Doctors can usually diagnose an ischemic stroke based on the history of events and results of a physical examination. Doctors can usually identify which artery in the brain is blocked based on symptoms (see Brain Dysfunction:IntroductionFigures). For example, weakness or paralysis of the left leg suggests blockage of the artery supplying the area on the right side of the brain that controls the left leg's muscle movements.
Computed tomography (CT) is usually done first. CT helps distinguish an ischemic stroke from a hemorrhagic stroke, a brain tumor, an abscess, and other structural abnormalities. Doctors also measure the blood sugar level to rule out a low blood sugar level (hypoglycemia), which can cause similar symptoms. If available, diffusion magnetic resonance imaging (MRI), which can detect ischemic strokes within minutes of their start, may be done next.
Identifying the precise cause of the stroke is important. If the blockage is a blood clot, another stroke is very likely unless the underlying disorder is corrected. For example, if blood clots result from an abnormal heart rhythm, treating that disorder can prevent new clots from forming and causing another stroke. Tests for causes may include the following:
Electrocardiography (ECG) to look for abnormal heart rhythms
Continuous ECG monitoring (done at home or in the hospital—see Symptoms and Diagnosis of Heart and Blood Vessel Disorders: Continuous Ambulatory Electrocardiography) to record the heart rate and rhythm continuously for 24 hours (or more), which may detect abnormal heart rhythms that occur unpredictably or briefly
Echocardiography to check the heart for blood clots, pumping or structural abnormalities, and valve disorders
Imaging tests—color Doppler ultrasonography, magnetic resonance angiography, CT angiography, or cerebral (standard) angiography—to determine whether arteries, especially the internal carotid arteries, are blocked or narrowed
Blood tests to check for anemia, polycythemia, blood clotting disorders, vasculitis, and some infections (such as heart valve infections and syphilis) and for risk factors such as high cholesterol levels or diabetes
Imaging tests enable doctors to determine how narrowed the carotid arteries are and thus to estimate the risk of a subsequent stroke or TIA. Such information helps determine which treatments are needed.
For cerebral angiography, a thin, flexible tube (catheter) is inserted into an artery, usually in the groin, and threaded through the aorta to an artery in the neck. Then, a dye is injected to outline the artery. Thus, this test is more invasive than other tests that provide images of the brain's blood supply. However, it provides more information (see Common Imaging Tests: Angiography). Cerebral angiography may be done before atheromas are removed surgically or when vasculitis is suspected.
Rarely, a spinal tap (lumbar puncture) is done—for example, after CT, when doctors still need to determine whether strokelike symptoms are due to an infection or whether a subarachnoid hemorrhage is present (see Stroke (CVA): Subarachnoid Hemorrhage). This procedure is done only if doctors are sure that the brain is not under excess pressure (usually determined by CT or MRI).
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Computed tomography (CT) is usually done first. CT helps distinguish an ischemic stroke from a hemorrhagic stroke, a brain tumor, an abscess, and other structural abnormalities. Doctors also measure the blood sugar level to rule out a low blood sugar level (hypoglycemia), which can cause similar symptoms. If available, diffusion magnetic resonance imaging (MRI), which can detect ischemic strokes within minutes of their start, may be done next.
Identifying the precise cause of the stroke is important. If the blockage is a blood clot, another stroke is very likely unless the underlying disorder is corrected. For example, if blood clots result from an abnormal heart rhythm, treating that disorder can prevent new clots from forming and causing another stroke. Tests for causes may include the following:
Electrocardiography (ECG) to look for abnormal heart rhythms
Continuous ECG monitoring (done at home or in the hospital—see Symptoms and Diagnosis of Heart and Blood Vessel Disorders: Continuous Ambulatory Electrocardiography) to record the heart rate and rhythm continuously for 24 hours (or more), which may detect abnormal heart rhythms that occur unpredictably or briefly
Echocardiography to check the heart for blood clots, pumping or structural abnormalities, and valve disorders
Imaging tests—color Doppler ultrasonography, magnetic resonance angiography, CT angiography, or cerebral (standard) angiography—to determine whether arteries, especially the internal carotid arteries, are blocked or narrowed
Blood tests to check for anemia, polycythemia, blood clotting disorders, vasculitis, and some infections (such as heart valve infections and syphilis) and for risk factors such as high cholesterol levels or diabetes
Imaging tests enable doctors to determine how narrowed the carotid arteries are and thus to estimate the risk of a subsequent stroke or TIA. Such information helps determine which treatments are needed.
For cerebral angiography, a thin, flexible tube (catheter) is inserted into an artery, usually in the groin, and threaded through the aorta to an artery in the neck. Then, a dye is injected to outline the artery. Thus, this test is more invasive than other tests that provide images of the brain's blood supply. However, it provides more information (see Common Imaging Tests: Angiography). Cerebral angiography may be done before atheromas are removed surgically or when vasculitis is suspected.
Rarely, a spinal tap (lumbar puncture) is done—for example, after CT, when doctors still need to determine whether strokelike symptoms are due to an infection or whether a subarachnoid hemorrhage is present (see Stroke (CVA): Subarachnoid Hemorrhage). This procedure is done only if doctors are sure that the brain is not under excess pressure (usually determined by CT or MRI).
Source : www.merckmanuals.com
