 Introduction
More than 2,400 years ago the father of medicine, Hippocrates, recognized and
described stroke-the sudden onset of paralysis. Until recently, modern medicine
has had very little power over this disease, but the world of stroke medicine is
changing and new and better therapies are being developed every day. Today, some
people who have a stroke can walk away from the attack with no or few
disabilities if they are treated promptly. Doctors can finally offer stroke
patients and their families the one thing that until now has been so hard to
give: hope.
In ancient times stroke was called apoplexy,* a general term that physicians
applied to anyone suddenly struck down with paralysis. Because many conditions
can lead to sudden paralysis, the term apoplexy did not indicate a specific
diagnosis or cause. Physicians knew very little about the cause of stroke and
the only established therapy was to feed and care for the patient until the
attack ran its course.
The first person to investigate the pathological signs of apoplexy was Johann
Jacob Wepfer. Born in Schaffhausen, Switzerland, in 1620, Wepfer studied
medicine and was the first to identify postmortem signs of bleeding in the
brains of patients who died of apoplexy. From autopsy studies he gained
knowledge of the carotid and vertebral arteries that supply the brain with
blood. He also was the first person to suggest that apoplexy, in addition to
being caused by bleeding in the brain, could be caused by a blockage of one of
the main arteries supplying blood to the brain; thus stroke became known as a
cerebrovascular disease ("cerebro" refers to a part of the brain; "vascular"
refers to the blood vessels and arteries).
Medical science would eventually confirm Wepfer's hypotheses, but until very
recently doctors could offer little in the area of therapy. Over the last two
decades basic and clinical investigators, many of them sponsored and funded in
part by the National Institute of Neurological Disorders and Stroke (NINDS),
have learned a great deal about stroke. They have identified major risk factors
for the disease and have developed surgical techniques and drug treatments for
the prevention of stroke. But perhaps the most exciting new development in the
field of stroke research is the recent approval of a drug treatment that can
reverse the course of stroke if given during the first few hours after the onset
of symptoms.
Studies with animals have shown that brain injury occurs within minutes of a
stroke and can become irreversible within as little as an hour. In humans, brain
damage begins from the moment the stroke starts and often continues for days
afterward. Scientists now know that there is a very short window of opportunity
for treatment of the most common form of stroke. Because of these and other
advances in the field of cerebrovascular disease stroke patients now have a
chance for survival and recovery.
What is Stroke?
A stroke occurs when the blood supply to part of the brain is
suddenly interrupted or when a blood vessel in the brain bursts, spilling blood
into the spaces surrounding brain cells. In the same way that a person suffering
a loss of blood flow to the heart is said to be having a heart attack, a person
with a loss of blood flow to the brain or sudden bleeding in the brain can be
said to be having a "brain attack."
Brain cells die when they no longer receive oxygen and nutrients from the blood
or when they are damaged by sudden bleeding into or around the brain. Ischemia
is the term used to describe the loss of oxygen and nutrients for brain cells
when there is inadequate blood flow. Ischemia ultimately leads to infarction,
the death of brain cells which are eventually replaced by a fluid-filled cavity
(or infarct) in the injured brain.
When blood flow to the brain is interrupted, some brain cells die immediately,
while others remain at risk for death. These damaged cells make up the ischemic
penumbra and can linger in a compromised state for several hours. With timely
treatment these cells can be saved. The ischemic penumbra is discussed in more
detail in the Appendix.
Even though a stroke occurs in the unseen reaches of the brain, the symptoms of
a stroke are easy to spot. They include sudden numbness or weakness, especially
on one side of the body; sudden confusion or trouble speaking or understanding
speech; sudden trouble seeing in one or both eyes; sudden trouble walking,
dizziness, or loss of balance or coordination; or sudden severe headache with no
known cause. All of the symptoms of stroke appear suddenly, and often there is
more than one symptom at the same time. Therefore stroke can usually be
distinguished from other causes of dizziness or headache. These symptoms may
indicate that a stroke has occurred and that medical attention is needed
immediately.
There are two forms of stroke: ischemic - blockage of a blood vessel supplying
the brain, and hemorrhagic - bleeding into or around the brain. The following
sections describe these forms in detail.
Ischemic Stroke
An ischemic stroke occurs when an artery supplying the brain
with blood becomes blocked, suddenly decreasing or stopping blood flow and
ultimately causing a brain infarction. This type of stroke accounts for
approximately 80 percent of all strokes. Blood clots are the most common cause
of artery blockage and brain infarction. The process of clotting is necessary
and beneficial throughout the body because it stops bleeding and allows repair
of damaged areas of arteries or veins. However, when blood clots develop in the
wrong place within an artery they can cause devastating injury by interfering
with the normal flow of blood. Problems with clotting become more frequent as
people age.
Blood clots can cause ischemia and infarction in two ways. A clot that forms in
a part of the body other than the brain can travel through blood vessels and
become wedged in a brain artery. This free-roaming clot is called an embolus and
often forms in the heart. A stroke caused by an embolus is called an embolic
stroke. The second kind of ischemic stroke, called a thrombotic stroke, is
caused by thrombosis, the formation of a blood clot in one of the cerebral
arteries that stays attached to the artery wall until it grows large enough to
block blood flow.
Ischemic strokes can also be caused by stenosis, or a narrowing of the artery
due to the buildup of plaque (a mixture of fatty substances, including
cholesterol and other lipids) and blood clots along the artery wall. Stenosis
can occur in large arteries and small arteries and is therefore called large
vessel disease or small vessel disease, respectively. When a stroke occurs due
to small vessel disease, a very small infarction results, sometimes called a
lacunar infarction, from the French word "lacune" meaning "gap" or "cavity."
The most common blood vessel disease that causes stenosis is atherosclerosis. In
atherosclerosis, deposits of plaque build up along the inner walls of large and
medium-sized arteries, causing thickening, hardening, and loss of elasticity of
artery walls and decreased blood flow.
Hemorrhagic Stroke
In a healthy, functioning brain, neurons do not come into
direct contact with blood. The vital oxygen and nutrients the neurons need from
the blood come to the neurons across the thin walls of the cerebral capillaries.
The glia (nervous system cells that support and protect neurons) form a
blood-brain barrier, an elaborate meshwork that surrounds blood vessels and
capillaries and regulates which elements of the blood can pass through to the
neurons.
When an artery in the brain bursts, blood spews out into the surrounding tissue
and upsets not only the blood supply but the delicate chemical balance neurons
require to function. This is called a hemorrhagic stroke. Such strokes account
for approximately 20 percent of all strokes.
Hemorrhage can occur in several ways. One common cause is a bleeding aneurysm, a
weak or thin spot on an artery wall. Over time, these weak spots stretch or
balloon out under high arterial pressure. The thin walls of these ballooning
aneurysms can rupture and spill blood into the space surrounding brain cells.
Hemorrhage also occurs when arterial walls break open. Plaque-encrusted artery
walls eventually lose their elasticity and become brittle and thin, prone to
cracking. Hypertension, or high blood pressure, increases the risk that a
brittle artery wall will give way and release blood into the surrounding brain
tissue.
A person with an arteriovenous malformation (AVM) also has an increased risk of
hemorrhagic stroke. AVMs are a tangle of defective blood vessels and capillaries
within the brain that have thin walls and can therefore rupture.
Bleeding from ruptured brain arteries can either go into the substance of the
brain or into the various spaces surrounding the brain. Intracerebral hemorrhage
occurs when a vessel within the brain leaks blood into the brain itself.
Subarachnoid hemorrhage is bleeding under the meninges, or outer membranes, of
the brain into the thin fluid-filled space that surrounds the brain.
The subarachnoid space separates the arachnoid membrane from the underlying pia
mater membrane. It contains a clear fluid (cerebrospinal fluid or CSF) as well
as the small blood vessels that supply the outer surface of the brain. In a
subarachnoid hemorrhage, one of the small arteries within the subarachnoid space
bursts, flooding the area with blood and contaminating the cerebrospinal fluid.
Since the CSF flows throughout the cranium, within the spaces of the brain,
subarachnoid hemorrhage can lead to extensive damage throughout the brain. In
fact, subarachnoid hemorrhage is the most deadly of all strokes.
Transient Ischemic Attacks
A transient ischemic attack (TIA), sometimes called a
mini-stroke, starts just like a stroke but then resolves leaving no noticeable
symptoms or deficits. The occurrence of a TIA is a warning that the person is at
risk for a more serious and debilitating stroke. Of the approximately 50,000
Americans who have a TIA each year, about one-third will have an acute stroke
sometime in the future. The addition of other risk factors compounds a person's
risk for a recurrent stroke. The average duration of a TIA is a few minutes. For
almost all TIAs, the symptoms go away within an hour. There is no way to tell
whether symptoms will be just a TIA or persist and lead to death or disability.
The patient should assume that all stroke symptoms signal an emergency and
should not wait to see if they go away.
Recurrent Stroke
Recurrent stroke is frequent; about 25 percent of people who
recover from their first stroke will have another stroke within 5 years.
Recurrent stroke is a major contributor to stroke disability and death, with the
risk of severe disability or death from stroke increasing with each stroke
recurrence. The risk of a recurrent stroke is greatest right after a stroke,
with the risk decreasing with time. About 3 percent of stroke patients will have
another stroke within 30 days of their first stroke and one-third of recurrent
strokes take place within 2 years of the first stroke.
How Do You Recognize Stroke?
Symptoms of stroke appear suddenly. Watch for these symptoms
and be prepared to act quickly for yourself or on behalf of someone you are
with:
- Sudden numbness or weakness of the face, arm, or leg,
especially on one side of the body.
- Sudden confusion, trouble talking, or understanding speech.
- Sudden trouble seeing in one or both eyes.
- Sudden trouble walking, dizziness, or loss of balance or
coordination.
- Sudden severe headache with no known cause.
If you suspect you or someone you know is experiencing any of
these symptoms indicative of a stroke, do not wait. Call 911 emergency
immediately. There are now effective therapies for stroke that must be
administered at a hospital, but they lose their effectiveness if not given
within the first 3 hours after stroke symptoms appear. Every minute
counts!
Risk Factors for a Stroke
Stroke prevention is still the best medicine. The most
important treatable conditions linked to stroke are:
- High blood pressure.Treat it. Eat a balanced
diet, maintain a healthy weight, and exercise to reduce blood pressure. Drugs
are also available.
- Cigarette smoking. Quit. Medical help is
available to help quit.
- Heart disease. Manage it. Your doctor can
treat your heart disease and may prescribe medication to help prevent the
formation of clots. If you are over 50, NINDS scientists believe you and your
doctor should make a decision about aspirin therapy.
- Diabetes. Control it. Treatment can delay
complications that increase the risk of stroke.
- Transient ischemic attacks (TIAs). Seek help.
TIAs are small strokes that last only for a few minutes or hours. They should
never be ignored and can be treated with drugs or surgery.
What Stroke Therapies are Available?
Physicians have a wide range of therapies to choose from when
determining a stroke patient's best therapeutic plan. The type of stroke therapy
a patient should receive depends upon the stage of disease. Generally there are
three treatment stages for stroke: prevention, therapy immediately after stroke,
and post-stroke rehabilitation. Therapies to prevent a first or recurrent stroke
are based on treating an individual's underlying risk factors for stroke, such
as hypertension, atrial fibrillation, and diabetes, or preventing the widespread
formation of blood clots that can cause ischemic stroke in everyone, whether or
not risk factors are present. Acute stroke therapies try to stop a stroke while
it is happening by quickly dissolving a blood clot causing the stroke or by
stopping the bleeding of a hemorrhagic stroke. The purpose of post-stroke
rehabilitation is to overcome disabilities that result from stroke damage.
Therapies for stroke include medications, surgery, or rehabilitation.
Medications
Medication or drug therapy is the most common treatment for
stroke. The most popular classes of drugs used to prevent or treat stroke are
antithrombotics (antiplatelet agents and anticoagulants) and
thrombolytics.
Antithrombotics prevent the formation of blood clots that can become lodged in a
cerebral artery and cause strokes. Antiplatelet drugs prevent clotting by
decreasing the activity of platelets, blood cells that contribute to the
clotting property of blood. These drugs reduce the risk of blood-clot formation,
thus reducing the risk of ischemic stroke. In the context of stroke, physicians
prescribe antiplatelet drugs mainly for prevention. The most widely known and
used antiplatelet drug is aspirin. Other antiplatelet drugs include clopidogrel,
ticlopidine, and dipyridamole. The NINDS sponsors a wide range of clinical
trials to determine the effectiveness of antiplatelet drugs for stroke
prevention.
Anticoagulants reduce stroke risk by reducing the clotting property of the
blood. The most commonly used anticoagulants include warfarin (also known
as Coumadin® ), heparin, and enoxaparin (also known as
Lovenox). The NINDS has sponsored several trials to test the efficacy of
anticoagulants versus antiplatelet drugs. The Stroke Prevention in Atrial
Fibrillation (SPAF) trial found that, although aspirin is an effective therapy
for the prevention of a second stroke in most patients with atrial fibrillation,
some patients with additional risk factors do better on warfarin therapy.
Another study, the Trial of Org 10127 in Acute Stroke Treatment (TOAST), tested
the effectiveness of low-molecular weight heparin (Org 10172) in stroke
prevention. TOAST showed that heparin anticoagulants are not generally effective
in preventing recurrent stroke or improving outcome.
Thrombolytic agents are used to treat an ongoing, acute ischemic stroke caused
by an artery blockage. These drugs halt the stroke by dissolving the blood clot
that is blocking blood flow to the brain. Recombinant tissue
plasminogen activator (rt-PA) is a genetically engineered form of t-PA, a
thombolytic substance made naturally by the body. It can be effective if given
intravenously within 3 hours of stroke symptom onset, but it should be used only
after a physician has confirmed that the patient has suffered an ischemic
stroke. Thrombolytic agents can increase bleeding and therefore must be used
only after careful patient screening. The NINDS rt-PA Stroke Study showed the
efficacy of t-PA and in 1996 led to the first FDA-approved treatment for acute
ischemic stroke. Other thrombolytics are currently being tested in clinical
trials.
Neuroprotectants are medications that protect the brain from secondary injury
caused by stroke. Although no neuroprotectants are FDA-approved for use in
stroke at this time, many are in clinical trials. There are several different
classes of neuroprotectants that show promise for future therapy, including
glutamate antagonists, antioxidants, apoptosis inhibitors, and many others.
Surgery
Surgery can be used to prevent stroke, to treat acute stroke,
or to repair vascular damage or malformations in and around the brain. There are
two prominent types of surgery for stroke prevention and treatment: carotid
endarterectomy and extracranial/intracranial (EC/IC) bypass.
Carotid endarterectomy is a surgical procedure in which a doctor removes fatty
deposits (plaque) from the inside of one of the carotid arteries, which are
located in the neck and are the main suppliers of blood to the brain. As
mentioned earlier, the disease atherosclerosis is characterized by the buildup
of plaque on the inside of large arteries, and the blockage of an artery by this
fatty material is called stenosis. The NINDS has sponsored two large clinical
trials to test the efficacy of carotid endarterectomy: the North American
Symptomatic Carotid Endarterectomy Trial (NASCET) and the Asymptomatic Carotid
Atherosclerosis Trial (ACAS). These trials showed that carotid endarterectomy is
a safe and effective stroke prevention therapy for most people with greater than
50 percent stenosis of the carotid arteries when performed by a qualified and
experienced neurosurgeon or vascular surgeon.
Currently, the NINDS is sponsoring the Carotid Revascularization Endarterectomy
vs. Stenting Trial (CREST), a large clinical trial designed to test the
effectiveness of carotid endarterectomy versus a newer surgical procedure for
carotid stenosis called stenting. The procedure involves inserting a long, thin
catheter tube into an artery in the leg and threading the catheter through the
vascular system into the narrow stenosis of the carotid artery in the neck. Once
the catheter is in place in the carotid artery, the radiologist expands the
stent with a balloon on the tip of the catheter. The CREST trial will test the
effectiveness of the new surgical technique versus the established standard
technique of carotid endarterectomy surgery.
EC/IC bypass surgery is a procedure that restores blood flow to a blood-deprived
area of brain tissue by rerouting a healthy artery in the scalp to the area of
brain tissue affected by a blocked artery. The NINDS-sponsored EC/IC Bypass
Study tested the ability of this surgery to prevent recurrent strokes in stroke
patients with atherosclerosis. The study showed that, in the long run, EC/IC
does not seem to benefit these patients. The surgery is still performed
occasionally for patients with aneurysms, some types of small artery disease,
and certain vascular abnormalities.
One useful surgical procedure for treatment of brain aneurysms that cause
subarachnoid hemorrhage is a technique called "clipping." Clipping
involves clamping off the aneurysm from the blood vessel, which reduces the
chance that it will burst and bleed.
A new therapy that is gaining wide attention is the detachable coil
technique for the treatment of high-risk intracranial aneurysms. A small
platinum coil is inserted through an artery in the thigh and threaded through
the arteries to the site of the aneurysm. The coil is then released into the
aneurysm, where it evokes an immune response from the body. The body produces a
blood clot inside the aneurysm, strengthening the artery walls and reducing the
risk of rupture. Once the aneurysm is stabilized, a neurosurgeon can clip the
aneurysm with less risk of hemorrhage and death to the patient.
Rehabilitation Therapy
Stroke is the number one cause of serious adult disability in
the United States. Stroke disability is devastating to the stroke patient and
family, but therapies are available to help rehabilitate post-stroke patients.
For most stroke patients, physical therapy (PT) is the cornerstone of the
rehabilitation process. A physical therapist uses training, exercises, and
physical manipulation of the stroke patient's body with the intent of restoring
movement, balance, and coordination. The aim of PT is to have the stroke patient
relearn simple motor activities such as walking, sitting, standing, lying down,
and the process of switching from one type of movement to another.
Another type of therapy involving relearning daily activities is occupational
therapy (OT). OT also involves exercise and training to help the stroke patient
relearn everyday activities such as eating, drinking, dressing, bathing,
cooking, reading and writing, and toileting. The goal of OT is to help the
patient become independent or semi-independent.
Speech and language problems arise when brain damage occurs in the language
centers of the brain. Due to the brain's great ability to learn and change
(called brain plasticity), other areas can adapt to take over some of the lost
functions. Speech language pathologists help stroke patients relearn language
and speaking skills, including swallowing, or learn other forms of
communication. Speech therapy is appropriate for any patients with problems
understanding speech or written words, or problems forming speech. A speech
therapist helps stroke patients help themselves by working to improve language
skills, develop alternative ways of communicating, and develop coping skills to
deal with the frustration of not being able to communicate fully. With time and
patience, a stroke survivor should be able to regain some, and sometimes all,
language and speaking abilities.
Many stroke patients require psychological or psychiatric help after a stroke.
Psychological problems, such as depression, anxiety, frustration, and anger, are
common post-stroke disabilities. Talk therapy, along with appropriate
medication, can help alleviate some of the mental and emotional problems that
result from stroke. Sometimes it is also beneficial for family members of the
stroke patient to seek psychological help as well.
References:
National
Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892
Nutritional and Herbal Therapy for Stroke
There are number of food and herbal choices that can help
prevent a stroke.
- Omega-3 fatty acids from salmon, tuna or trout or a
fish oil concentrate (4-10 capsules daily) can inhibit blood clots and reduce
inflammation. They also have a hypotensive effect.
- Calcium and magnesium help lower blood
pressure. Magnesium can improve circulation.
- Garlic prevents blood clots and can lower blood
pressure.
- Green Tea extract can also prevent blood clots,
lowers LDL cholesterol levels and lowers blood pressure.
- Ginkgo Biloba (120-240 mg a day) improves
circulation and memory and prevents blood clots.
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