Strokes, or brain attacks, are a major cause of death and permanent disability. They occur when blood flow to a region of the brain is obstructed and may result in death of brain tissue.
There are two main types of stroke: ischemic and hemorrhagic. Ischemic stroke is caused by blockage in an artery that supplies blood to the brain, resulting in a deficiency in blood flow (ischemia). Hemorrhagic stroke is caused by the bleeding of ruptured blood vessels (hemorrhage) in the brain.
During ischemic stroke, diminished blood flow initiates a series of events (called ischemic cascade) that may result in additional, delayed damage to brain cells. Early medical intervention can halt this process and reduce the risk for irreversible complications.
Stroke, brain stroke, or brain attack, occurs when blood flow in a region of the brain is obstructed by a blockage within a blood vessel (ischemic stroke) or by a ruptured blood vessel (hemorrhagic stroke). Strokes can be life threatening and require immediate medical attention.
Stroke warning signs may come on suddenly or come and go over time. Stroke symptoms include numbness or weakness on one side of the body, confusion, vision problems, dizziness, loss of balance, difficulty walking, severe headache, and difficulty speaking or understanding speech. Serious damage to brain tissue can occur even if stroke symptoms seem mild. Prompt treatment can reduce the risk for severe complications and improve stroke recovery.
Cause of Stroke
Stroke occurs when blood flow to a region of the brain is obstructed, causing brain tissue death.
Ischemic stroke is usually caused by a blood clot in an artery that supplies blood to the brain. Introduction of a foreign substance into the bloodstream may also cause ischemic stroke. For example, an air embolism may occur in deep-sea divers who surface too quickly or may be introduced during intravenous injection.
Hemorrhagic stroke is caused by ruptured blood vessel (aneurysm), arteriovenous malformation (AVM, blood vessel defect), tumor, or traumatic brain injury.
Risk Factors for Stroke
The primary risk factor for ischemic stroke is age (over age 65). High blood pressure (hypertension) and heart disease are also major risk factors. Maintaining healthy blood pressure through diet, exercise, and medication, if necessary, can decrease the risk for stroke.
Atrial fibrillation occurs when muscles in the atria contract too quickly, resulting in an irregular heartbeat (arrhythmia). Arrhythmia alters blood flow and may cause blood clots to form in the heart. These clots can travel through blood vessels to the brain, causing stroke. Atrial fibrillation causes an almost five-fold increase in the risk for stroke.
Recent studies have shown that patients who experience a transient ischemic attack (TIA) or stroke are at increased risk for suffering an additional brain attack.
Risk factors for hemorrhagic stroke include untreated aneurysm, congenital (present at birth) arteriovenous malformations (AVMs), and traumatic brain injury (TBI).
Symptoms of Stroke
A stroke, or brain attack, is a medical emergency that requires immediate medical attention. Because most strokes do not cause severe pain, patients often delay seeking treatment, resulting in extensive brain tissue damage.
Symptoms of stroke depend on the type and which area of the brain is effected. Signs of ischemic stroke usually occur suddenly, and signs of hemorrhagic stroke usually develop gradually. Symptoms include the following:
- Difficulty speaking or understanding speech (aphasia)
- Difficulty walking
- Dizziness or lightheadedness (vertigo)
- Numbness, paralysis, or weakness, usually on one side of the body
- Seizure (relatively rare)
- Severe headache with no known cause
- Sudden confusion
- Sudden decrease in the level of consciousness
- Sudden loss of balance or coordination
- Sudden vision problems (e.g., blurry vision, blindness in one eye)
In transient ischemic attacks (TIAs), one or more symptoms occur suddenly, last a few minutes, and then subside. These “ministrokes” also require immediate medical attention to reduce the risk for damage to brain tissue and to evaluate the risk for stroke.
Diagnosis of Stroke
If stroke is suspected, prompt, accurate diagnosis and treatment is necessary to minimize brain tissue damage. Diagnosis includes a medical history and a physical examination including neurological examination to evaluate the level of consciousness, sensation, and function (visual, motor, language) and determine the cause, location, and extent of the stroke.
Physical examination includes assessing the airway, breathing, and circulation (ABCs) and the vital signs (i.e., pulse, respiration, temperature). The head (including ears, eyes, nose, and throat) and extremities are also examined to help determine the cause of the stroke and rule out other conditions that produce similar symptoms (e.g., Bell’s palsy).
Blood tests (e.g., complete blood count) and imaging procedures (e.g., CT scan, ultrasound, MRI) help the physician determine the type of stroke and rule out other conditions, such as infection and brain tumor.
Imaging Procedures to Diagnose Stroke
When stroke is suspected, computed tomography (CT scan) is performed as soon as possible. CT scan produces x-ray images of the brain and is used to determine the location and extent of hemorrhagic stroke. CT scan usually cannot produce images showing signs of ischemic stroke until 48 hours after onset, so a repeat scan may be performed.
Ultrasound uses high-frequency sound waves to produce images of blood flow through the arteries in the neck that supply blood to the brain (i.e., carotid arteries) and may be used to detect blockage.
Magnetic resonance imaging (MRI scan) with magnetic resonance angiography (MRA) uses a magnetic field to produce detailed images of brain tissue and arteries in the neck and brain, allowing physicians to detect small-vessel infarct (i.e., stroke in small blood vessels deep in brain tissue).
Angiogram involves injecting a contrast agent (dye) into the bloodstream and taking a series of x-rays of blood vessels. This test is used to identify the source and location of arterial blockage and to detect aneurysms and blood vessel defects.
An electrocardiogram may be performed to detect reduced blood flow to the heart (myocardiac ischemia) or irregular heartbeat (cardiac arrhythmia).
Single photon emission computed tomography (SPECT) and positron emission tomography (PET) involve injecting a radioactive substance into the bloodstream and monitoring it as it travels through blood vessels in the brain. These tests allow physicians to detect damaged regions of the brain resulting from reduced blood flow.
Early treatment for stroke can help minimize damage to brain tissue and improve the outcome (prognosis). Treatment depends on whether the stroke is ischemic or hemorrhagic and on the underlying cause of the condition. Hemorrhagic stroke usually requires surgery. The long-term goals of treatment include rehabilitation and prevention of additional strokes.
Treatment for Ischemic Stroke
Initial treatment for ischemic stroke involves removing the blockage and restoring blood flow. Tissue plasminogen activator (t-PA) is a medication that can break up blood clots and restore blood flow when administered within 3 hours of the event. This medication carries a risk for increased intracranial hemorrhage and is not used for hemorrhagic stroke. Mannitol, a diuretic, may be administered intravenously (through an IV) to reduce intracranial pressure during an ischemic stroke.
Antihypertensives such as labetalol (Normodyne) and enalapril (Vasotec) may be used alone or in combination with diuretics to treat high blood pressure (hypertension). Side effects are usually mild and include dizziness, fatigue, and headache.
Antiplatelet agents such as aspirin, clopidogrel bisulfate, and aspirin with dipyridamole (Aggrenox) may be prescribed to reduce the risk for recurrent stroke. Aspirin may also improve the outcome of a stroke when administered within 48 hours. Side effects include stomach pain, heartburn, nausea, and gastrointestinal bleeding. Aggrenox is taken orally, twice a day, and may also cause headache.
Clopidogrel bisulfate (Plavix) is an antiplatelet medication that is taken orally, once a day, to help prevent the formation of blood clots. It is prescribed for patients with atherosclerosis who have had a recent stroke and is used to prevent recurrence. Patients with medical conditions that may cause internal bleeding (e.g., stomach ulcers) should not use clopidogrel.
Side effects include abdominal pain, rash, diarrhea, and headache. Serious side effects (e.g., gastrointestinal hemorrhage) are rare. Physicians and dentists should be informed that a patient is taking clopidogrel before any surgery is scheduled.
Anticonvulsants such as diazepam (Valium) and lorazepam (Ativan) may be prescribed for patients who experience recurrent seizures after a stroke. Side effects include drowsiness, fatigue, and weakness.
Anticoagulants such as warfarin (Coumadin) may be prescribed to prevent the formation of blood clots. Patients taking warfarin may require regular blood tests to monitor coagulation (blood clot formation) and prevent abnormal bleeding.
After Stroke: Expected Outcomes
Prognosis depends on the type of stroke, the degree and duration of obstruction or hemorrhage, and the extent of brain tissue death. Immediate treatment can help improve prognosis in many cases. Most stroke patients experience some permanent disability that may interfere with walking, speech, vision, understanding, reasoning, or memory.
Approximately 70 percent of ischemic stroke patients are able to regain their independence and 10 percent recover almost completely. Approximately 25 percent of patients die as a result of the stroke. The location of a hemorrhagic stroke is an important factor in the outcome, and this type generally has a worse prognosis than ischemic stroke.
According to a scientific statement published by the American Heart Association (AHA) in the journal Stroke (May 2014), exercise is a valuable part of post-stroke care and recovery and can help reduce disability and improve the prognosis for many stroke patients. The AHA reports that exercise—geared to the tolerance of the patient, the stage of the patient’s recovery, and other factor—is an underused part of stroke care and should be prescribed more consistently in the United States.
The American Heart Association also recommends minimizing bed rest in the days following a stroke—having patients sit or stand intermittently if possible—and using stroke rehabilitation programs that emphasize aerobic exercise, strength training, flexibility, and balance.