As people age, plaque made up of lipids (blood fats such as cholesterol and
triglycerides), calcium, and fibrous tissue can build up inside their arteries. Over time, these plaques continue to grow in arterial walls, a process called atherosclerosis or hardening of the arteries. Particles of plaque may break off, or blood clots can form on the surface of the plaques and break off. These particles and blood clots can then travel to the arteries of the brain.
The brain gets most of its blood supply through the large arteries on each side of the neck, called the carotid arteries. Each main carotid artery branches off into the external carotid and internal carotid arteries. The external carotid artery supplies the tissues of the face. The internal carotid artery continues up into the brain and divides into smaller arteries.
If enough plaque has built up in the carotid arteries to interfere with the flow of blood to the brain, or to threaten the development of blood clots, a person is said to have carotid artery disease. Carotid artery disease is present in 30 to 40 percent of ischemic stroke patients. Atherosclerosis can also occur inside the tiny arteries in the brain; narrowed brain arteries are present in 5 to 15 percent of ischemic stroke patients.
Blood clots can also originate from the heart in conditions such as atrial fibrillation, mitral stenosis, and congestive heart failure, and can also cause stroke.
Hemorrhagic strokes occurs in approximately 10 to 15 percent of cases. In hemorrhagic stroke, a blood vessel inside the brain leaks or bursts. As a result, the brain receives less blood. The escaped blood also triggers swelling in the brain (cerebral edema) and the formation of a mass (hematoma), both of which cause pressure to build inside the brain and can quickly damage brain cells. Hemorrhagic stroke is more likely to cause death than ischemic stroke. Approximately 40 to 80 percent of hemorrhagic stroke patients die within 30 days, and one-half of the deaths occur within the first 48 hours.
What are the symptoms?
Symptoms of stroke vary depending on what area of the brain is affected and the severity of the stroke. In general, stroke symptoms come on suddenly (in less than one hour) and may come and go. Ischemic strokes usually do not cause pain. Some hemorrhagic strokes cause a severe headache or unexplained nausea.
Patients who experience a sudden change in their neurologic status should seek help immediately, because most stroke-related brain damage occurs within a few hours of the onset of symptoms.
Stroke symptoms may include:
- Partial loss of vision
- Weakness, tingling, or numbness in one arm and/or leg
- Temporary loss of control of movement in one arm and/or leg
- Inability to pronounce words or speak clearly
- Unsteadiness, vertigo, double vision
- Sudden difficulty swallowing
- Sudden memory loss
- Loss of balance
- Loss of consciousness .
If symptoms go away in less than 24 hours, the patient has experienced a warning sign of a stroke called a transient ischemic attack (TIA), or mini-stroke. Even though TIA symptoms resolve without treatment, they are serious and should be promptly reported to a physician. Unfortunately, not all stroke patients experience warning signs, such as a TIA.
Hemorrhagic strokes are more likely than ischemic strokes to cause the following symptoms:
- Sudden and severe headache, often described as "the worst headache of my life"
- Nausea or vomiting
Risk factors for strokes in general include:
- Advanced age
- Male gender
- African American race
- Having an immediate family member who has had a stroke
- Having had a prior heart attack or stroke
Although patients cannot change the above risk factors, the following risk factors for stroke can be controlled or treated:
Risk factors for hemorrhagic stroke specifically include:
- Aneurysms in brain blood vessels (these are localized weakened/stretched areas in arteries)
- Arteriovenous malformations (AVM, these are malformed blood vessels where larger arteries connect directly to larger veins resulting in much more vigorous blood flow in those blood vessels)
- High blood pressure (especially if poorly controlled) is by far the most common underlying cause for hemorrhagic stroke
To diagnose stroke, the physician will obtain a detailed description of the patient's symptoms and perform a physical examination and a neurological examination. The physical examination may include vision tests and listening with a stethoscope for abnormal sounds called "bruits" in the carotid arteries, which can indicate a blockage.
Depending on these results, the physician may order one or more of the following tests:
- Computed tomography (CT) scan, one of the most important test for diagnosing an evolving stroke. During a CT scan, the scanner takes a series of cross-sectional x-rays of the head. CT scans help the physician determine if an ischemic or hemorrhagic stroke has occurred and the location and extent of the damage.
- Magnetic resonance imaging (MRI), in which magnetic fields and radio waves create detailed images of the brain, often more detailed than CT scanning. Because an MRI takes more time to perform, it is usually not used as the first test in patients suspected of having had a stroke.
- Angiography, also known as arteriography. In this test, a catheter (long, thin tube) is inserted into an artery and is used to inject a material called contrast into the blood vessels. Angiography helps physicians locate areas of blockage in blood vessels and abnormalities such as aneurysms. This test is mainly used if the physician is considering surgery.
- Ultrasound, or echo, in which high-frequency sound waves are used to detect narrowing and reduction of blood flow in carotid arteries.
- Blood tests for immune conditions or clotting disorders.
- Echocardiogram (ultrasound of the heart), which can diagnose underlying heart disorders.
- Electroencephalogram (EEG), which shows the brain's electrical activity and may detect seizures.
Patients who experience stroke are usually treated in the intensive care unit. If necessary, a tube is placed in the mouth to assist breathing, blood pressure is adjusted with medications, fluids are given, and vital signs are closely monitored.
The goal of treating ischemic stroke is to remove the blockage in the blood vessel. If the blockage is caused by a blood clot, the physician may intravenously inject a clot-dissolving drug, such as tissue plasminogen activator (tPA) in a procedure called thrombolysis. Alternatively, a specialized radiologist or cardiologist can thread a catheter to the site of the clot and administer clot-dissolving drugs directly to the site of blockage or remove the clot directly. Although these treatments can be very successful in minimizing stroke damage, they must be initiated as quickly as possible following the onset of a stroke. This underscores the need to seek emergency care as soon as possible.
Several treatments may be used to prevent ischemic stroke, including:
- Lifestyle changes (see below)
- Controlling hypertension and cholesterol abnormalities
- Anticoagulant or antiplatelet medications such as aspirin, clopidogrel (Plavix®), or warfarin (Coumadin®)
- Angiotensin-converting enzyme (ACE) inhibitors
- Carotid endarterectomy, the surgical removal of plaque in the carotid artery
- Carotid stenting, the insertion of a mesh-metal tube to keep the carotid artery open.
Physicians may administer medications, which reduce swelling in the brain. Anti-seizure medications may be given. After the patient is stabilized, surgery or minimally invasive procedures may be performed to stop the bleeding. To perform surgery, the physician cuts into the skull to access the blood vessels in the brain. In minimally invasive treatments, the physician advances tiny instruments to the blood vessels in the brain using long, thin tubes called catheters that are inserted in a blood vessel in the groin. Hemorrhagic stroke treatments may include:
- Removal of the hematoma (pooled blood)
- Aneurysm surgery (clipping), or placing a clip or clamp at the base of an aneurysm. This blocks blood flow to the aneurysm so it cannot bleed
- Endovascular aneurysm treatment (coiling), in which tiny metal coils are placed in the aneurysm via a catheter to prevent blood from flowing through the aneurysm
- Surgery to remove an arteriovenous malformation
- Embolization (administering materials that block the blood vessel through a catheter) or radiotherapy (radiation) to shut down an arteriovenous malformation
- Placing a shunt or performing a procedure called a ventriculostomy to drain excess fluid from the brain (to reduce pressure).
Lifestyle factors can contribute to the development of a stroke. Behavior modifications that can decrease stroke risk include:
- Quitting smoking
- Losing weight
- Exercising regularly
- Controlling high blood pressure and cholesterol abnormalities
- Reducing alcohol intake Specialized cholesterol we offer test that not only measures the amount of cholesterol but also the distribution of the particles that carry this substance)