Posts tagged stroke

May 21, 2012

(Medical Xpress) — People with a curious condition that causes them to apply make-up on only one side of their face, or ignore food on half of their plate, are playing a new role in understanding stroke recovery.

Researchers from the Queensland Brain Institute (QBI) at The University of Queensland have found the condition, a subset of the stroke called ‘unilateral spatial neglect’, tend to have the worst recovery outcomes in regaining lost functioning in their bodies, leading them to believe attention may have an important impact on recovering successfully.

Unilateral spatial neglect is typically caused by strokes on the right hand side of the brain and manifests in patients ignoring the left side of their body.

People with the condition may ignore food on the left hand side of their plate or, if asked to draw a clock, squash all 12 numbers into the right side of the clock face, leaving the other side blank.

They may also fail to shave, or to put make-up on the left side of their faces and. In severe cases, they behave as though the left side of their world does not exist.

“We know that brain plasticity plays a critical role in recovering from stroke,” says Professor Jason Mattingley, who holds the Foundation Chair in Cognitive Neuroscience at The University of Queensland.

“The fact that people with spatial neglect tend to have poorer recovery of motor function suggested to us that attention may be important for guiding plasticity following stroke.”

Current research being undertaken by the Mattingley laboratory is exploring this link.

“What we’re trying to do is explore what effect attention has on brain plasticity, and how attention might be used in neurorehabilitation” says Professor Mattingley.

Volunteers first undergo a magnetic resonance imaging (MRI) scan, which provides researchers with a three-dimensional picture of the brain.

“In terms of their structure, brains are like fingerprints – no two are exactly the same, even though superficially they seem very similar,” Professor Mattingley explains.

The MRI scan allows researchers to guide a transcranial magnetic stimulation (TMS) coil into position upon a volunteer’s scalp.

The device induces a small electrical current in the underlying brain tissue, causing it to become more active.

The researchers specifically target a part of the motor cortex that controls the thumb muscle in the left hand.

“It’s well established that the more often neurons activate at the same time, the more likely they are to communicate efficiently in the future. This is how the brain learns,” says Professor Mattingley.

“We’re exploiting that general principle in this research.”

Dr Marc Kamke, Research Fellow at QBI explains: “By adjusting the type of brain stimulation delivered we can artificially induce short-term changes that resemble naturally-occurring plasticity.”

But what the researchers have found is that the effects of stimulation upon a brain’s plasticity are dependent on attention.

“When we ask people to undertake a visual task that is irrelevant to the brain stimulation, but that demands a great deal of their attention, we observe a reduction in plasticity,” Dr Marc Kamke explains.

“When the task does not require much attention, however, the brain’s plastic response is apparent.”

“These results show that attention plays an important role in guiding brain plasticity,” says Professor Mattingley.

He adds, “while practical applications remain several steps away, this knowledge may ultimately help us develop more effective strategies for physical therapy after stroke.”

The results of the research, which was funded by the National Health and Medical Research Council of Australia, are published this week in The Journal of Neuroscience.

Provided by University of Queensland 

Source: medicalxpress.com

May 14, 2012

Following a stroke, factors as varied as blood sugar, body temperature and position in bed can affect patient outcomes, Loyola University Medical Center researchers report.

In a review article in the journal MedLink Neurology, first author Murray Flaster, MD, PhD and colleagues summarize the latest research on caring for ischemic stroke patients. (Most strokes are ischemic, meaning they are caused by blood clots.)

"The period immediately following an acute ischemic stroke is a time of significant risk,” the Loyola neurologists write. “Meticulous attention to the care of the stroke patient during this time can prevent further neurologic injury and minimize common complications, optimizing the chance of functional recovery.”

Stroke care has two main objectives – minimizing injury to brain tissue and preventing and treating the many neurologic and medical complications that can occur just after a stroke.

The authors discuss the many complex factors that affect outcomes. For example, there is considerable evidence of a link between hyperglycemia (high blood sugar) and poor outcomes after stroke. The authors recommend strict blood sugar control, using frequent finger-stick glucose checks and aggressive insulin treatment.

For each 1 degree C increase in the body temperature of stroke patients, the risk of death or severe disability more than doubles. Therapeutic cooling has been shown to help cardiac arrest patients, and clinical trials are underway to determine whether such cooling could also help stroke patients. Until those trials are completed, the goal should be to keep normal temperatures (between 95.9 and 99.5 degrees F).

Position in bed also is important, because sitting upright decreases blood flow in the brain. A common practice is to keep the patient lying flat for 24 hours. If a patient has orthopnea (difficulty breathing while lying flat), the head of the bed should be kept at the lowest elevation the patient can tolerate.

The authors discuss many other issues in stroke care, including blood pressure management; blood volume; statin therapy; management of complications such as pneumonia and sepsis; heart attack and other cardiac problems; blood clots; infection; malnutrition and aspiration; brain swelling; seizures; recurrent stroke; and brain hemorrhages.

Studies have shown that hospital units that specialize in stroke care decrease mortality, increase the likelihood of being discharged to home and improve functional status and quality of life.

All patients should receive supportive care — including those who suffer major strokes and the elderly. “Even in these populations, the majority of patients will survive their stroke,” the authors write. “The degree of functional recovery, however, may be dramatically impacted by the intensity and appropriateness of supportive care.”

Provided by Loyola University Health System

Source: medicalxpress.com

ScienceDaily (Apr. 24, 2012) — Stanford University School of Medicine neuroscientists have demonstrated, in a study published online April 24 in Stroke, that a compound mimicking a key activity of a hefty, brain-based protein is capable of increasing the generation of new nerve cells, or neurons, in the brains of mice that have had strokes. The mice also exhibited a speedier recovery of their athletic ability.

These results are promising, because the compound wasn’t administered to the animals until a full three days after they had suffered strokes, said the study’s senior author, Marion Buckwalter, MD, PhD, an assistant professor of neurology and neurological sciences. This means that the compound works not by limiting a stroke’s initial damage to the brain, but by enhancing recovery.

This is of critical significance, said Buckwalter, a practicing clinical neurologist who often treats recently arrived stroke patients in Stanford Hospital’s intensive care unit.

"No existing therapeutic agents today enhance recovery from stroke," Buckwalter said. "The only approved stroke drug, tissue plasminogen activator, can bust up clots that initially caused the stroke but does nothing to stimulate the restoration of brain function later." Furthermore, to be effective, tPA has to be given within four and a half hours after a stroke has occurred, she added. "In real life, many people don’t get to the hospital that quickly. They may live alone or have their stroke while sleeping, or they and the people close to them didn’t recognize the stroke’s symptoms well enough to realize they’d just had one."

Looking for an alternative, Buckwalter chose to focus on a compound called LM22A-4, which had shown promise in previous research. LM22A-4 is a small molecule whose bulk is less than one-seventieth that of the brain protein it mimics: brain-derived neurotrophic factor, a powerful and long-studied nerve growth factor. BDNF is critical during the development of the nervous system and known to be involved in important brain functions including memory and learning.

Stem-cell therapy, while an exciting prospect, is a relatively invasive and expensive way to replace lost or damaged tissue. A drug that could achieve similar results in such a delicate and complex organ as the brain would be a welcome development.

Read more …

April 2nd, 2012

Therapy to mend parts of the brain damaged by strokes has moved a step closer, thanks to research at Monash University’s Australian Regenerative Medicine Institute (ARMI) and the Florey Neuroscience Institutes (FNI).

Scientists, James Bourne and Jihane Homman-Ludiye, of ARMI, and Tobias Merson, of FNI, have discovered precursor cells in the visual processing region of the brains of young marmoset monkeys which can form new brain cells in a culture dish.

The work, published recently in the journal, PLoS One, raises the possibility of new therapies for victims of brain injuries such as stroke.

Commenting on the work, Stem Cells Australia’s Professor Martin Pera said “These results, which point strongly to the existence of stem cells in the primate cortex, have important implications for understanding normal brain function and add to a growing body of evidence that stem or progenitor cells may participate in the repair of injuries to this critical region of the brain.”

The team isolated a type of cell from the brain tissue of two-week-old marmoset monkeys, which have similar brains to humans.

They exposed the cells to various combinations of growth factors – proteins that promote cell proliferation – to see if the cells would multiply and form neurons in the culture dish.

Some of the cells started to multiply to form clusters of cells called neurospheres – the forerunners of mature brain cells – when treated with two specific growth factors. This puts them in a class of cells called neural progenitors. Like stem cells, these cells can convert into specialist cells to form various tissues.

It was once thought that our full complement of brain cells was fixed at birth. That view has been toppled in recent decades with the discovery of stem cells in the human brain that can form new neurons in adulthood, said Dr Merson, a neuroscientist.

But until now, those cells have been thought to be limited to two regions of the brain, including the hippocampus, which is involved in memory and learning.

The team’s breakthrough suggests that cells with the ability to form new neurons after birth are much more widespread in the brain. The cells under investigation in this latest research were isolated from the primary visual cortex, the brain structure at the back of the head involved in the processing of stimuli from the eyes. “This structure is very big in humans and other primates and is often affected by brain injury,” Dr Bourne said.

“Our results support the view that this region of the brain has the potential to generate new neurons at later stages than once thought,” Dr Merson said. “We were surprised at how easily we were able to generate the proliferating neurospheres. We were able to propagate them, and keep them in culture for up to a year.”

He said other regions of the brain involved in sensory processing could harbour similar cells.

The scientists plan further research to see if the production of new neurons after birth occurs naturally in the primary visual cortex, and whether the mechanism could be activated after injury.

“It could be plausible to manipulate the progenitor cells to produce more neurons,” Dr Bourne said.

Source: Neuroscience News

A DRUG which minimises brain damage when given three hours after stroke has proved successful in monkeys and humans.

A lack of oxygen in the brain during a stroke can cause fatal brain damage. There is only one approved treatment - tissue plasminogen activator - but it is most effective when administered within 90 minutes after the onset of stroke. Immediate treatment isn’t always available, however, so drugs that can be given at a later time have been sought.

In a series of experiments, Michael Tymianski and colleagues at Toronto Western Hospital in Ontario, Canada, replicated the effects of stroke in macaques before intravenously administering a PSD-95 inhibitor, or a placebo. PSD-95 inhibitors interfere with the process that triggers cell death when the brain is deprived of oxygen.

To test its effectiveness the team used MRI to measure the volume of damaged brain for 30 days following the treatment, and conducted behavioural tests at various intervals within this time.

Monkeys treated with the PSD-95 inhibitor one hour after stroke had 55 per cent less damaged tissue in the brain after 24 hours and 70 per cent less after 30 days, compared with those that took a placebo. These animals also did better in behavioural tests. Importantly, the drug was also effective three hours after stroke (Nature, DOI: 10.1038/nature10841).

An early stage clinical trial in humans, run by firm NoNO in Ontario has also seen positive results.

Source: New Scientist