the UCLA low back pain study. Spine 2002 Oct 15;27(20):2193-204.