What is a Stroke?
The brain demands a constant supply of blood, which carries the oxygen and nutrients it needs to function. Blood enters the brain through two sets of arteries, the carotid arteries and the vertebral arteries.
- The carotid arteries are located in the front of your neck and are what you feel when you take your pulse just under your jaw. The carotid arteries split into the external and internal arteries near the top of your neck with the external carotid arteries supplying the blood to your face and the internal carotid arteries going into the skull. Inside the skull, the internal carotid arteries branch into two large arteries – the anterior cerebral and middle cerebral arteries, and several smaller arteries – the ophthalmic, posterior communicating, and anterior choroidal arteries. These arteries supply blood to the front two-thirds of your brain.
- The vertebral arteries extend alongside your spinal column and cannot be felt from the outside. The vertebral arteries join to form a single basilar artery near the brain stem, which is located near the base of your skull. The vertebrobasilar system sends many small branches into the brain stem and branches off to form the posterior cerebellar and posterior meningeal arteries, which supply the back third of your brain. The jugular and other veins carry blood out of the brain.
Because the brain relies on only two sets of major arteries for its blood supply, it is very important that these arteries are healthy and functioning correctly. A stroke occurs when there is an interruption of the blood supply to any part of the brain. Restrictions in blood flow may occur from vessel narrowing (stenosis), clot formation (thrombosis), blockage (embolism), or blood vessel rupture (hemorrhage). As a result, part of the brain is deprived of the blood it needs, so it starts to die, and the abilities controlled by that area of the brain are lost. Lack of sufficient blood flow (ischemia) affects brain tissue and may cause a stroke.
Regardless of the underlying cause and condition, it is crucial that proper blood flow and oxygen be restored to the brain as quickly as possible. Without oxygen and important nutrients, the affected brain cells are either damaged or die within a few minutes. Once brain cells die, they cannot regenerate, and devastating damage may occur, sometimes resulting in physical, cognitive and mental disabilities.
This commonly used term, stroke, can refer to more than one nervous system disease. Other names for stroke are cerebrovascular disease; CVA; cerebral infarction and cerebral hemorrhage. However, the most common meaning of the term is to refer to cerebral infarction, due to cerebral ischemia.
Types of Stroke
There are two types of stroke: Ischemic and hemorrhagic strokes. The interruption of blood flow can be caused by a blockage, leading to the more common ischemic stroke, or by the breakage or rupture of a blood vessel in the brain, leading to the more deadly hemorrhagic stroke.
What is an ischemic stroke?
Ischemic stroke is the most common type of stroke, accounting for about 87% of all strokes. Ischemic strokes occur as a result of a disease of the arteries, known as atherosclerosis. This is a condition where fatty material, known as plaque, builds up within the inner lining of the artery, causing them to narrow and become less flexible. Platelets and other blood products can stick to this, as part of a clot. The narrowing, also referred to as stenosis, reduces the amount of blood and oxygen that is being delivered to all surfaces of the brain. These fatty deposits can cause two types of obstruction:
- Cerebral thrombosis refers to a thrombus (blood clot) that develops at the clogged part of the vessel, blocking an artery to the brain and stopping blood flow.
- Cerebral embolism occurs when a piece of plaque or thrombus travels from its original site and blocks an artery downstream. The material that has moved is called an embolus. How much of the brain is damaged or affected depends on exactly how far downstream in the artery the blockage occurs. A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation. It creates conditions where clots can form in the heart, dislodge and travel to the brain.
- Arteries can sometimes tear or split into layers with bleeding in-between each layer due to trauma, simple manipulation of the neck, or spontaneous occurrence. Known as dissection, this process can block blood flow to the brain, lead to the formation of blood clots, and eventually result in a stroke. Dissections are often the main cause of stroke in individuals under 40 years of age.
In most cases, the carotid or vertebral arteries do not become completely blocked and a small stream of blood continues to trickle to the brain. The reduced blood flow to the brain starves the cells of nutrients and quickly leads to a malfunctioning of the cells. As a part of the brain stops functioning, symptoms of a stroke occur.
What is a Hemorrhagic Stroke?
A hemorrhagic stroke is caused by the rupture of a blood vessel with bleeding into the tissue of the brain. Hemorrhage can either occur on its own from blood vessel disease, or along with a cerebral infarction.
- Subarachnoid Hemorrhage: A subarachnoid hemorrhage has many possible causes but is most commonly the result of a cerebral aneurysm that ruptures in the space between the surface of the brain and the skull, causing blood to pour into the area around the outside of the brain. This typically leads to increased pressure in the brain, injuring brain cells, and is one of the most common forms of brain hemorrhage.
- Intracerebral Hemorrhage: Intracerebral hemorrhage is caused when an artery bursts and bleeds within the brain tissue, causing brain cells to die and leading to the sudden onset of neurological symptoms. Many intracerebral hemorrhages are due to changes in the arteries caused by long-term high blood pressure, or hypertension. Hypertensive hemorrhage is the most common cause of hemorrhagic stroke.
- Other Sudden Hemorrhage: Other sources of sudden hemorrhage into the brain include arteriovenous malformation, arteriovenous fistulas, cavernous malformation and Moyamoya disease.
The treatment for hemorrhagic stroke depends upon the cause of the bleeding. Following hemorrhage, patients are closely monitored in our neurointensive care unit where the physician comes up with a treatment plan specifically to that patient’s cause of bleeding, blood pressure levels, medical history, and existing medical conditions. Please see specific document pertaining to the patient’s source of hemorrhage for more information on treatment and what to expect.
What is a TIA?
A transient ischemic attack (TIA), or “mini-stroke,” is similar to an ischemic stroke in that it is caused by a blocked artery, causing stroke-like symptoms, but the blockage dislodges before any permanent damage occurs. The symptoms clear up completely, and resolve so quickly that oftentimes patients ignore the situation entirely, especially when symptoms only last a few seconds to a few minutes. The downside of this is that a TIA may precede a stroke by days or weeks and represent a warning sign that should not be overlooked. In fact, about 30% of all people who suffer a major stroke experience a prior TIA, and 10% of all TIA victims suffer a stroke within two weeks. The most common symptoms include sudden numbness or weakness in the face, arm or leg, especially on one side of the body, sudden confusion or trouble speaking, sudden trouble seeing in one or both eyes, loss of balance or coordination, and sudden extreme headache. Patients experiencing TIA symptoms should undergo a comprehensive evaluation quickly because early intervention is essential in effectively preventing a major stroke. If you experience TIA symptoms, seek emergency medical help and notify your primary care physician immediately. Treatment options for TIA patients focus on treating carotid artery disease or cardiac problems.
Stroke in Young Adults
Up to 10% of strokes may occur in individuals under 45 years of age. These cases represent a challenge in terms of diagnosis and treatment. Patients typically undergo a detailed evaluation including brain imaging, vascular studies, cardiac evaluations and hematologic assessment using the most advanced diagnostic techniques. There are a variety of uncommon conditions which may occur in young adults, such as arterial dissection, vasculitis, cerebral vein thrombosis and moya-moya syndrome. Once the condition has been diagnosed, our team is able to come up with the most appropriate course of therapy.
The range and severity of early stroke symptoms vary considerably, but they share the common characteristic of being sudden. Warning signs may include some or all of the following symptoms:
- Dizziness, nausea, or vomiting
- Unusually severe headache
- Confusion, disorientation or memory loss
- Numbness, weakness in an arm, leg or the face, especially on one side of the body
- Abnormal or slurred speech
- Difficulty with comprehension
- Loss of vision or difficulty seeing
- Loss of balance, coordination, or the ability to walk
- It is especially important to note that many strokes may cause an utterly painless loss of neurological function, leading to potential hesitation to call 911 or visit an emergency room.
NOTE: It is important to check the time so you’ll know when the first symptom appeared. This will help the doctor in making the correct treatment decisions.
Stroke Effects: The effects of a stroke depend primarily on the location of the obstruction and the extent of brain tissue affected. One side of the brain controls the opposite side of the body, so a stroke affecting the right side will result in neurological complications on the left side of the body.
- Paralysis on the left side of the body
- Vision problems
- Quick, inquisitive or purposeless behavior
- Memory loss
A stroke on the left side may result in the following:
- Paralysis on the right side of the body
- Speech/language problems
- Slow, cautious behavior
- Memory loss
Facts and Statistics about Stroke in the US
- Stroke is the third leading cause of death in the United States of people over age 40, behind diseases of the heart and cancer.
- Stroke takes the lives of more than 137,000 people annually.
- That’s about 1 of every 18 deaths.
- On average, every 4 minutes someone dies of stroke.
- Stroke can happen to anyone, at anytime, regardless of race, sex or age.
- Approximately 55,000 more women than men have a stroke each year
- Men’s stroke incidence rates are greater than women’s at younger ages, but not older ages.
- African Americans have almost twice the risk of first-ever stroke compared with whites.
- Of all strokes:
- 87% ischemic
- 10% intracerebral hemorrhage
- 3% subarachnoid hemorrhage
- Stroke caused by intracranial atherosclerosis represents 10% of all ischemic strokes.
- While the incidence has increased, there has been a steady decline in mortality rates since 2002.
- About 795,000 Americans each year suffer a new or recurrent stroke.
- That means, on average, a stroke occurs every 40 seconds.
- Of this number, about 610,000 of these are first attacks, and 185,000 are recurrent.
- About 25% of people who recover from their first stroke will have another stroke within five years.
- The prevalence of transient ischemic attacks increases with age. Of 1,707 TIA patients evaluated in the emergency department of a large health care plan, 180 patients (or 10%) developed a stroke within 90 days.
- Stroke is a leading cause of serious long-term disability, with an estimated 5.4 million stroke survivors currently alive today.
- Stroke is the leading cause of nursing home admission.
- In 2010, stroke cost was around $73.7 billion in both direct and indirect costs in the United States alone.
Stroke Risks and Prevention
Although stroke is more common in older adults, anyone can have a stroke. By learning the signs and symptoms of stroke and treating risk factors preventively, you can help avert the devastating results of this disease.
Non-Modifiable Risk Factors
- Age: 60 or older
- Race: African-Americans have a much higher risk of death from a stroke than Caucasians do, partly because they are more prone to having high blood pressure, diabetes and obesity
- Having a family history of stroke
Modifiable Risk Factors
The best way to prevent a stroke is by reducing your stroke risk factors that are controllable. 80% of strokes are preventable.
Lifestyle Stroke Risk Factors
- Smoking: you can decrease your risk by quitting smoking. Your risk may be increased further if you take some forms of oral contraceptives and are a smoker. There is evidence that long-term secondhand smoke exposure may increase your risk of stroke.
- Physical inactivity and obesity: being inactive, obese, or both can increase your risk of high blood pressure, high blood cholesterol, diabetes, heart disease and stroke.
- Excessive consumption of Alcohol
- Drug abuse (heroin, cocaine, amphetamines)
Medical Stroke Risk Factors
- High blood pressure: Blood pressure of 140/90 mm Hg or higher is the number one risk factor for ischemic stroke. Controlling your blood pressure is crucial to stroke prevention.
- Carotid or other artery disease: The carotid and vertebral arteries in your neck supply blood to your brain. A carotid artery narrowed by fatty deposits from atherosclerosis (plaque buildups in artery walls) may become blocked by a blood clot. Narrowing of major arteries supplying the brain (carotid and vertebral) due to atherosclerosis
- High blood cholesterol: a high level of total cholesterol in the blood (240 mg/dL or higher) is a major risk factor for heart disease, which raises your risk of stroke.
- Having Diabetes: it is crucial to control your blood sugar levels, blood pressure and cholesterol levels.
- History of TIAs.
- Prior stroke or heart attack: if you have had a stroke, you are at a much higher risk of having another one. If you have had a heart attack, you are also at a much higher risk of having a stroke.
- People receiving hormone replacement therapy (HRT) have an overall 29% increased risk of stroke (ischemic stroke, in particular).
- Atrial Fibrillation – abnormality of heart rhythm. In most cases, abnormalities or damage to the heart’s structure are the most common cause of atrial fibrillation.
While reducing your modifiable risk factors is extremely hard, the primary motivation for this change will be based on the awareness of the risks incurred if a radical lifestyle change is not made. A surgical procedure can only treat a critical situation and medical therapy will only partially correct a biochemical or organic abnormality. Neither treatment will prevent a progressive deterioration of your body if you do not focus on breaking old habits.
The majority of cerebrovascular problems can be identified through diagnostic imaging tests. These tests allow physicians to examine how the brain looks, works and gets its blood supply. They also outline the injured brain area. Most of the tests are safe and painless. The three main categories of testing include imaging tests, electrical tests and blood flow tests.
MRI (magnetic resonance imaging) produces images of body structures using magnetic fields and computer technology. These images clearly show various types of nerve tissue and clear pictures of the brain stem and posterior brain. MRI of the brain can also help to determine whether there are signs of prior mini-strokes (TIA’s). MRI shows the location and extent of brain injury in the same way that a CT would, however, the image produced by MRI is sharper and more detailed than a CT. This is what makes MRI the scan of choice when diagnosing small, deep injuries.
MRA (magnetic resonance angiogram) is a noninvasive study also conducted in a magnetic resonance imager. The only difference is that this study provides an image of the arteries in your head and neck and can help detect blockage and aneurysms.
NOVA software is a flow analysis system that works with MRA to produce a 3D model of the vasculature, allowing the anatomy to be viewed from all angles. NOVA is the first system to offer fast, accurate, and non invasive determination of volumetric flow rates, velocity, waveforms, and flow direction. MRI and MRA with NOVA sequencing are almost always ordered when patients are suspected of stroke. Together these tests allow the physician to diagnose the problem and come up with the best treatment option. These are both noninvasive tests, although some patients may experience claustrophobia in the imager. It is important to let the office know if you are claustrophobic when they call to schedule your scan.
Computed tomography (CT or CAT scan) is a diagnostic image created after a computer reads x-rays. In some cases, iodine solution is injected through a vein in order to highlight brain structures. Bone, blood, and brain tissue have very different densities that can easily be distinguished on a CT scan. A CT scan is a useful diagnostic test for hemorrhagic strokes because blood can easily be seen. However, damage from an ischemic stroke may not be revealed on a CT scan for several hours or days and the individual arteries in the brain cannot be seen. CTA (CT angiography) allows clinicians to see blood vessels of the head and neck.
EEG and Evoked response are two basic tests that are run in order to show the brain’s electrical activity. An Electroencephalogram (EEG) is a diagnostic test in which small metal discs (electrodes) are placed on a person’s scalp to pick up electrical impulses. These electrical signals are printed out as brain waves. An Evoked Response test measures how the brain handles different sensory information. Electrodes record electrical impulses related to hearing, body sensation or vision.
Blood flow tests show any problem that may cause changes in blood flow to the brain. Most blood flow tests use ultrasound technology. A probe is placed over the suspect artery, especially arteries in the neck (carotid) or at the base of the skull (vertebral), and the amount of blood flow is determined. Carotid duplex (carotid ultrasound) is a procedure where ultrasound is used to help detect plaque, blood clots, or other problems with blood flow in the carotid arteries. A water-soluble gel is placed on the skin where the transducer (a handheld device that directs the high-frequency sound waves to the arteries being tested) is then placed. The gel helps transmit the sound to your skin surface. The ultrasound is turned on and images of the carotid arteries and pulse wave forms are obtained. Doppler ultrasound is another test where the same gel and transducer is placed on the skin over the veins of the extremity being tested. There is a “swishing” sound on the Doppler if the venous system is normal. Both the superficial and deep venous systems are evaluated in this test. There are no known risks in either of these tests, and they are noninvasive and painless.
Diagnostic Cerebral Angiogram: Please see Diagnostic Cerebral Angiogram Document for complete information on this procedure.
Lumbar puncture (spinal tap) is an invasive diagnostic test that uses a needle to remove a sample of cerebrospinal fluid from the space surrounding the spinal cord. This test can be helpful in detecting bleeding caused by a cerebral hemorrhage.
Acute and Preventative Treatment for Ischemic Stroke
Acute interventions can reduce the severity of the brain damage if the patient is rushed to the hospital the moment a stroke occurs. Treatment involves reducing risk factors and identifying the source of the blockage. Once the specific cause of an ischemic stroke is found, the best treatment can be determined.
Ischemic stroke is treated by removing the obstruction and restoring blood flow to the brain. One treatment for ischemic stroke is tissue plasminogen activator (tPA). Intravenous tPA helps dissolve the occluding thrombus in acute stroke, but must be administered within a three-hour window from the onset of symptoms to work best. Even with optimal timing, this drug may not always be effective. Only 3-5% of those who suffer a stroke reach the hospital in time to be considered for this treatment. tPA carries a risk for increased intracranial hemorrhage and is not used for hemorrhagic stroke.
Thrombolytic medication can also be administered directly onto the occluding thrombus. This kind of treatment delivers thrombolytic medication using the same catheterization techniques used with mechanical devices, is more specific than IV tPA, and consequently may require significantly lesser dosages of medication. The time limit to implement this type of intervention is also significantly (double) longer than that for IV tPA. Generally, only Comprehensive Stroke Care Centers offer this type of treatment.
For patients beyond the three-hour time window, removal of the thrombus intrarterially using mechanical devices is another common option. The Merci Retriever is the first FDA-approved medical device to remove blood clots from the brain in patients experiencing an ischemic stroke. The catheter-based device was invented by the UCLA interventional neuroradiology team and is used in minimally invasive procedures at stroke centers that offer endovascular therapy. The procedure is performed in the Angiography suite. A small incision is made in the patient’s groin, where a catheter is then inserted. The physician uses the live X-ray guidance to maneuver the catheter to the arteries in the neck. At the neck, a small catheter inside the larger catheter is guided through the arteries until it reaches the brain clot. The Merci Retriever, a straight wire inside the small catheter, pokes out beyond the clot and automatically coils into a corkscrew shape. Once the wire is pulled back into the clot, the corkscrew spins and grabs the clot. A balloon then inflates in the neck artery, temporarily cutting off blood flow, so the device can pull the clot out of the brain safely. The clot is finally removed through the catheter with a syringe.
Penumbra is also a microcatheter-based system device. This device is navigated to the clot in the same way as the Merci Retriever; however the Penumbra device uses aspiration to suction out the clot. This device is most effective if used within 8 hours of symptom onset. For optimal results, many of these treatments are done in conjunction with one another.
Carotid endarterectomy is the surgical approach used to treat carotid stenosis and reduce the risk of a stroke. Please see Carotid Artery Disease for more information.
Neurointerventional treatment for stroke share the advantages of no incision made in the skull, and an anesthesia time that is often dramatically shorter than for craniotomy. For more information on angioplasty and stenting, please see the Neurointerventional Procedures document. Carotid endarterectomy or angioplasty and stenting of the cervical and intracranial vessels may help reduce recurrent stroke in some cases.
Recovery and rehabilitation are important aspects of stroke treatment. In some cases, undamaged areas of the brain may be able to perform functions that were lost when the stroke occurred. Rehabilitation includes physical therapy, speech therapy, and occupational therapy. This type of recovery is measured in months to years. Many of our patients are sent to Cottage Rehabilitation Institute upon discharge from the hospital.
- Physical therapy involves using exercise and other physical means (massage, heat) and may help patients regain the use of their arms and legs and prevent muscle stiffness in patients with permanent paralysis.
- Speech therapy may help patients regain the ability to speak.
- Occupational therapy may help patients regain independent function and relearn basic skills such as getting dressed, preparing a meal, and bathing.