American Family Children's Hospital

New Study Will Track Silent Strokes That Cause Seniors' Cognitive Decline

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A $1.57 million federal grant will allow University of Wisconsin-Madison neuroscientists to determine if they can use non-invasive scans to determine which patients are at highest risk for "silent strokes" that can lead to mental decline.

Researchers believe that "silent strokes" occur for a variety of reasons. One important cause may arise when bits of hardened plaque break off from artery walls and clog the circulation to small areas of the brain. This may occur five times as often as the more noticeable clinical strokes, in which a blood clot blocks the flow and can cause more obvious brain damage.

But these small strokes, while unnoticed, can cause changes in thinking, personality and memory.

"Because of better clinical data, we now know that these strokes are much more prevalent than we had believed and could affect as many as 11 million people a year in the United States," said Dr. Robert Dempsey, chair of neurosurgery at the University of Wisconsin School of Medicine and Public Health and the lead investigator for the new study.

An earlier pilot study by Dempsey and Dr. Tomy Varghese, associate professor of medical physics, showed that ultrasound can be used to create "strain images" of the stability of the atherosclerotic plaque that builds up in the carotid artery, the major source of blood flow to the brain.

This method shows the plaques pulsating with each heart beat, allowing researchers to determine how brittle they were. Further, the pilot study showed that when plaque became unstable, the patient's course was associated with dramatic cognitive declines.

Dempsey said the researchers are particularly interested in identifying patients with greater than 60 percent blockage of these arteries and whose plaque shows evidence of cracking or being brittle. This unstable plaque is most in danger of breaking loose and causing damage in the brain.

They then will use MRI and Doppler scans to detect emboli breaking loose and to look for evidence of these silent strokes in the brain, while also testing patients for cognitive decline.

"If we could better predict who was at risk for these silent strokes, and target therapy for them," Dempsey says, "we could reduce or delay many of the cognitive problems faced by our aging population."

The five-year grant from the National Institute of Neurological Disease and Stroke will allow a team of researchers to study about 72 patients who are to undergo surgery to correct their blockages and are at risk of "silent stroke."

Besides Dempsey and Varghese, other researchers on the grant include:

  • Raghu Vemuganti, associate professor of neurosurgery
  • Sterling Johnson, associate professor of medicine
  • Thomas Cook, biostatistician
  • Bruce Hermann, professor of neurology
  • Howard Rowley, professor of radiology
  • Mark Kliewer, professor of radiology
  • Carol Mitchell, radiology researcher