An acute ischemic stroke preceded by a smaller transient ischemic attack (TIA), in the same vascular region of the brain, can result in lower clinical deficits, resistance to a second ischemic event, and better functional outcomes. German researchers used MRI to study the concept of ischemic preconditioning in 41 stroke patients.
"Preconditioning means that a TIA prepares brain cells for a subsequent, longer-lasting ischemia, which would otherwise be deadly," explained Dr. Susanne Wegener in a presentation at the 2002 International Stroke Conference in San Antonio. Wegener is an associate professor of neurology at Humboldt University in Berlin.
The patient population consisted of 41 stroke patients. The initial lesion size was determined on diffusion-weighted and perfusion-weighted MRI less than 12 hours after the onset of symptoms. The apparent diffusion coefficient (ADC) and mean transit time (MTT) maps were calculated from this data. The final infarct size was measured 3-9 days after the onset of symptoms using T2-weighted MRI. The researchers excluded patients indicating previous strokes and/or old ipsilateral lesions.
According to the results, ADC lesion volume was 27.5 ml in 34 patients without prior TIA and 10.1 ml in seven patients with prior TIA. MTT lesion volume was 82 ml in patients without prior TIA and 110.6 ml in patients with prior TIA. Final infarct size on T2-weighted MRI was 46.7 ml in 33 patients without prior TIA (33) and 6.2 ml in five patients with TIA.
"The brain cells of our TIA subjects appeared to adjust to the changes in their cellular mechanisms," Wegener said. "Some researchers have said that this is probably the result of angiogenesis after TIA. Our study shows otherwise, that it is not angiogenesis but ischemic preconditioning that leads to smaller infarct from subsequent ischemic stroke."
By Bruce SylvesterAuntMinnie.com contributing writer
March 11, 2002
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