Uncommon Causes of Stroke
Whether due to a clot or a bleed there are many causes of stroke. Some are less common than others.
Stroke is actually three different disorders — ischemic stroke,caused by a blockage of an artery in the brain or leading to it,resulting in lack of blood flow;intracerebral hemorrhage, the rupture of an artery inside the brain;and subarachnoid hemorrhage, the rupture of an artery in the areas around the surface of the brain.Each of these,in turn,has several causes.
Dr. Scott Kasner
Over the 20 years of publishing Stroke Connection, we have heard of many of those causes.Most strokes result from a handful of causes. However,this article will focus on three causes considered uncommon,but that we’ve heard of most often — carotid/vertebral dissection, arteriovenous malformation and cavernous angioma.We talked to neurologist Scott Kasner,professor of neurology at the Perelman School of Medicine,University of Pennsylvania, about this subject.
There are two carotid arteries in the front of the neck and two vertebral arteries in the back, and they transport all the blood that feeds the brain. The carotid and vertebral arteries have three layers: a thin inner lining; a middle layer which is the thickest and consists of smooth muscle; and the outer layer, made of connective tissue.
A dissection in these arteries occurs when the inner lining tears and detaches from the artery. It’s not a tear that goes all the way through the vessel and leaks blood. As with any cut, the body generates clotting factors to stop the tear from spreading. “It’s like a piece of loose wall or shelf paper that is sticky and allows a clump of dust to form underneath it,” Dr. Kasner said. “But when the tear happens in an artery, that clump is a clot (thrombus) that can block off the entire artery, or a piece of the clot can break off and travel up to the brain. Either of those can cause an ischemic stroke.”
Dissections result from a wide variety of causes, and are usually very different from the more typical buildup of plaque in the arteries (atherosclerosis). Dissections are sometimes the result of an injury, like whiplash from a car accident or blunt force trauma from sports injuries. Dissections have also been reported from holding the head in an odd position, like when someone holds a cell phone between the ear and shoulder, or turning the head while backing up a car, or even sneezing hard. Dissections have been reported in persons after chiropractic manipulation of the neck. In addition, certain medical conditions such as Marfan syndrome, a genetic disease of the connective tissue, and fibromuscular dysplasia (FMD), a blood vessel disease where the middle of the artery wall grows abnormally and deforms the artery, can also cause dissection. In these patients dissection is called “spontaneous,” meaning that it occurs without trauma to the head or neck.Symptoms
Stroke is not usually the first sign of a dissection. More often, symptoms develop over a few hours or even days, even in those people who have traumatic injuries. Those initial symptoms include headache or neck pain, often radiating behind the eye because the carotid arteries run behind the eyes. Another symptom is pulsatile tinnitus, a pulsating, whooshing sound in the head, which is actually the blood flowing through the vessels. “Occasionally, people will have a drooping eyelid and a smaller pupil on that side,” Dr. Kasner said. (This is called Horner’s syndrome.) Other symptoms include trouble swallowing or a decrease in the sense of taste.
Carotid dissection is typically diagnosed using an MRA (magnetic resonance angiography) or CTA (computed tomography angiography) scan. “Carotid ultrasound is less sensitive. An invasive catheter angiogram is arguably the best test but is not usually necessary because most of the time you can see it by MRA or CTA,” Dr. Kasner said.
Dr. Kasner indicated that some unexplained strokes may, in fact, be carotid dissections. Patients who have stroke symptoms may get a carotid ultrasound and an electrocardiogram (EKG), neither of which can detect a dissection, so they may be told no cause was found. “Occasionally I see patients who tell me, ‘I had a really bad cold. I was sneezing my brains out, and then I had this pain in my neck and eye. My eyelid was drooping. And two days later, I had a stroke, and they didn’t figure out the cause. They told me everything looked normal. Now it’s two months later, time enough for the tear to heal, and my guess is that that was probably carotid dissection, but because the right test wasn’t done at the right time, it was missed. So dissections probably are misdiagnosed in some patients.”
Genes, Environment or Other Causes?
In addition to Marfan syndrome and FMD, there is some evidence that people with an inherited collagen abnormality called Ehlers-Danlos syndrome may be prone to dissection. “There probably is a familial genetic component, but in big part dissection is environmental, typically related to some trauma,” Dr. Krasner said. “However, we all hold our cell phones in a funny way, or turn our heads when we back up our cars, and most of us don’t get dissections. So there may be some underlying weakness of the arterial wall that we don’t know about.”
“That said, the most common ‘cause’ of dissection is ‘spontaneous,’ meaning without major trauma, but often with a predisposing factor like sudden neck turn or heavy lifting,” Dr. Kasner said. “That list includes weird stuff like sneezing, coughing, rocking a baby, holding a cell phone with the shoulder, riding a roller coaster, etc.”
Treatment and Recurrence
Survivors of a carotid dissection are usually treated with clot-prevention therapy, such as aspirin or anticoagulants. However, there is a very low risk of recurrent stroke once the tear has healed. If patients have recurrent strokes despite medical therapy, then they might be treated with stents. “The highest risk (of recurrent stroke) is actually in the first couple of days after the stroke, and then it declines substantially,” Dr. Kasner said.
Of all the uncommon causes of ischemic stroke, Dr. Kasner estimated that dissection is the most common. “If all of the uncommon causes together are about five percent of all strokes, dissection is probably a quarter of those,” he said.
ARTERIOVENOUS MALFORMATION (AVM)
An AVM is a tangle of blood vessels in the brain or on its surface that diverts blood directly from the arteries to the veins, bypassing normal brain tissue. Because the arterial blood is under high pressure, and the walls of veins are not made to withstand arterial blood pressure, there is a danger that the veins will rupture or leak and cause a hemorrhagic stroke. About half of AVM patients have an intracerebral hemorrhage. “However, when AVMs rupture they may bleed both into the brain itself as well as into the subarachnoid space around the brain,” Dr. Kasner said. “So those patients have intracerebral hemorrhages as well as subarachnoid hemorrhages.”
Typically AVMs cause no symptoms before they rupture or leak, although some people have seizures before or instead of having hemorrhages. Increased blood flow around the AVM may also cause headaches. However, unless they have a stroke, people with AVMs may never know they have one. It’s estimated that about one in 200–500 people may have an AVM, and they are more common in men. The age range for a problem to arise is typically 15 to 40.
About 10 to 15 percent of AVM bleeds result in death. The chance of permanent brain injury is 20 to 30 percent. Unless they are removed or closed off, there is always a risk that they will bleed, and each time blood leaks into the brain, normal brain tissue is damaged. This results in loss of normal function, which may be temporary or permanent.
AVMs are diagnosed through some form of angiography (blood vessel imaging), though large ones are visible with MRI or CT scans. “In general, they are hard to diagnose in any kind of preemptive fashion just because they don’t have symptoms,” Dr. Kasner said. In other words, it’s unlikely that a person would go to the doctor and ask to be checked for AVM.
Genes, Environment or Other Causes?
Although they are present at birth, AVMs don’t seem to be inherited. “There’s some developmental component, which may in part be environmental,” Dr. Kasner said.
Treatment and Recurrence
There are several treatment options depending on the AVM’s size and location. AVMs do need to be removed or neutralized. As long as they remain there is danger they will hemorrhage.
- Surgery. If an AVM has bled or is in an area that can be easily operated on, surgical removal is a good option. When the AVM is completely taken out, the possibility of any further bleeding should be eliminated. Depending on the complexity of the tangle of blood vessels, the surgery may be very intricate. “This is a cluster of abnormal blood vessels, and unless you get a 100 percent of it, people can essentially recruit new blood vessels to connect to it,” Dr. Kasner said. “That means the AVM can come back if not completely eliminated, so patients need to be monitored closely even after treatment.”
- Stereotactic radiosurgery. An AVM in an area that’s difficult to reach by regular surgery may be treated with stereotactic radiosurgery, which is a form of radiation therapy that focuses high-power energy on the cluster of blood vessels to damage them. Despite its name, it is a treatment, not a surgical procedure, so no incisions are made. The goal is to make a scar that will cause the AVM to “clot off” so blood no longer flows through it.
- Interventional neuroradiology/endovascular neurosurgery. Another option is to treat part or all of the AVM by inserting a catheter inside the arteries that supply blood to it. Then the abnormal vessels are blocked off with various materials such as special glues, micro coils and other materials used to stop blood flowing to the AVM.
“If they’re successfully treated, the risk of recurrence should be fairly low, but it’s sometimes hard to treat them completely,” Dr. Kasner said. If untreated, the chance of an AVM bleeding is 1 to 3 percent per year, which means over 15 years, the total chance of an AVM bleeding into the brain is 25 percent. Because of this increasing risk, it is unwise to leave an AVM alone once it has bled.
CAVERNOUS ANGIOMA (CA)
A cavernous angioma is a cluster of small, abnormally formed blood vessels in the brain that are enlarged and irregular in structure. These blood vessels have very thin walls and lack the elastic fibers present in larger vessels. As a result, these blood vessels are prone to leakage, which can cause hemorrhagic strokes. “They can present in a similar fashion to AVMs with headache and hemorrhagic stroke, but they tend to be smaller and more localized and are generally much less dangerous than AVMs,” Dr. Kasner said. CA may occur in the brain, brain stem or spinal cord.
Typically they don’t bleed into the space between the brain and skull. Bleeding may cause any stroke symptom, including weakness, numbness or double vision. Other symptoms may include headaches, seizures, and hearing or vision loss. They rarely cause a large, life-threatening hemorrhage. About a quarter of people with CA never have any symptoms related to them.
They are diagnosed by MRI, where the collection of vessels, which are described as looking like a mulberry or a piece of popcorn, is typically surrounded by a dark ring of old blood from previous leaks. CA lesions are not visible on typical angiograms. The location and number of mulberry-looking lesions determine the severity of this disorder. The malformations can change in size and number over time.
Genes, Environment or Other Causes?
There are two forms of CA — familial and sporadic. The familial form is passed from parent to child, and people with this form typically have multiple lesions. Those with the sporadic form have no family history of the disorder and usually have only one malformation. In the familial form, an affected person inherits the mutation from one affected parent. Most people with CA have the sporadic form.
Treatment and Recurrence
Surgery to remove the lesion is the preferred treatment for CAs that are leaking and accessible. Surgical removal eliminates the risk of future bleeding. Because CAs are not visible on an angiogram, any type of surgery using catheters is not possible. At this time, it is not known whether stereotactic radiosurgery (described above as a treatment for AVM) may be helpful in treating some deep or inaccessible lesions. For more information about cavernous angiomas, contact the Angioma Alliance, angiomaalliance.org or 866-432-5226.
Considering that our brains contain 100,000 miles of blood vessels, which carry 20-25 percent of the blood in our bodies, it is not too surprising that there are multiple ways people can have strokes. Perhaps the best any of us can do is make prevention a habit, whether or not we have the genes, gender or race that increases risk. Here are tips for lowering your risk of stroke:
- Control your blood pressure because there are no good outcomes from high blood pressure.
- If you smoke, stop — it doesn’t do one good thing for you … and many bad things.
- If you have diabetes, treat it. If you don’t know whether you have it, find out because diabetes increases your risk of stroke and heart disease.
- Find out if you have a heart rhythm disorder — it is a leading cause of stroke.
- Every human body has some level of atherosclerosis (even babies!) so have your cholesterol checked and control it if needed.
- Reduce your stress. Every day do something you enjoy.
- Commit to eating better — less sodium, less added sugar, less fat, fewer calories, more fruits and vegetables.
- Get active — 150 minutes of moderate intensity aerobic activity per week is recommended, but whatever your body allows you to do, do it — some physical activity is always better than none.
- Maintain a healthy weight.
See a comprehensive list of uncommon causes of stroke and an update on fibromuscular dysplasia.
ISCHEMIC STROKE accounts for about 80 percent of all strokes. The most common causes of ischemic stroke are heart problems such as atrial fibrillation and hardening of the arteries (atherosclerosis), where clots form in the heart or arteries and then block blood flow to the brain. “A third important cause is small vessel disease, which occurs when the microscopic blood vessels of the brain narrow and close off, typically because of high blood pressure,” Dr. Kasner said. “Those three account for the majority of the known causes of ischemic stroke.”
The primary cause of bleeding strokes is chronic damage to blood vessels from high blood pressure that causes them to rupture. In older patients, typically over 70, another major cause is cerebral amyloid angiopathy. “In this condition the blood vessels walls have deposits of an amyloid protein that makes them brittle and prone to bleeding, even without high blood pressure,” Dr. Kasner said. High blood pressure increases the risk of stroke — 77 percent of Americans treated for a first stroke have blood pressure over 140/90.
Those causes account for approximately three-quarters of all strokes. Of the remainder, most are categorized as “cryptogenic strokes.” This means the patient had a stroke, but the cause was never determined. Sometimes this is the result of the patient receiving a limited evaluation, possibly because the hospital lacked the proper equipment. Other times, a thorough examination doesn’t give doctors enough information to determine the cause.
“Five percent of all strokes are due to the ‘other determined causes,’” Dr. Kasner said. “In younger stroke patients, the ‘other determined causes’ account for about 25 percent of all strokes.”
This information is provided as a resource to our readers. These tips, products or resources have not been reviewed or endorsed by the American Stroke Association.