A
stroke (also known as a
cerebrovascular accident) is an event
characterized by either the sudden interruption of the blood supply to part of
the brain or by the rupture of a blood vessel in the brain. Some of the
disabilities that can result from a stroke include paralysis, cognitive
deficits, speech problems, emotional difficulties, problems with activities of
daily living, and pain.
The 2 forms of stroke are
ischemic stroke and
hemorrhagic 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%
of all strokes. Blood clots are the most common cause of artery blockage and
brain infarction and can cause damage in 2 ways. A clot that forms in a
different part of the body can travel through blood vessels and become lodged in
a cerebral artery. This free-roaming clot or
embolus often forms in the
heart. A stroke caused by an embolus is called an
embolic stroke. The
second type of ischemic stroke, called a
thrombotic stroke, is caused by
the formation of a blood clot in one of the cerebral arteries that adheres to
the arterial wall until it grows large enough to obstruct blood flow.
During a
hemorrhagic stroke, an artery in the brain bursts open, spewing
blood into the surrounding tissue, disrupting not only the blood supply but also
the delicate chemical balance neurons require to function. Such strokes account
for approximately 20% of all strokes. Hemorrhage can occur in several ways. One
common cause is a bleeding aneurysm. Another common cause is the imbalance that
occurs when increased arterial pressure is applied to brittle, plaque-encrusted
arterial walls. Hemorrhagic stroke can also occur in a person with an
arteriovenous malformation, a condition characterized by a tangle of
thin-walled, defective blood vessels and capillaries within the brain. Blood
from ruptured cerebral arteries can flow into either the brain tissue (ie,
intracerebral hemorrhage) or into the various spaces surrounding the brain
(ie,
subarachnoid hemorrhage). Subarachnoid hemorrhage is the most deadly
of all strokes because it involves blood contamination of the cerebrospinal
fluid.
A
transient ischemic attack (TIA), or
mini-stroke, differs from a
stroke because its effects usually resolve within 24 hours and leave no residual
deficits. A TIA is considered a warning that a person is at risk for a more
serious stroke.
Scope
About 700,000 strokes occur in the United States each year. About 500,000 of
these are first strokes. Over 160,000 persons die from stroke each year in the
United States. Stroke is also a leading cause of serious long-term disability.
Stroke death rates are higher for black persons than for white persons, even at
younger ages.
Nearly 75% of all strokes occur in persons older than 65 years, but strokes can
occur at any age. The risk of having a stroke more than doubles each decade
after age 55.
About 25% of persons 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 immediately after a stroke, and the risk decreases with time.
The total cost of stroke to the United States is estimated at about $43 billion
per year.
Risk Factors
Persons with > 1 risk factor for stroke have what is called "amplification of
risk." This means that the multiple risk factors compound their destructive
effects and create an overall risk greater than the simple cumulative effect of
the individual risk factors.
Risk factors for stroke beyond a person's control include the following:
- older age;
- male sex;
- black race;
- certain congenital conditions (eg, certain vascular abnormalities);
- recent viral or bacterial infections;
- head and neck injuries; and
- a positive family history of stroke.
In contrast, other risk factors for stroke can sometimes be modified or
controlled. These factors include the following:
- hypertension;
- atherosclerosis;
- heart disease;
- atrial fibrillation (AF);
- diabetes;
- tobacco use;
- hypercholesterolemia;
- heavy alcohol consumption; and
- illicit drug use.
Some risk factors for stroke apply only to women. Primary among these are
pregnancy, childbirth, and menopause. These risk factors are tied to hormonal
fluctuations. Research in the past few decades has shown that high-dose oral
contraceptive use can increase the risk of stroke in women. However, oral
contraceptives currently on the market contain lower doses of estrogen than they
did in the past. Some studies have shown the newer low-dose oral contraceptives
may not significantly increase the risk of stroke in women.
Other studies have demonstrated that pregnancy and childbirth can put a woman at
an increased risk for stroke. Pregnancy increases the risk of stroke as much as
3 to 13 times. As much as 25% of strokes that occur during pregnancy end in
death, and hemorrhagic strokes, though rare, are still the leading cause of
maternal death in the United States.
Several studies have shown that menopause can increase a woman's risk of stroke.
Some studies have suggested that hormone replacement therapy can reduce some of
the effects of menopause and decrease stroke risk.
Symptoms
The following are symptoms of stroke:
- sudden numbness or weakness of the face, arm, or leg, especially on one side of
the body;
- sudden confusion, difficulty talking, or difficulty understanding speech;
- sudden visual disturbance in one or both eyes;
- sudden difficulty walking, dizziness, or loss of balance or coordination; and
- sudden severe headache of unknown cause.
Persons with these symptoms should be evaluated emergently.
The symptoms of stroke in children are different from those in adults and young
adults. A child experiencing a stroke may have seizures, a sudden loss of
speech, a loss of expressive language (including body language and gestures),
hemiparesis, hemiplegia, dysarthria, headache, or fever.
Diagnosis
The use of several diagnostic techniques and imaging tools can help determine
the cause of stroke quickly and accurately. The first step in diagnosis is a
short neurologic examination. Blood tests, electrocardiography, and a brain
imaging study may be performed.
The most widely used imaging procedure for stroke is computed tomography (CT).
The results of this test can quickly provide evidence to rule out a hemorrhage,
can occasionally show a tumor that might cause stroke-like manifestations, and
may even show evidence of early infarction. Infarctions can generally be
discerned on CT about 6 to 8 hours after the onset of stroke symptoms.
Magnetic resonance imaging (MRI) may also be helpful in diagnosing stroke
because magnetic fields are able to detect subtle changes in brain tissue
content. One effect of stroke is the slowing of diffusion through the damaged
brain tissue. MRI can show this type of damage within the first hour after the
onset of stroke symptoms. The benefit of MRI over CT is more accurate and
earlier diagnosis of infarction, especially for smaller strokes, though MRI
shows equivalent accuracy in determining whether hemorrhage is present. MRI is
more sensitive than CT for other types of brain disease, such as brain tumor,
that may have manifestations similar to a stroke.
Other types of MRI procedures, often used for the diagnosis of cerebrovascular
disease and to predict the risk of stroke, are magnetic resonance angiography
and functional magnetic resonance imaging. Magnetic resonance angiography may
detect stenosis of cerebral arteries by mapping the flow of blood. Functional
MRI uses a magnet to pick up signals from oxygenated blood and can show brain
activity through increases in local blood flow.
Finally, duplex Doppler ultrasonography and arteriography may be used to
determine the need for carotid endarterectomy as a means to prevent stroke.
Treatment
The type of stroke therapy a patient should receive is dependent on the stage of
disease. Generally, 3 treatment stages for stroke exist: (1) prevention, (2)
immediate post-stroke therapy, and (3) post-stroke rehabilitation.
Therapies to prevent a first or recurrent stroke are selected on the basis of
treating underlying risk factors for stroke, such as hypertension, AF, and
diabetes, or preventing the widespread blood clot formation that can cause
ischemic stroke in any person. Acute stroke therapies are geared toward trying
to halt the evolution of the 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
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.
These drugs reduce the risk of blood-clot formation, thus reducing the risk of
ischemic stroke. In the context of stroke, antiplatelet drugs are prescribed
primarily for prevention. The most widely known and used antiplatelet drug is
aspirin. Other antiplatelet drugs include clopidogrel, ticlopidine, and
dipyridamole.
Anticoagulants reduce stroke risk by reducing the clotting property of the
blood. The most commonly used anticoagulants include warfarin, heparin, and
enoxaparin. The results of one study showed that, though aspirin is an effective
therapy for the prevention of a second stroke in most patients with AF, some
patients with additional risk factors may derive improved benefits from warfarin
therapy. Another study, which tested the effectiveness of low-molecular-weight
heparin in stroke prevention, 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 arterial blockage. These drugs halt the stroke by dissolving the blood clot
that is blocking blood flow to the brain. Recombinant tissue plasminogen
activator is one such drug and can be effective if given intravenously within 3
hours of stroke symptom onset. It is used only after receiving confirmatory
evidence of an ischemic stroke.
Neuroprotectants are medications that protect the brain from secondary
injury caused by stroke. At this time, no neuroprotectants have received
approval from the US Food and Drug Administration for use in stroke, but many
are in clinical trials. Several different classes of neuroprotectants 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. The 2 prominent types
of surgery for stroke prevention and treatment are
carotid endarterectomy
and
extracranial/intracranial (EC/IC) bypass.
During carotid endarterectomy, plaque is removed from the inside of one of the
carotid arteries. Research had shown that carotid endarterectomy is a safe and
effective stroke prevention therapy for most persons with > 50% stenosis of the
carotid arteries when performed by a qualified and experienced neurosurgeon or
vascular surgeon.
Currently, a large clinical trial designed to test the effectiveness of carotid
endarterectomy versus carotid artery stenting is under way. Stenting involves
the insertion of a catheter into an artery in the leg and threading it through
the vascular system into the narrow stenosis of the carotid artery. Once the
catheter is in place in the carotid artery, a radiologist expands the stent with
a balloon on the tip of the catheter.
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. One study showed that EC/IC does not
seem to provide long-term benefit. This 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 rupture. A new therapy gaining wide attention is the detachable coil
technique for the treatment of high-risk intracranial aneurysms. During this
procedure, 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, the
aneurysm can be clipped with less risk of hemorrhage and death to the patient.
Post-Stroke Rehabilitation
For most patients who have experienced strokes, physical therapy is the
cornerstone of the rehabilitation process. A physical therapist uses training,
exercises, and physical manipulation of an affected patient's body with the
intent of restoring movement, balance, and coordination. The goal of physical
therapy is to have a patient relearn simple motor activities such as walking,
sitting, standing, and 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 a patient affected
by stroke relearn everyday activities such as eating, drinking, dressing,
bathing, cooking, reading, writing, and toileting. The goal of OT is to help the
patient become independent or semi-independent.
Speech language pathologists can help patients who have experienced stroke
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 these patients 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 patients who have had a stroke require psychologic or psychiatric
assistance. Psychologic problems, such as depression, anxiety, frustration, and
anger, are common post-stroke disabilities. Talk therapy, along with appropriate
medication use, can help alleviate some of the mental and emotional problems
that result from stroke. It also may be useful for a patient's family members to
seek psychologic help as well.