Posts tagged stroke
Articles and news from the latest research reports.
Researchers find far-reaching, microvascular damage in uninjured side of brain after stroke
While the effects of acute stroke have been widely studied, brain damage during the subacute phase of stroke has been a neglected area of research. Now, a new study by the University of South Florida reports that within a week of a stroke caused by a blood clot in one side of the brain, the opposite side of the brain shows signs of microvascular injury.
Stroke is a leading cause of death and disability in the United States, and increases the risk for dementia.
“Approximately 80 percent of strokes are ischemic strokes, in which the blood supply to the brain is restricted, causing a shortage of oxygen,” said study lead author Svitlana Garbuzova-Davis, PhD, associate professor in the USF Department of Neurosurgery and Brain Repair. “Minutes after ischemic stroke, there are serious effects within the brain at both the molecular and cellular levels. One understudied aspect has been the effect of ischemic stroke on the competence of the blood-brain barrier and subsequent related events in remote brain areas.”
Using a rat model, researchers at USF Health investigated the subacute phase of ischemic stroke and found deficits in the microvascular integrity in the brain hemisphere opposite to where the initial stroke injury occured.
The study was published in the May 10, 2013 issue of PLOS One.
The USF team found that “diachisis,” a term used to describe certain brain deficits remote from primary insult, can occur during the subacute phase of ischemic stroke. The research discovered diachisis is closely related to a breakdown of the blood-brain barrier, which separates circulating blood from brain tissue.
In the subacute phase of an ischemic stroke, when the stroke-induced disturbances in the brain occur in remote brain microvessels, several areas of the brain are affected by a variety of injuries, including neuronal swelling and diminished myelin in brain structures. The researchers suggest that recognizing the significance of microvascular damage could make the blood-brain barrier (BBB) a therapeutic “target” for future neuroprotective strategies for stroke patients.
The mechanisms of BBB permeability at different phases of stroke are poorly understood. While there have been investigations of BBB integrity and processes in ischemic stroke, the researchers said, most examinations have been limited to the phase immediately after stroke, known as acute stroke. Their interest was in determining microvascular integrity in the brain hemisphere opposite to an initial stroke injury at the subacute phase.
Accordingly, this study using rats with surgically-simulated strokes was designed to investigate the effect of ischemic stroke on the BBB in the subacute phase, and the effects of a compromised BBB upon various brain regions, some distant from the stroke site.
“The aim of this study was to characterize subacute diachisis in rats modeled with ischemic stroke,” said co-author Cesar Borlongan, PhD, professor and vice chairman for research in the Department of Neurosurgery and Brain Repair and director of the USF Center for Aging and Brain Repair. “Our specific focus was on analyzing the condition of the BBB and the processes in the areas of the brain not directly affected by ischemia. BBB competence in subacute diachisis is uncertain and needed to be studied.”
Their findings suggest that damage to the BBB, and subsequent vascular leakage as the BBB becomes more permeable, plays a major role in subacute diachisis.
The increasing BBB permeability hours after the simulated stroke, and finding that the BBB “remained open” seven days post-stroke, were significant findings, said Dr. Garbuzova-Davis, who is also a researcher in USF Center for Aging and Brain Repair. “Since increased BBB permeability is often associated with brain swelling, BBB leakage may be a serious and life-threatening complication of ischemic stroke.”
Another significant aspect was the finding that autophagy — a mechanism involving cell degradation of unnecessary or dysfunctional cellular components —plays a role in the subacute phase of ischemia. Study results showed that accumulation of numerous autophagosomes within endothelial cells in microvessels of both initially damaged and non-injured brain areas might be closely associated with BBB damage.
Autophagy is a complex but normal process usually aimed at “self-removing” damaged cell components to promote cell survival. It was unclear, however, whether the role of autophagy in subacute post-ischemia was promoting cell survival or cell death.
More than 30 percent of patients who survive strokes develop dementia within two years, the researchers noted.
“Although dementia is complex, vascular damage in post-stroke patients is a significant risk factor, depending on the severity, volume and site of the stroke,” said study co-author Dr. Paul Sanberg, USF senior vice president for research and innovation. “Ischemic stroke might initiate neurodegenerative dementia, particularly in the aging population.”
The researchers conclude that repair of the BBB following ischemic stroke could potentially prevent further degradation of surviving neurons.
“Recognizing that the BBB is a therapeutic target is important for developing neuroprotective strategies,” they said.
Stroke turned ex-con into rhyming painter
Name: Tommy McHugh
Disorder: Sudden artistic output following brain damage
“I was sitting on the toilet. I suddenly felt an explosion in the left side of my head and ended up on the floor. I think the only thing that kept me conscious was that I didn’t want to be found with my pants down. Then the other side of my head went bang! I woke up in hospital and looked out of the window to see the tree was sprouting numbers. 3, 6, 9. Then I started talking in rhyme…”
Ten days after having a subarachnoid haemorrhage – a stroke caused by bleeding in and around the brain – Tommy McHugh, an ex-con who’d been in his fair share of scraps, became a new man, with a personality that nobody recognised.
When he was a young man, Tommy did time in prison. But after his stroke at age 51, everything changed. “I could taste the femininity inside of myself,” he said. “My head was full of rhymes and images and pictures.”
Not only did he feel a sudden urge to write poetry, but he also began to paint and draw obsessively for up to 19 hours a day. He was never artistic before – in fact, he joked that he’d never even been in an art gallery “except to maybe steal something”.
Desperate to find out what was going on, Tommy wrote to several neuroscientists and end up working closely with Alice Flaherty at Harvard Medical School and Mark Lythgoe at University College London.
Going Zen
Flaherty says the haemorrhage sent blood squirting around the brain surface, affecting a lot of areas. It left Tommy unusually emotional and unable to hurt anyone, “like Zen monks sweeping steps before they walk,” says Flaherty. “Everything strikes him as beautiful and cosmically meaningful.”
Scanning Tommy’s brain was impossible after an operation to treat the stroke damage left him with a piece of metal in his head. Instead, Lythgoe performed a neuropsychological evaluation. Tommy’s IQ was in the normal range. However, he showed verbal disinhibition – he tended to talk a lot – and had difficulty with tests that required him to switch between different cognitive tasks. All of which suggested problems with the frontal lobes.
The frontal lobes play a vital role in abstract thought and creativity. They are constantly bombarded with raw sensory data from the world around us, most of which is deemed irrelevant by the brain and screened from conscious awareness. Blocking this inhibition using magnetic pulses can make people more creative, even unleashing savant-like skills.
“That’s what Tommy’s mind does all the time,” says Lythgoe. Everything he heard and saw triggered a stream of associations that he found difficult to stop. Tommy saw it as having a brain that shows him “endless, endless corridors”. He said his paintings represented a snapshot of a millisecond in his brain.
“I’ll paint three or six or nine pictures at a time. I see those numbers in my head all the time. Canvases became too costly, so I started painting the ceilings and the wallpaper and the floor. I can’t stop painting and sculpting. Give me a mountain and I’ll turn it into a profile. If you give me a bare tree I’ll change it, so when spring come all the leaves will create the face, the mouth, the lips. Without hurting the tree.”
Offering advice for others with brain damage, he said that people who have had strokes need to learn not to think of themselves as ill, with the dangers of depression that can bring. “Some repairs to the brain are constructive, some are negative. One has to learn to develop one’s damaged brain, adapt and start to live again. You can either sit on your bum or look in the mirror and say ‘I’m alive’.”
He wouldn’t even have wanted his old mind back: “The most wonderful thing that happened to Tommy McHugh,” he laughed, “is having a stroke while doing a poo.”
He wouldn’t have changed a thing. “My two strokes have given me 11 years of a magnificent adventure that nobody could have expected.”
Tommy McHugh passed away on 19 September 2012, having spoken to New Scientist several times that year. Samples of his artwork can be viewed on his website.
Five “sudden symptoms” of stroke: Recognizing these could save a life - even a young life
Stroke is the fourth-leading cause of death in the United States. Each year an estimated 795,000 people in this country experience a stroke.* That’s approximately the equivalent of every man, woman and child living in Anaheim and Long Beach combined. But did you know that stroke is also the No. 1 cause of adult disability?
Even more surprising, stroke is no longer a disease only of the elderly. Nearly 20 percent of strokes occur in people younger than age 55, and over the past decade, the average age at stroke occurrence has dropped from 71 to 69.
“The good news,” says Patrick D. Lyden, MD, chair of Neurology and director of the Stroke Program at Cedars-Sinai Medical Center, “is that quickly recognizing the signs of stroke and seeking immediate medical care from stroke specialists can minimize the effects of the disease or even save a life. And just as important as knowing the symptoms is the knowledge that regardless of an individual’s age, those symptoms need to be treated as the emergency that they are.”
- Sudden numbness or weakness of the face, arm or leg on one side of the body.
- Sudden confusion, trouble speaking or understanding.
- Sudden trouble seeing on one side.
- Sudden, severe difficulty walking, dizziness, loss of balance or coordination.
- Sudden, severe headache with no known cause.
It is important to emphasize the words “sudden” and “severe” and the number “one.” Any of these symptoms can occur in a mild, fleeting way and not be worrisome, but if any one of them comes on suddenly and is quite severe, it could signal the onset of a stroke, which increasingly is described as a “brain attack,” because like a heart attack, a stroke requires immediate action to improve the odds against disability and death.
Time is brain
The National Stroke Association estimates that two-thirds of stroke survivors have some disability.
“Clot-busting” drugs make it possible in some cases to stop a stroke in progress and even reverse damage. But the crucial element is time. If given within three hours of onset, the drugs improve outcomes by about 30 percent.
Not every hospital or stroke center has the facilities, staff or resources to provide complete care for every stroke patient, but many hospitals and health authorities are collaborating to establish regional stroke-treatment networks to be sure that even the most complex cases are rapidly transferred to a center with the needed level of care.
(Image: National Stroke Association)
New therapy device enables stroke victims to recover further
Scientists from Nanyang Technological University (NTU) have developed a new stroke rehabilitation device which greatly improves recovery in stroke patients.
Thanks to this invention, stroke patients who had undergone conventional rehabilitation for a year or more and had hit a plateau in their recovery, managed to make significant progress in their ability to carry out everyday tasks.
Some of these long-term stroke sufferers have recovered up to 70 per cent of motor function clinical scores in just a month during the trial.
The new stroke therapy system, known as Synergistic Physio-Neuro Platform (SynPhNe), is currently undergoing thorough clinical investigations and more feasibility trials at local hospitals.
In use for 150 therapy hours, it has not had any side effects so far. Patients who tried SynPhNe also said they experienced little fatigue while using this easy-to-use system.
Developed by Dr John Heng, a senior research fellow at NTU’s School of Mechanical and Aerospace Engineering and his PhD student, Mr Banerji Subhasis, this system gives hope to frustrated patients who want to see more progress after completing conventional rehabilitation therapies.
The NTU research team of four has published over 11 scientific papers since 2008 on the principles of the system, its effectiveness and ease of use.
“While current rehabilitation systems do benefit many patients, there are also other patients who still have difficulties performing everyday activities like holding a fork or drinking from a cup, despite the usual rehab sessions,” said Dr Heng.
“SynPhNe works by giving real-time feedback to the patients on what is happening in their mind and in their muscles. Patients using SynPhNe know where their problems lie and can slowly work towards overcoming each problem, instead of feeling frustrated and going through a painful, expensive and prolonged trial-and-error process when their improvements are not visible.”
How it works
SynPhNe consists of patented computer software connected to a specially designed headset with neural sensors and a sensor arm glove. The device is designed to be worn easily by stroke patients who usually have control of only one arm.
These sensors provide feedback on the stress, attention, and relaxation levels of the mind and which muscles are being activated or inhibited by the patient. The software contains instructional videos for limb movements which the patient can mimic to improve his/her performance of various tasks.
Sensor information is displayed in real time via the computer screen so that the patient is aware of what is happening in his mind and body while undergoing the rehabilitation exercises.
Dr Heng said that while multi-model associative learning is known to be useful in the development of babies and in education, it is the first time that their research team is adapting it for stroke therapy. Tested on 10 patients so far, it has shown to be very effective in accelerating the recovery in stroke patients.
In associative learning, a patient will find out the link between cause and effect, or intent and physical result. The patient learns what he/she wants to do and what is actually happening with their limbs. This helps the patient to self-correct movements to match intended actions.
“For example, if a patient wants to move his wrist, but his wrist is not moving, SynPhNe will be able to show him that his mind had sent out a signal, his muscles have received it, but because supporting and opposing muscles are clenched, he will need to relax the opposing muscle in order to move his wrist,” Mr Subhasis explained.
“Another common problem is that the patient may feel stressed while undergoing therapy, which affects his muscle control. So by showing the stress level on the screen, SynPhNe will teach the patient how to control his breathing and posture to regain his balance and composure so that he can continue with the exercises.
“In short, SynPhNe makes patients aware of what is happening with their bodies so they learn how to relax their mind and muscles. This helps them to re-learn simple actions like holding a pen or a cup which may be arduous tasks for stroke victims.”
Ramping up patient trials
Patient trials are still on-going and 10 patients have undergone the trial for 12 sessions, each lasting 90 minutes. Over a four-week period, they have all shown some improvement on the clinical scales. It was found that patients with hand control and hand weakness problems improved the most, in several cases, up to 70 per cent.
The scientists started the patient trials in October 2012 at Tan Tock Seng Hospital and are embarking on another similar trial at the National University Hospital. Talks are underway to start another trial at Singapore General Hospital and in India.
SynPhNe, which took over five years to develop, have also won successive grants from the National Medical Research Council, the National Research Foundation’s Proof-of-Concept grant and Singapore-MIT Alliance for Research and Technology (SMART)’s Innovation Grant.
Start-up to look into commercialisation
Apart from conducting further trials involving 50 more patients, the next step for the scientists is to form a start-up company to turn the SynPhNe prototype into a portable stroke therapy kit for home use. This kit is expected to be cheaper than most robotic rehabilitation systems in the market which may cost over tens of thousands of dollars.
“This reduction in cost will allow for perhaps a rental or subsidy scheme for patients who wish to practise in the convenience of their own home instead of having to go to rehabilitation centres. It has the added advantage of providing constant updates of instructional videos and exercises to match the patient’s improvement and can even send their reports to their therapists via the device’s Wi-Fi capabilities,” Prof Heng added.
The idea to develop SynPhNe was inspired by the mind-and-body-as-one philosophy preached in traditional practices such as Taichi, Aikido and Yoga, and the health benefits they bring.
Mr Subhasis, a martial arts and yoga practitioner for more than 30 years had sought to bring this health benefit to people through modern yet simple, affordable technology. In the latest study, the patients who synergised their minds and bodies best (based on the brain and muscles signals recorded by SynPhNe) made the most dramatic improvements.
“Training the patients to self-regulate their mind and body increases their confidence to make positive changes in their lives. It also helps therapists better customize rehabilitation routines based on the individual patient’s capabilities and perceptions,” Mr Subhasis added.
The Singapore-MIT Alliance (SMART) and Technology Transfer Office at NTU (NIEO) are assisting the research group with the commercialisation process.
Shift of Language Function to Right Hemisphere Impedes Post-Stroke Aphasia Recovery
In a study designed to differentiate why some stroke patients recover from aphasia and others do not, investigators have found that a compensatory reorganization of language function to right hemispheric brain regions bodes poorly for language recovery. Patients who recovered from aphasia showed a return to normal left-hemispheric language activation patterns. These results, which may open up new rehabilitation strategies, are available in the current issue of Restorative Neurology and Neuroscience.
“Overall, approximately 30% of patients with stroke suffer from various types of aphasia, with this deficit most common in stroke with left middle cerebral artery territory damage. Some of the affected patients recover to a certain degree in the months and years following the stroke. The recovery process is modulated by several known factors, but the degree of the contribution of brain areas unaffected by stroke to the recovery process is less clear,” says lead investigator Jerzy P. Szaflarski, MD, PhD, of the Departments of Neurology at the University of Alabama and University of Cincinnati Academic Health Center.
For the study, 27 right-handed adults who suffered from a left middle cerebral artery infarction at least one year prior to study enrollment were recruited. After language testing, 9 subjects were considered to have normal language ability while 18 were considered aphasic. Patients underwent a battery of language tests as well as a semantic decision/tone decision cognitive task during functional MRI (fMRI) in order to map language function. MRI scans were used to determine stroke volume.
The authors found that linguistic performance was better in those who had stronger left-hemispheric fMRI signals while performance was worse in those who had stronger signal-shifts to the right hemisphere. As expected, they also found a negative association between the size of the stroke and performance on some linguistic tests. Right cerebellar activation was also linked to better post-stroke language ability.
The authors say that while a shift to the non-dominant right hemisphere can restore language function in children who have experienced left-hemispheric injury or stroke, for adults such a shift may impede recovery. For adults, it is the left hemisphere that is necessary for language function preservation and/or recovery.
Brain-imaging tool and stroke risk test help identify cognitive decline early
UCLA researchers have used a brain-imaging tool and stroke risk assessment to identify signs of cognitive decline early on in individuals who don’t yet show symptoms of dementia.
The connection between stroke risk and cognitive decline has been well established by previous research. Individuals with higher stroke risk, as measured by factors like high blood pressure, have traditionally performed worse on tests of memory, attention and abstract reasoning.
The current small study demonstrated that not only stroke risk, but also the burden of plaques and tangles, as measured by a UCLA brain scan, may influence cognitive decline.
The imaging tool used in the study was developed at UCLA and reveals early evidence of amyloid beta “plaques” and neurofibrillary tau “tangles” in the brain — the hallmarks of Alzheimer’s disease.
The study, published in the April issue of the Journal of Alzheimer’s Disease, demonstrates that taking both stroke risk and the burden of plaques and tangles into accout may offer a more powerful assessment of factors determining how people are doing now and will do in the future.
“The findings reinforce the importance of managing stroke risk factors to prevent cognitive decline even before clinical symptoms of dementia appear,” said first author Dr. David Merrill, an assistant clinical professor of psychiatry and biobehavioral sciences at the Semel Institute for Neuroscience and Human Behavior at UCLA.
This is one of the first studies to examine both stroke risk and plaque and tangle levels in the brain in relation to cognitive decline before dementia has even set in, Merrill said.
According to the researchers, the UCLA brain-imaging tool could prove useful in tracking cognitive decline over time and offer additional insight when used with other assessment tools.
For the study, the team assessed 75 people who were healthy or had mild cognitive impairment, a risk factor for the future development of Alzheimer’s. The average age of the participants was 63.
The individuals underwent neuropsychological testing and physical assessments to calculate their stroke risk using the Framingham Stroke Risk Profile, which examines age, gender, smoking status, systolic blood pressure, diabetes, atrial fibrillation (irregular heart rhythm), use of blood pressure medications, and other factors.
In addition, each participant was injected with a chemical marker called FDDNP, which binds to deposits of amyloid beta plaques and neurofibrillary tau tangles in the brain. The researchers then used positron emission tomography (PET) to image the brains of the subjects — a method that enabled them to pinpoint where these abnormal proteins accumulate.
The study found that greater stroke risk was significantly related to lower performance in several cognitive areas, including language, attention, information-processing speed, memory, visual-spatial functioning (e.g., ability to read a map), problem-solving and verbal reasoning.
The researchers also observed that FDDNP binding levels in the brain correlated with participants’ cognitive performance. For example, volunteers who had greater difficulties with problem-solving and language displayed higher levels of the FDDNP marker in areas of their brain that control those cognitive activities.
“Our findings demonstrate that the effects of elevated vascular risk, along with evidence of plaques and tangles, is apparent early on, even before vascular damage has occurred or a diagnosis of dementia has been confirmed,” said the study’s senior author, Dr. Gary Small, director of the UCLA Longevity Center and a professor of psychiatry and biobehavioral sciences who holds the Parlow–Solomon Chair on Aging at UCLA’s Semel Institute.
Researchers found that several individual factors in the stroke assessment stood out as predictors of decline in cognitive function, including age, systolic blood pressure and use of blood pressure–related medications.
Small noted that the next step in the research would be studies with a larger sample size to confirm and expand the findings.
Tests to Predict Heart Problems and Stroke May Be More Useful Predictor of Memory Loss than Dementia Tests
Risk prediction tools that estimate future risk of heart disease and stroke may be more useful predictors of future decline in cognitive abilities, or memory and thinking, than a dementia risk test, according to a new study published in the April 2, 2013, print issue of Neurology®, the medical journal of the American Academy of Neurology.
“This is the first study that compares these risk scores with a dementia risk score to study decline in cognitive abilities 10 years later,” said Sara Kaffashian, PhD, with the French National Institute of Health and Medical Research (INSERM) in Paris, France.
The study involved 7,830 men and women with an average age of 55. Risk of heart disease and stroke (cardiovascular disease) and risk of dementia were calculated for each participant at the beginning of the study. The heart disease risk score included the following risk factors: age, blood pressure, treatment for high blood pressure, high density lipoprotein (HDL) cholesterol, total cholesterol, smoking, and diabetes. The stroke risk score included age, blood pressure, treatment for high blood pressure, diabetes, smoking, history of heart disease, and presence of cardiac arrhythmia (irregular heart beat).
The dementia risk score included age, education, blood pressure, body mass index (BMI), total cholesterol, exercise, and whether a person had the APOE ?4 gene, a gene associated with dementia.
Memory and thinking abilities were measured three times over 10 years.
The study found that all three risk scores predicted 10-year decline in multiple cognitive tests. However, heart disease risk scores showed stronger links with cognitive decline than a dementia risk score. Both heart and stroke risk were associated with decline in all cognitive tests except memory; dementia risk was not linked with decline in memory and verbal fluency.
“Although the dementia and cardiovascular risk scores all predict cognitive decline starting in late middle age, cardiovascular risk scores may have an advantage over the dementia risk score for use in prevention and for targeting changeable risk factors since they are already used by many physicians. The findings also emphasize the importance of risk factors for cardiovascular disease such as high cholesterol and high blood pressure in not only increasing risk of heart disease and stroke but also having a negative impact on cognitive abilities,” said Kaffashian.
Robot-Delivered Speech and Physical Therapy
In one of the earliest experiments using a humanoid robot to deliver speech and physical therapy to a stroke patient, researchers at the University of Massachusetts Amherst saw notable speech and physical therapy gains and significant improvement in quality of life.
Regarding the overall outcome, speech language pathologist and study leader Yu-kyong Choe says, “It’s clear from our study of a 72-year-old male stroke client that a personal humanoid robot can help people recover by delivering therapy such as word-retrieval games and arm movement tasks in an enjoyable and engaging way.”
A major focus of this case study was to assess how therapy interventions in one domain, speech, affected interventions in another, physical therapy, in two different delivery scenarios. Despite the importance of working with other professionals, the authors point out, until now it has been “largely unknown how interventions by one type of therapy affects progress in others.”
The client, with aphasia and physical disability on one side, completed a robot-mediated program of only speech therapy for five weeks followed by only physical therapy for five weeks in the sole condition, but for the sequential condition he attended back-to-back speech and physical therapy sessions for five weeks.
Over the course of the experiment, the client made “notable gains in the frequency and range of the upper-limb movements,” the authors say. He also made positive gains in verbal expression. Interestingly, his improvements in speech and physical function were much greater when he engaged in only one therapy than when the two therapies were paired in sessions immediately following each other. The authors summarize that in such a sequential schedule “speech and physical functions seemed to compete for limited resources” in the brain. Their work is described in the current issue of the journal Aphasiology.
Choe and computer science researcher and robot expert Rod Grupen, director of the Laboratory for Perceptual Robotics at UMass Amherst, are in the second year of a $109,251 grant from the American Heart Association to investigate the effect of stroke rehabilitation delivered by a humanoid robot, uBot-5. It is a child-sized unit with arms and a computer screen through which therapists interact with the client.
Choe, Grupen and colleagues are seeking ways to bring more and longer-term therapy and social contact to people recovering from stroke. It’s estimated that 3 million Americans daily experience the debilitating effects of stroke. But even after years, they can recover significant function with intensive rehabilitation, says Choe. The bad news is that this is rarely available or accessible due to a shortage of therapists and lack of coverage for long-term treatment. Many people are left with chronic low function, which can lead to social isolation and depression.
While some may object to robots delivering therapy, the need is great and definitely not being met now, especially in rural areas, Grupen and Choe point out. They hope to aid human-to-human interaction, so a robot can temporarily take the therapist’s place. Grupen says, “In addition to improving quality of life, if we can support a client in the home so they can delay institutionalization, we can improve outcomes and make a huge impact on the cost of elder care. There are 70 million baby boomers beginning to retire now.”
“Stroke rehabilitation is such a monumental financial problem everywhere in the world, that’s where it can pay for itself,” he adds. “A personal robot could save billions of dollars in elder care while letting people stay in their own homes and communities. We’re hoping for a win-win where our elders live better, more independent and productive lives and our overtaxed healthcare resources are used more effectively.”
Astrocyte Signaling Sheds Light on Stroke Research
New research published in The Journal of Neuroscience suggests that modifying signals sent by astrocytes, our star-shaped brain cells, may help to limit the spread of damage after an ischemic brain stroke. The study in mice, by neuroscientists at Tufts University School of Medicine, determined that astrocytes play a critical role in the spread of damage following stroke.
The National Heart Foundation reports that ischemic strokes account for 87% of strokes in the United States. Ischemic strokes are caused by a blood clot that forms and travels to the brain, preventing the flow of blood and oxygen.
Even when blood and oxygen flow is restored, however, neurotransmitter processes in the brain continue to overcompensate for the lack of oxygen, causing brain cells to be damaged. The damage to brain cells often leads to health complications including visual impairment, memory loss, clumsiness, moodiness, and partial or total paralysis.
Research and drug trials have focused primarily on therapies affecting neurons to limit brain cell damage. Phil Haydon’s group at Tufts University School of Medicine have focused on astrocytes, a lesser known type of brain cell, as an alternative path to understanding and treating diseases affecting brain cells.
In animal models, his research team has shown that astrocytes—which outnumber neurons by ten to one—send signals to neurons that can spread the damage caused by strokes. The current study determines that decreasing astrocyte signals limits damage caused by stroke by regulating the neurotransmitter pathways after an ischemic stroke.
The research team compared two sets of mice: a control group with normal astrocyte signaling levels and a group whose signaling was weakened enough to be made protective rather than destructive. To assess the effect of astrocyte protection after ischemic strokes, motor skills, involving tasks such as walking and picking up food, were tested. In addition, tissue samples were taken from both groups and compared.
“Mice with altered astrocyte signaling had limited damage after the stroke,” said first author Dustin Hines, Ph.D., a post-doctoral fellow in the department of neuroscience at Tufts University School of Medicine. “Manipulating the astrocyte signaling demonstrates that astrocytes are critical to understanding the spread of damage following stroke.”
“Looking into ways to utilize and enhance the astrocyte’s protective properties in order to limit damage is a promising avenue in stroke research,” said senior author Phillip Haydon, Ph.D. Haydon is the Annetta and Gustav Grisard professor and chair of the department of neuroscience at Tufts University School of Medicine and a member of the neuroscience program faculty at the Sackler School of Graduate Biomedical Sciences at Tufts.
(Source: now.tufts.edu)
Gets stroke patients back on their feet
A robot is now being built to help stroke patients with training, motivation and walking.
In Europe, strokes are the most common cause of physical disability among the elderly. This often result in paralysis of one side of the body, and many patients suffer much reduced physical mobility and are often unable to walk on their own. These are the hard facts the EU project CORBYS has taken seriously. Researchers in six countries are currently developing a robotic system designed to help stroke patients re-train their bodies. The concept is based on helping the patient by constructing a system consisting of powered orthosis to help patient in moving his/her legs and a mobile platform providing patient mobility.
The CORBYS researchers are also working with the cognitive aspects. The aim is to enable the robot to interpret data from the patient and adapt the training programme to his or her capabilities and intention. This will bring rehabilitation robots to the next level.
Back to walking normally
It is vital to get stroke patients up on their feet as soon as possible. They must have frequent training exercises, and re-learn how to walk so that they can function as good as possible on their own.
Why a robot? “Absolutely, because it is difficult to meet these requirements using today’s work-intensive manual method where two therapists assisting the patient by lifting one leg after the other”, says ICT researcher Anders Liverud at SINTEF, which is one of the CORBYS project partners.
Robot-patient learning
CORBYS involves the use of physiological data such as heart rate, temperature and muscle activity measurements to provide feedback to the therapist and help control the robot. Do the patient’s legs always go where the patient want? Is the patient getting tired and stressed?
“The walking robot has several settings, and the therapist selects the correct mode based on how far the patient has come in his or her rehabilitation”, says Liverud. “The first step is to attach sensors to the patient’s body and let them walk on a treadmill. A therapist manually corrects the walking pattern and, with the help of the sensors, create a model of the patient’s walking pattern”, he says.
In the next mode, the system adjusts the walking pattern to the defined model. New adjustments are made and are used to improve optimisation of the walking pattern.
“The patient wears an EEG cap which measures brain activity”, says Liverud. “By using these signals combined with input from other physiological and system sensors, the robotic system registers whether the patient wants to stop, change speed or turn, and can adapt immediately”, he says. “The robot continues to correct any walking pattern errors. However, since it also allows the patient the freedom to decide where and how he or she walks, the patient experiences control and keeps motivation to continue with the training”, says Liverud.
Working with Europe
The European researchers have now completed specification of the system and its components, and construction of the robot is underway.
Construction involves a large team. The University of Bremen is heading the project and developing the architecture to integrate all system modules, and German wheelchair, orthosis and robotics experts are constructing the mechanical components, while two UK universities are working with cognitive aspects. Spanish specialists are addressing brain activity measurements and the University of Brussels is looking into robot control. SINTEF is working with the sensors and the final functional integration of the system. In a year’s time construction will be completed and the robot will be tested on stroke patients at rehabilitation institutes in Slovenia and Germany. The CORBYS project has a total budget of EUR 8.7 million.
