Stroke – Pathophysiology
Stroke is caused by a blocked blood vessel or bleeding in the brain. The signs of a stroke include a sudden severe headache, weakness, numbness, vision problems, confusion, trouble walking or talking, dizziness and slurred speech.
A stroke occurs when the blood supply to part of your brain is interrupted or severely reduced, depriving brain tissue of oxygen and nutrients. Within minutes, brain cells begin to die.
A stroke is a medical emergency. Prompt treatment is crucial. Early action can minimize brain damage and potential complications.
The good news is that strokes can be treated and prevented, and many fewer Americans die of stroke now than even 15 years ago.
Watch for these signs and symptoms if you think you or someone else may be having a stroke. Note when your signs and symptoms begin, because the length of time they have been present may guide your treatment decisions:
- Trouble with speaking and understanding. You may experience confusion. You may slur your words or have difficulty understanding speech.
- Paralysis or numbness of the face, arm or leg. You may develop sudden numbness, weakness or paralysis in your face, arm or leg, especially on one side of your body. Try to raise both your arms over your head at the same time. If one arm begins to fall, you may be having a stroke. Similarly, one side of your mouth may droop when you try to smile.
- Trouble with seeing in one or both eyes. You may suddenly have blurred or blackened vision in one or both eyes, or you may see double.
- Headache. A sudden, severe headache, which may be accompanied by vomiting, dizziness or altered consciousness, may indicate you’re having a stroke.
- Trouble with walking. You may stumble or experience sudden dizziness, loss of balance or loss of coordination.
When to see a doctor
Seek immediate medical attention if you notice any signs or symptoms of a stroke, even if they seem to fluctuate or disappear.
Think “FAST” and do the following:
- Face. Ask the person to smile. Does one side of the face droop?
- Arms. Ask the person to raise both arms. Does one arm drift downward? Or is one arm unable to raise up?
- Speech. Ask the person to repeat a simple phrase. Is his or her speech slurred or strange?
- Time. If you observe any of these signs, call 911 immediately.
Call 911 or your local emergency number right away. Don’t wait to see if symptoms go away. Every minute counts. The longer a stroke goes untreated, the greater the potential for brain damage and disability.
If you’re with someone you suspect is having a stroke, watch the person carefully while waiting for emergency assistance.
A stroke occurs when the blood supply to your brain is interrupted or reduced. This deprives your brain of oxygen and nutrients, which can cause your brain cells to die.
A stroke may be caused by a blocked artery (ischemic stroke) or the leaking or bursting of a blood vessel (hemorrhagic stroke). Some people may experience only a temporary disruption of blood flow to their brain (transient ischemic attack, or TIA).
About 85 percent of strokes are ischemic strokes. Ischemic strokes occur when the arteries to your brain become narrowed or blocked, causing severely reduced blood flow (ischemia). The most common ischemic strokes include:
- Thrombotic stroke. A thrombotic stroke occurs when a blood clot (thrombus) forms in one of the arteries that supply blood to your brain. A clot may be caused by fatty deposits (plaque) that build up in arteries and cause reduced blood flow (atherosclerosis) or other artery conditions.
- Embolic stroke. An embolic stroke occurs when a blood clot or other debris forms away from your brain — commonly in your heart — and is swept through your bloodstream to lodge in narrower brain arteries. This type of blood clot is called an embolus.
Hemorrhagic stroke occurs when a blood vessel in your brain leaks or ruptures. Brain hemorrhages can result from many conditions that affect your blood vessels, including uncontrolled high blood pressure (hypertension), overtreatment with anticoagulants and weak spots in your blood vessel walls (aneurysms).
A less common cause of hemorrhage is the rupture of an abnormal tangle of thin-walled blood vessels (arteriovenous malformation) present at birth. Types of hemorrhagic stroke include:
- Intracerebral hemorrhage. In an intracerebral hemorrhage, a blood vessel in the brain bursts and spills into the surrounding brain tissue, damaging brain cells. Brain cells beyond the leak are deprived of blood and also damaged.High blood pressure, trauma, vascular malformations, use of blood-thinning medications and other conditions may cause an intracerebral hemorrhage.
- Subarachnoid hemorrhage. In a subarachnoid hemorrhage, an artery on or near the surface of your brain bursts and spills into the space between the surface of your brain and your skull. This bleeding is often signaled by a sudden, severe headache.A subarachnoid hemorrhage is commonly caused by the bursting of a small sack-shaped or berry-shaped outpouching on an artery known as an aneurysm. After the hemorrhage, the blood vessels in your brain may widen and narrow erratically (vasospasm), causing brain cell damage by further limiting blood flow.
Transient ischemic attack (TIA)
A transient ischemic attack (TIA) — also known as a ministroke — is a brief period of symptoms similar to those you’d have in a stroke. A temporary decrease in blood supply to part of your brain causes TIAs, which often last less than five minutes.
Like an ischemic stroke, a TIA occurs when a clot or debris blocks blood flow to part of your brain. A TIA doesn’t leave lasting symptoms because the blockage is temporary.
Seek emergency care even if your symptoms seem to clear up. Having a TIA puts you at greater risk of having a full-blown stroke, causing permanent damage later. If you’ve had a TIA, it means there’s likely a partially blocked or narrowed artery leading to your brain or a clot source in the heart.
It’s not possible to tell if you’re having a stroke or a TIA based only on your symptoms. Up to half of people whose symptoms appear to go away actually have had a stroke causing brain damage.
Many factors can increase your risk of a stroke. Some factors can also increase your chances of having a heart attack. Potentially treatable stroke risk factors include:
Lifestyle risk factors
- Being overweight or obese
- Physical inactivity
- Heavy or binge drinking
- Use of illicit drugs such as cocaine and methamphetamines
Medical risk factors
- High blood pressure — the risk of stroke begins to increase at blood pressure readings higher than 120/80 millimeters of mercury (mm Hg). Your doctor will help you decide on a target blood pressure based on your age, whether you have diabetes and other factors.
- Cigarette smoking or exposure to secondhand smoke.
- High cholesterol.
- Obstructive sleep apnea — a sleep disorder in which the oxygen level intermittently drops during the night.
- Cardiovascular disease, including heart failure, heart defects, heart infection or abnormal heart rhythm.
Other factors associated with a higher risk of stroke include:
- Personal or family history of stroke, heart attack or transient ischemic attack.
- Being age 55 or older.
- Race — African-Americans have a higher risk of stroke than do people of other races.
- Gender — Men have a higher risk of stroke than women. Women are usually older when they have strokes, and they’re more likely to die of strokes than are men. Also, they may have some risk from some birth control pills or hormone therapies that include estrogen, as well as from pregnancy and childbirth.
A stroke can sometimes cause temporary or permanent disabilities, depending on how long the brain lacks blood flow and which part was affected. Complications may include:
- Paralysis or loss of muscle movement. You may become paralyzed on one side of your body, or lose control of certain muscles, such as those on one side of your face or one arm. Physical therapy may help you return to activities hampered by paralysis, such as walking, eating and dressing.
- Difficulty talking or swallowing. A stroke may cause you to have less control over the way the muscles in your mouth and throat move, making it difficult for you to talk clearly (dysarthria), swallow or eat (dysphagia). You also may have difficulty with language (aphasia), including speaking or understanding speech, reading or writing. Therapy with a speech and language pathologist may help.
- Memory loss or thinking difficulties. Many people who have had strokes experience some memory loss. Others may have difficulty thinking, making judgments, reasoning and understanding concepts.
- Emotional problems. People who have had strokes may have more difficulty controlling their emotions, or they may develop depression.
- Pain. People who have had strokes may have pain, numbness or other strange sensations in parts of their bodies affected by stroke. For example, if a stroke causes you to lose feeling in your left arm, you may develop an uncomfortable tingling sensation in that arm.People also may be sensitive to temperature changes, especially extreme cold after a stroke. This complication is known as central stroke pain or central pain syndrome. This condition generally develops several weeks after a stroke, and it may improve over time. But because the pain is caused by a problem in your brain, rather than a physical injury, there are few treatments.
- Changes in behavior and self-care ability. People who have had strokes may become more withdrawn and less social or more impulsive. They may need help with grooming and daily chores.
As with any brain injury, the success of treating these complications will vary from person to person.
If you’re experiencing stroke symptoms, getting to a highly specialized treatment center that can quickly diagnose and deliver individualized treatment can have a dramatic impact on your outcome.
At Mayo Clinic, the nation’s leading neurosciences team of emergency stroke experts will quickly evaluate the type of stroke you’re having and the areas of your brain affected by the stroke. They also need to rule out other possible causes of your symptoms, such as a brain tumor or a drug reaction. Your care team will likely use several tests to immediately determine your risk of stroke, including:
- Examination. Your doctor will ask you or a family member what symptoms you’ve been having, when they started and what you were doing when they began. Your doctor then will evaluate whether these symptoms are still present.Your doctor will want to know what medications you take and whether you have experienced any head injuries. You or your family member may be asked about your personal and family history of heart disease, transient ischemic attack or stroke.
Your doctor will perform a detailed neurological and medical examination. This includes checking your blood pressure and using a stethoscope to listen to your heart and to listen for a whooshing sound (bruit) over your neck, which may indicate hardening or narrowing (atherosclerosis) of the carotid arteries. Your doctor may also use an ophthalmoscope to check for signs of tiny cholesterol crystals or clots in the blood vessels at the back of your eyes.
- Blood tests. You may have several blood tests, which tell your care team how fast your blood clots, whether your blood sugar is abnormally high or low, whether critical blood chemicals are out of balance, or whether you may have an infection. Care providers will manage your blood’s clotting time and levels of sugar and key chemicals as part of your stroke care.
- Computerized tomography (CT) scan. A CT scan uses a series of X-rays to create a detailed image of your brain. A CT scan can show bleeding (hemorrhage), tumors, strokes and other conditions. Doctors may inject a dye into your bloodstream to view your blood vessels in your neck and brain in greater detail (computerized tomography angiography).
- Magnetic resonance imaging (MRI). An MRI uses powerful radio waves and magnets to create a detailed view of your brain. An MRI can detect brain tissue damaged by an ischemic stroke and brain hemorrhages. Your doctor may inject a dye into a blood vessel to view the arteries and veins and highlight blood flow (magnetic resonance angiography, or magnetic resonance venography).
- Carotid ultrasound. In this test, sound waves create detailed images of the inside of the carotid arteries in your neck. This test shows buildup of fatty deposits (plaques) and blood flow in your carotid arteries.
- Cerebral angiogram. For this test, your doctor inserts a thin, flexible tube (catheter) through a small incision, usually in your groin, and guides it through your major arteries and into your carotid or vertebral artery. Then your doctor injects a dye into your blood vessels to make them visible under X-ray imaging. This procedure gives a detailed view of arteries in your brain and neck.
- Echocardiogram. An echocardiogram uses sound waves to create detailed images of your heart. An echocardiogram can find a source of clots in your heart that may have traveled from your heart to your brain and caused your stroke.You may have a transesophageal echocardiogram. In this test, your doctor inserts a flexible tube with a small device (transducer) attached into your throat and down into the tube that connects the back of your mouth to your stomach (esophagus). Because your esophagus is directly behind your heart, a transesophageal echocardiogram can create clear, detailed ultrasound images of your heart and any blood clots.
Mayo Clinic subspecialized experts conduct these tests and immediately collaborate with each other to provide accurate diagnoses and timely treatment strategies individualized for each patient.
Emergency treatment for stroke depends on whether you’re having an ischemic stroke blocking an artery — the most common kind — or a hemorrhagic stroke that involves bleeding into the brain.
To treat an ischemic stroke, doctors must quickly restore blood flow to your brain.
Emergency treatment with medications. Therapy with clot-busting drugs must start within 3 hours if they are given into the vein — and the sooner, the better. Quick treatment not only improves your chances of survival but also may reduce complications. You may be given:
- Aspirin. Aspirin is an immediate treatment given in the emergency room to reduce the likelihood of having another stroke. Aspirin prevents blood clots from forming.
- Intravenous injection of tissue plasminogen activator (TPA). Some people can benefit from an injection of a recombinant tissue plasminogen activator (TPA), also called alteplase. An injection of TPA is usually given through a vein in the arm. This potent clotbusting drug needs to be given within 4.5 hours after stroke symptoms begin if it’s given in the vein.TPA restores blood flow by dissolving the blood clot causing your stroke, and it may help people who have had strokes recover more fully. Your doctor will consider certain risks, such as potential bleeding in the brain, to determine if TPA is appropriate for you.
Emergency procedures. Doctors sometimes treat ischemic strokes with procedures that must be performed as soon as possible, depending on features of the blood clot:
- Medications delivered directly to the brain. Doctors may insert a long, thin tube (catheter) through an artery in your groin and thread it to your brain to deliver TPA directly into the area where the stroke is occurring. The time window for this treatment is somewhat longer than for intravenous TPA but is still limited.
- Mechanical clot removal. Doctors may use a catheter to maneuver a tiny device into your brain to physically break up or grab and remove the clot.
However, recent studies suggest that for most people, delivering medication directly to the brain (intra-arterial thrombolysis) or using a device to break up or remove clots (mechanical thrombectomy) may not be beneficial. Researchers are working to determine who might benefit from this procedure.
Other procedures. To decrease your risk of having another stroke or transient ischemic attack, your doctor may recommend a procedure to open up an artery that’s narrowed by fatty deposits (plaques). Doctors sometimes recommend the following procedures to prevent a stroke. Options will vary depending on your situation:
- Carotid endarterectomy. In a carotid endarterectomy, a surgeon removes plaques from arteries that run along each side of your neck to your brain (carotid arteries). In this procedure, your surgeon makes an incision along the front of your neck, opens your carotid artery and removes plaques that block the carotid artery.Your surgeon then repairs the artery with stitches or a patch made from a vein or artificial material (graft). The procedure may reduce your risk of ischemic stroke. However, a carotid endarterectomy also involves risks, especially for people with heart disease or other medical conditions.
- Angioplasty and stents. In an angioplasty, a surgeon gains access to your carotid arteries most often through an artery in your groin. Here, he or she can gently and safely navigate to the carotid arteries in your neck. A balloon is then used to expand the narrowed artery. Then a stent can be inserted to support the opened artery.
Emergency treatment of hemorrhagic stroke focuses on controlling your bleeding and reducing pressure in your brain. Surgery also may be performed to help reduce future risk.
Emergency measures. If you take warfarin (Coumadin) or anti-platelet drugs such as clopidogrel (Plavix) to prevent blood clots, you may be given drugs or transfusions of blood products to counteract the blood thinners’ effects. You may also be given drugs to lower pressure in your brain (intracranial pressure), lower your blood pressure, prevent vasospasm or prevent seizures.
Once the bleeding in your brain stops, treatment usually involves supportive medical care while your body absorbs the blood. Healing is similar to what happens while a bad bruise goes away. If the area of bleeding is large, your doctor may perform surgery to remove the blood and relieve pressure on your brain.
Surgical blood vessel repair. Surgery may be used to repair blood vessel abnormalities associated with hemorrhagic strokes. Your doctor may recommend one of these procedures after a stroke or if an aneurysm or arteriovenous malformation (AVM) or other type of vascular malformation caused your hemorrhagic stroke:
- Surgical clipping. A surgeon places a tiny clamp at the base of the aneurysm, to stop blood flow to it. This clamp can keep the aneurysm from bursting, or it can prevent rebleeding of an aneurysm that has recently hemorrhaged.
- Coiling (endovascular embolization). In this procedure, a surgeon inserts a catheter into an artery in your groin and guides it to your brain using X-ray imaging. Your surgeon then guides tiny detachable coils into the aneurysm (aneurysm coiling). The coils fill the aneurysm, which blocks blood flow into the aneurysm and causes the blood to clot.
- Surgical AVM removal. Surgeons may remove a smaller AVM if it’s located in an accessible area of your brain, to eliminate the risk of rupture and lower the risk of hemorrhagic stroke. However, it’s not always possible to remove an AVM if its removal would cause too large a reduction in brain function, or if it’s large or located deep within your brain.
- Intracranial bypass. In some unique circumstances, surgical bypass of intracranial blood vessels may be an option to treat poor blood flow to a region of the brain or complex vascular lesions, such as aneurysm repair.
- Stereotactic radiosurgery. Using multiple beams of highly focused radiation, stereotactic radiosurgery is an advanced minimally invasive treatment used to repair vascular malformations.
Stroke recovery and rehabilitation
Following emergency treatment, stroke care focuses on helping you regain your strength, recover as much function as possible and return to independent living. The impact of your stroke depends on the area of the brain involved and the amount of tissue damaged.
If your stroke affected the right side of your brain, your movement and sensation on the left side of your body may be affected. If your stroke damaged the brain tissue on the left side of your brain, your movement and sensation on the right side of your body may be affected. Brain damage to the left side of your brain may cause speech and language disorders.
In addition, if you’ve had a stroke, you may have problems with breathing, swallowing, balancing and vision.
Most stroke survivors receive treatment in a rehabilitation program. Your doctor will recommend the most rigorous therapy program you can handle based on your age, overall health and your degree of disability from your stroke. Your doctor will take into consideration your lifestyle, interests and priorities, and the availability of family members or other caregivers.
Your rehabilitation program may begin before you leave the hospital. It may continue in a rehabilitation unit of the same hospital, another rehabilitation unit or skilled nursing facility, an outpatient unit, or your home.
Every person’s stroke recovery is different. Depending on your condition, your treatment team may include:
- Doctor trained in brain conditions (neurologist)
- Rehabilitation doctor (physiatrist)
- Physical therapist
- Occupational therapist
- Recreational therapist
- Speech therapist
- Social worker
- Case manager
- Psychologist or psychiatrist
Video Credit: Nucleus Medical Media