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StrokeSense : Diagnosis and TreatmentMethods of Diagnosis
If you suspect that you or someone you know is having a stroke or transient ischemic attack (TIA), get to the hospital immediately so a physician can make a diagnosis and start treatment. Besides performing a physical exam and determining the symptoms, the physician will perform or order tests to determine the cause of the TIA or stroke. The physician may first order a computed tomography (CT) scan if he or she suspects a stroke. This scan can determine whether bleeding or a vessel blockage caused a stroke. It also is used to assess a stroke's size and location, as well as if any brain damage has occurred. The physician might perform a neurological examination, which includes an assessment of the cranial nerves, motor skills, coordination and gait, reflexes, and sensory response. Physicians use scales of neurological impairment, including the National Institutes of Health (NIH) stroke scales, to determine the extent of the stroke's effect on brain function. The scales are questionnaires that rate such criteria as how well a person responds to commands or uses language skills. Magnetic resonance imaging (MRI), a noninvasive test that produces pictures of the brain and its arteries, is most useful for detecting the particular area of brain tissue that may have been damaged by ischemic stroke. An MRI also can help determine whether a person who had a stroke also has cytotoxic edema, a condition in which the water content in brain cells increases. Another noninvasive test, magnetic resonance angiography (MRA), is a combination of an MRI and an angiogram (a test that displays an x-ray of blood flow to the brain after dye is injected into the arteries). MRA is used to detect blood vessel changes, including blockage, narrowing, or the presence of an aneurysm. Ultrasound transforms sound waves into electronic images. Carotid ultrasound is used to evaluate the blood flow of the carotid arteries (located in the neck). It shows how much these arteries have narrowed. In this procedure, a transducer is held against the skin over the carotid artery, and it sends an ultrasound signal to a computer that calculates how quickly the blood is moving. This enables the physician to diagnose any blockage in the carotid arteries. Transcranial Doppler ultrasound shows the blood traveling through the arteries to the brain, revealing whether the arteries are narrowed or blocked. Duplex Doppler ultrasound and arteriography are two diagnostic imaging techniques used to determine if a person should undergo a carotid endarterectomy, in which a surgeon removes fatty deposits from the arteries. Ocular pneumoplethysmography (OPG) helps physicians discover if the carotid arteries are delivering blood to the brain and the eyes. The physician may use a cerebral angiography to determine if a TIA or a stroke has occurred. The test uses x-rays to search for abnormalities of the arteries that supply the brain. While the patient is under local anesthesia, the surgeon places a thin, flexible tube in an artery—usually at the groin or elbow—and guides it to a carotid artery. When the catheter is in position, the surgeon injects a dye through it that can be seen on x-rays. The outline of the blood flow through the arteries is then visible on the x-ray. During a xenon CT scan, the person inhales a mix of oxygen and xenon, and then undergoes a CT scan. Xenon's high density increases the contrast between areas of high and low blood flow in the brain. The physician might order radionuclide single-photon emission CT (SPECT) scanning to provide more information about blood flow. During this procedure, the person either swallows or receives an injection containing a radioisotope. The radioisotope travels to a target, where it emits radiation that's detected by a gamma camera. Positron emission tomography (PET) scanning is a type of radionuclide scanning that creates an image based on the function of individual cells within the brain. Unlike CT scanning, PET scanning doesn't produce good structural images. Instead, it offers information about the chemical activity of tissues or organs. It's also used to assess blood flow. PET scanning is extremely important in determining the extent of stroke damage on the brain. On a PET scan of the brain, red and yellow spots indicate high levels of brain activity and blue and black areas indicate low levels of brain activity. PET scanning also can help physicians determine whether brain cells are still chemically active and capable of recovery or if they have died. References
Source of Material: RockHill Communications,
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