Noncontrast computed tomography (CT) has been the standard brain imaging technique used for the initial evaluation of patients with acute stroke symptoms, greatly due to its capacity to rule out the presence of hemorrhage (bleeding), according to background information in the article. Magnetic resonance imaging (MRI) has been suggested as an alternative to CT in an emergency department setting because of its ability to outline the presence, size, location and extent of hyperacute ischemia (blocked blood vessel).
Chelsea S. Kidwell, M.D., from the UCLA Medical Center, Los Angeles, and colleagues examined MRIs and CT scans in 200 patients showing signs of stroke, in order to compare their accuracy in detecting acute bleeding in the brain. The Hemorrhage and Early MRI Evaluation (HEME) study was performed at the UCLA Medical Center and the Suburban Hospital in Bethesda, Md., between October 2000 and February 2003. The average age of patients was 75 years; fifty-five percent of study participants were women. MRI and CT scans were performed within six hours of the patients' onset of stroke symptoms.
Researchers stopped the HEME study early after an unplanned interim analysis revealed that MRI was detecting acute bleeding not detected by CT. In diagnosing any type of bleeding, MRI identified 71 positive patients, while CT identified 29 positive patients. Acute bleeding was diagnosed in 25 participants on both MRI and CT, with four additional patients identified in MRI scans not found in corresponding CT. Chronic bleeding, most often microbleeds, was visualized on 49 patient MRIs, although not on their CT scans.
The authors write: "… MRI may be able to detect regions of hemorrhagic transformation of an acute ischemic stroke not evident on CT. Our study confirms the superiority of MRI for detection of chronic hemorrhage, particularly microbleeds. The role of these findings in the decision-making process for treatment of patients who are candidates for thrombolytic [clot-dissolving] therapy is currently unknown."
They conclude by saying: "… MRI may be acceptable as the sole imaging technique for acute stroke at centers with expertise in interpreting these findings."
(JAMA. 2004; 292: 1823-1830. Available post-embargo at www.jama.com.)
Editor's note: This study was supported in part by the Division of Intramural Research, National Institute of Neurological Disorders and Stroke (NINDS) and grants from the American Heart Association (Dr. Kidwell; AHA Western States Affiliate Fellowship Award, co-author Dr. Leary) and NINDS (Dr. Kidwell, co-authors Algers and Saver). Co-author Dr. Hill was supported in part by the Heart & Stroke Foundation of Alberta/NWT/NU and the Canadian Institutes for Health Research.
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