Capillary Bottlenecks Make Brain Vulnerable to Stroke

The researchers found that the penetrating arterioles, which connect the blood vessels on the brain's surface with deeper vessels, are a vulnerable link in the network. The obstruction of blood flow resulted in damage to the surrounding brain area, which the researchers report resembled damage seen in the brains of humans.

The researchers say their results support the hypothesis that the penetrating arterioles may be the location of small "silent strokes” that cause the death of sections of brain tissue in humans. The accumulation of damage may lead to memory loss--part of the dementia picture in Alzheimer's and non-Alzheimer's patients--and may be a risk factor for having a larger stroke. The study was published in the January 2, 2007, edition of the journal U.S Proceedings of the National Academy of Sciences (PNAS).

"The blood vessels on the surface of the brain are like a collection of city streets that provide multiple paths to get somewhere,” said co-author David Kleinfeld, a professor of physics at UCSD. "If one of the vessels is blocked, blood flow quickly rearranges itself. On the other hand, the penetrating arterioles are more like freeways. When blocked, the blood flow is stopped or slowed significantly in a large region round the clot.”

So called "silent strokes” have attracted attention recently because magnetic resonance imaging (MRI) has made it possible to follow changes in the brains of individuals as they age. The scans have revealed that, over time, small holes accumulate in the gray matter of many patients, including those who have no obvious behavioral signs of a stroke.



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