Previous studies have shown that silent (without symptoms) ischemic lesions--changes in tissue that occur when blood flow to an area of the brain is reduced or blocked--occur more frequently than symptomatic lesions up to three months after stroke, according to background information in the article. Based on this and other findings, researchers hypothesized that silent ischemic lesions on magnetic resonance imaging (MRI) may be a marker for subsequent strokes and other vascular events.

Dong-Wha Kang, M.D., Ph.D., of the National Institute of Neurological Disorders and Stroke, Bethesda, Md., and colleagues studied 120 patients who had an acute ischemic stroke between 2000 and 2002. Each patient had MRI performed within 24 hours of the stroke and on the fifth day after, and 68 underwent follow-up MRI after 30 or up to 90 days. In 2003, 104 of the patients or their caregivers were interviewed to determine if the patients had an additional stroke or had undergone related procedures.

Of these 104 patients, 50 were men and 54 were women, and the average age was 71.3. Silent ischemic lesions were observed on MRI in 42 (40.4 percent) of the patients, including in 35 (33.7 percent) after five days and in 15 (22.1 percent) of the 68 who had 30- or 90-day MRIs. At the 2003 follow-up, eight (7.7 percent) of the total 104 patients had a recurrent ischemic stroke; three (2.9 percent) had a transient ischemic attack (mini-stroke), a stroke with complete recovery within 24 hours; and three (2.9 percent) died from vascular causes during the study's follow-up period. Patients with silent ischemic lesions on the 30- or 90-day MRI had about 6.5 times the odds of having a subsequent ischemic stroke, and those with silent lesions on any MRI had increased odds of death from vascular causes, recurrent ischemic stroke or transient ischemic attack.

"It is a matter of circumstance, rather than tissue pathological features, that determines whether cerebral ischemia is symptomatic or silent," the authors write. "Clinical symptoms depend on the size, location and number of new lesions. Thus, we assume that the pathological process that causes silent lesion recurrence on MRI is the same as the process that causes clinical recurrent strokes. Magnetic resonance imaging may depict pathological changes before the development of clinical stroke symptoms.".

Note: If no author is given, the source is cited instead.

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