The Methodist Hospital System. Leading Medicine

Brain Injury May Raise Stroke Risk

Posted on July 1, 2013 in stroke-app

 

Study of more than 1 million people found link but not cause and effect

By Barbara Bronson Gray
HealthDay Reporter

WEDNESDAY, June 26 (HealthDay News) — People who have a traumatic brain injury may be more likely to suffer a stroke, a large new study suggests.

And while the chances of having a stroke are still small, incurring a traumatic brain injury (TBI) may be as big a risk factor as is high blood pressure, said study author Dr. James Burke.

While stroke risk is usually tied to older adults, about 20 percent occur in those under 65, said Burke, a research fellow in the neurology department at the University of Michigan Medical School. “Stroke is not typically associated with young people, and why younger people have strokes is not well understood.”

But when younger adults do suffer a stroke, the effects can be daunting.

Dr. John Volpi, co-director of the Eddy Scurlock Stroke Center in Houston, recalled a patient who had a minor bike accident and seemed just fine. But after just a few days, the man — who was only 45 — had a stroke. “It was a slow recovery, getting back to walking and talking, and because he was an ophthalmologist, it took him a long time to be able to go back to work,” Volpi said.

While study author Burke said stroke prevention has come a long way in the last 20 years or so, acute stroke treatment has seen only one significant advance, the administration of a powerful blood clot destroyer called tissue plasminogen activator (tPA).

Intravenous tPA is used in the first hours after a stroke to help break up blood clots associated with ischemic stroke, in which blood flow to part of the brain is blocked. Ischemic stroke accounts for about 87 percent of all cases, according to the American Heart Association.

“The next place to hit a potential home run [in preventing stroke] is to find other risk factors that could be playing a key role, especially in younger people,” Burke said.

It is unclear how a traumatic brain injury might raise a person’s stroke risk, he added. “TBI patients may have more headaches, more fear of seizures, diet changes, genuine brain rewiring, or they may be affected by the stress of TBI, or atherosclerotic plaques may be activated.”

The study, published online June 26 in the journal Neurology , tapped several databases of adults in California who went to the emergency department or were discharged from a hospital between 2005 and 2009. More than 400,000 people with traumatic brain injury and more than 700,000 people with trauma but no brain injury were included in the study. The average age of all participants was about 50.

About 28 months after the injury, more than 11,000 people — 1.1 percent — had an ischemic stroke. But among those who had trauma but no brain injury, only 0.9 percent had a stroke. While that difference may seem small, it is significant because the overall risk of stroke for people this age is so tiny, Burke explained.

After taking into account factors that can affect the risk of stroke, such as heart disease, high blood pressure, high cholesterol, the severity of the trauma and age, the scientists found that those with TBI were 30 percent more likely to develop a stroke than were those with trauma but no brain injury.

Volpi said the study involved a large number of patients with robust results and high-quality data. Yet, he noted that the connection between trauma and stroke is still unclear. “It could be a cause-and-effect relationship, but we don’t know for sure. It is possible that an injury to the head could lead to an artery being injured,” he said.

The most likely answer to the connection might be that “when the inner tube within the vessel comes apart because it gets a tiny tear from trauma, it allows the blood to push its way into the two layers and stopping or slowing down the flow of blood, which can cause blockage,” Volpi suggested.

He had some practical advice for those at risk for sports injuries. “I’d be asking my doctor, trainer or coach about what kinds of head injuries they expect and what they are doing to prevent head injury,” he said.

Study author Burke remained skeptical about how much his own research really confirms. While there are a fairly sizable number of strokes in people under 65, the risk factors are still quite unclear, he said. “The most I can honestly say is that this study is helping to inform what we should pursue next in research.”

More information

Learn more about stroke from the U.S. Centers for Disease Control and Prevention.

SOURCES: James Burke, M.D., M.S., clinical lecturer, research fellow, department of neurology, University of Michigan Medical School, Ann Arbor; John Volpi, M.D., assistant professor, Weill Cornell Medical College, and co-director, Eddy Scurlock Stroke Center, Houston; June 26, 2013, Neurology

Share and Enjoy

  • Facebook
  • Twitter
  • StumbleUpon
  • Email
  • Reddit
  • Pinterest

Even the smallest stroke can damage brain tissue and impair cognitive function

Posted on January 16, 2013 in stroke-app

Even the smallest stroke can damage brain tissue and impair cognitive function

Blocking a single tiny blood vessel in the brain can harm neural tissue and even alter behavior, a new study from the University of California, San Diego has shown. But these consequences can be mitigated by a drug already in use, suggesting treatment that could slow the progress of dementia associated with cumulative damage to miniscule blood vessels that feed brain cells. The team reports their results in the December 16 advance online edition of Nature Neuroscience.

“The brain is incredibly dense with vasculature. It was surprising that blocking one small vessel could have a discernable impact on the behavior of a rat,” said Andy Y. Shih, lead author of the paper who completed this work as a postdoctoral fellow in physics at UC San Diego. Shih is now an assistant professor at the Medical University of South Carolina.

Working with rats, Shih and colleagues used laser light to clot blood at precise points within small blood vessels that dive from the surface of the brain to penetrate neural tissue. When they looked at the brains up to a week later, they saw tiny holes reminiscent of the widespread damage often seen when the brains of patients with dementia are examined as a part of an autopsy.

These micro-lesions are too small to be detected with conventional MRI scans, which have a resolution of about a millimeter. Nearly two dozen of these small vessels enter the brain from a square millimeter area of the surface of the brain.

“It’s controversial whether that sort of damage has consequences, although the tide of evidence has been growing as human diagnostics improve,” said David Kleinfeld, professor of physics and neurobiology, who leads the research group.

To see whether such minute damage could change behavior, the scientists trained thirsty rats to leap from one platform to another in the dark to get water.

The rats readily jump if they can reach the second platform with a paw or their snout, or stretch farther to touch it with their whiskers. Many rats can be trained to rely on a single whisker if the others are clipped, but if they can’t feel the far platform, they won’t budge.

“The whiskers line up in rows and each one is linked to a specific spot in the brain,” Shih said. “By training them to use just one whisker, we were able to distill a behavior down to a very small part of the brain.”

When Shih blocked single microvessels feeding a column of brain cells that respond to signals from the remaining whisker, the rats still crossed to the far platform when the gap was small. But when it widened beyond the reach of their snouts, they quit.

The FDA-approved drug memantine, prescribed to slow one aspect of memory decline associated with Alzheimer’s disease, ameliorated these effects. Rats that received the drug jumped whisker-wide gaps, and their brains showed fewer signs of damage.

“This data shows us, for the first time, that even a tiny stroke can lead to disability,” said Patrick D. Lyden, a co-author of the study and chair of the department of neurology at Cedars-Sinai Medical Center in Los Angeles. “I am afraid that tiny strokes in our patients contribute—over the long term—to illness such as dementia and Alzheimer’s disease,” he said, adding that “better tools will be required to tell whether human patients suffer memory effects from the smallest strokes.”

“We used powerful tools from biological physics, many developed in Kleinfeld’s laboratory at UC San Diego, to link stroke to dementia on the unprecedented small scale of single vessels and cells,” Shih said. “At my new position at MUSC, I plan to work on ways to improve the detection of micro-lesions in human patients with MRI. This way clinicians may be able to diagnose and treat dementia earlier.” –Susan Brown

 

###

Additional authors include Pablo Blinder, Beth Friedman, Geoffrey Stanley and Philbert S. Tsai, all at UC San Diego. The National Institutes of Biomedical Imaging and Bioengineering, Mental Health, and Neurological Disease and Stroke provided primary funding through grants to Kleinfeld (EB003832, MH085499, and OD006831). Shih was further supported by a postdoctoral fellowship from the American Heart Association.

Share and Enjoy

  • Facebook
  • Twitter
  • StumbleUpon
  • Email
  • Reddit
  • Pinterest