Physicians working in emergency rooms typically do a physical examination of stroke patients, including a standard CT scan of the head. They also ask them or their families a series of questions about symptoms to assess the location and nature of the stroke. A standard CT scan can quickly determine whether the stroke is ischemic or hemorrhagic.
However, high-speed helical CT scans (sometimes called spiral CT), which use a contrast dye, give physicians a view of blood flow inside vessels and the pattern of blood distribution throughout the brain. Helical scanners also allow them to quickly determine if a stroke is ischemic and find where a blockage exists, says study author Michael H. Lev, M.D. The scan can also show the doctor if the vessel is partially or completely blocked, and can show which areas of the brain are not getting enough blood.
"The bottom line is that this is a convenient, cost-effective, minimally invasive way to rapidly get more information that can help acute stroke patients," says Lev. "Most emergency departments in the U.S. have a CT scanner, and the majority are helical scanners. Our study shows they can be used for the brain."
Information from these scans could help physicians assess how best to treat ischemic stroke patients. "It may turn out that the patient isn't having a stroke at all, as happened with four of our patients," says Lev, who is director of the neurovascular laboratory at Massachusetts General Hospital and an assistant professor of radiology at Harvard Medical School in Boston. "It may be a seizure, a migraine headache, or a drastic drop in blood sugar mimicking a stroke."
About 600,000 Americans suffer a first or recurrent stroke each year and about 167,000 of them die. The two major types of stroke are ischemic, caused by a blood clot that blocks a vessel and prevents oxygen-rich blood from reaching a portion of the brain, and hemorrhagic, which occurs when a blood vessel leaks or ruptures.
The only approved therapy for acute ischemic stroke is a clot-busting (thrombolytic) drug either through the veins within three hours after the onset of symptoms, or by infusing it directly into a brain artery, usually within six hours. Thrombolytic drugs do not benefit people with hemorrhagic strokes, and can worsen the bleeding in the brain.
At Massachusetts General, helical CT scans are standard for stroke patients brought to the emergency room. "We had established helical CT as an accurate technique for determining where the damage occurs," says Lev. "The question for our study was to find out how useful it is in diagnosing stroke in addition to what we were using already."
He and his colleagues selected the medical records of 40 acute stroke patients (23 men and 17 women) who had received helical CT scans. Neurologists on the hospital's stroke team reviewed each case. They answered a series of questions at five points in the patients' assessments.
The first point was when the patient's physical examination, symptoms and initial CT scan without the contrast dye were completed. The last was when all the data, including results from the helical CT scan, was available.
At each point the neurologists were asked to give the stroke location, how much brain tissue was affected, which blood vessel was obstructed, and the severity of the stroke. Their answers were compared to the final assessment made after the patient had been released from the hospital.
The average accuracy of the neurologists' answers between their first and final stroke assessments rose from 40 percent to 80 percent for stroke location and from 40 percent to 78 percent in identifying the blocked vessel. Determining the brain area affected by the stroke rose from 55 percent to 83 percent and the accuracy of their classification increased from 55 percent to 88 percent.
"As the neurologists gained information about the patients, their assessment of the stroke became more accurate," says Lev. "The difference in stroke assessment was substantial after doctors saw results from the helical CT."
This work was supported in part by grants from the National Institutes of Health.
Co-authors are Mustapha A. Ezzeddine, M.D. (lead author); Colin T. McDonald, M.D.; Guy Rordorf, M.D.; Jamary Oliveira-Filho, M.D.; Fatma Gul Aksoy, M.D.; Jeffrey Farkas, M.D.; Alan Z. Segal, M.D.; Lee H. Schwamm, M.D.; R. Gilberto Gonzalez, M.D., Ph.D.; and Walter J. Koroshetz, M.D.
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