New research on mini strokes points to earlier diagnosis, prevention

Research by Prof Gary Turner and others offers new insights into mini strokes that could lead to prevention, earlier diagnoses and improved health outcomes of Ontarians.

York psychology Professor Gary Turner realizes the perks of working at a global centre of excellence in cognitive neuroscience and neurorehabilitation – primarily, the opportunities to work in a leadership position with other high-profile Canadian researchers. He recently undertook a systematic review, which collects and analyzes multiple research studies or papers, with colleagues from the University of Toronto, the Rotman Research Institute at Baycrest, and Sunnybrook Health Sciences Centre. Turner has been supervising lead author and graduate student, Ayan Dey.

Gary Turner

Gary Turner

What this team learned about mini (or silent) strokes could lead to improved prevention through policy uptake and earlier diagnoses combined with appropriate treatment plans. Through this research, funded by the Canadian Institutes of Health Research (CIHR) and the Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, Turner sees a very real potential for improved health outcomes of Ontarians.

In this Q&A, Turner explains the key findings of this systematic review published in Alzheimer’s & Dementia (2016). He also reflects on what this collaboration says about the caliber of York’s Psychology Department, ranked one of the top programs in Canada, according to Maclean’s 2016 Program Rankings, and in the world according to the QS World University Rankings, 2016.

“York is playing an increasingly important role because we have the talent, and we now have the Vision Research Centre and the Neuroimaging Centre.” – Gary Turner

Q. What were the goals of this systematic review?

A. For context, cerebral small vessel disease is a breaking down of the brain’s vascular system. This happens to all of us as we age. But larger changes to this system can cause cognitive problems. What happens with small vessel disease is that the smallest arteries in the brain become more rigid or brittle and as such, they may be more profoundly affected by normal changes that occur throughout our daily lives, such as changes in blood pressure.

The brain’s vascular system

The brain’s vascular system

This often affects the white matter of the brain, which is the brain’s communications or wiring, whereas large-vessel strokes often result in damage to the grey matter, where the neural processing occurs.

So what happens is the small vessels become blocked or rupture, which we can see in our imaging as bleeds or inflammation.

What we’re talking about are mini or silent strokes. When you mix these mini strokes with Alzheimer’s disease, which affects memory and typically starts in a specific part of the brain called the temporal lobes, you often see [a] more rapid cognitive decline. And we’re finding now that Alzheimer’s disease is almost always mixed with this form of small vessel disease or mini strokes. When this happens, the rates of dementia are much higher. The higher functions of the brain, like planning and decision-making, are likely to be affected.

What this paper asks is how do these changes in the vascular health of the brain impact cognitive functioning? Answering this question was the primary goal.

Q: How did you go about the review of the literature?

A: To identify relevant studies for our primary question, from 2014 to 2015, we looked through large databases of studies, with search terms such as vascular cognitive impairment, and we added on terms related to neuroimaging. Through this, we gathered up almost 500 studies that were ultimately filtered down to 47.

“At York, we’ve built up vision neuroscience, cognitive neuroscience and neurobiology to be absolute core nodes of this engine of Toronto’s world-class research.” – Gary Turner

Q. How does this research add to existing literature and further our understanding of brain functionality?

A. How has this been studied in the past has been in terms of the number of mini strokes – asking: Does the number of strokes predict cognitive deficit? It turns out we can’t do this very well; this correlation isn’t very strong. A person can remain cognitively intact even after many mini strokes.

White matter lesions

White matter lesions

There’s a big piece in how we’ve approached this before that’s missing, and that is discovering how these mini strokes affect brain function – or the brain “at work.” We were interested in seeing how these types of changes impact brain function, and how that would relate to cognitive impairment.

The importance of this work is, I believe, to realize how changes in the wiring are altering brain function, and what that can tell us about cognitive changes, including diagnosing mild cognitive impairment or dementia.

If we understand how these mini strokes disrupt brain function, resulting in specific cognitive changes, it will help us to diagnosis and, ultimately, to treat these changes. Once we’re able to do earlier diagnostics, we’ll be better able to do different, and appropriate, treatment courses. That’s why this work is so applicable or translational, in other words.

Q. What are the implications of this? 

A. Now that we know what’s happening concerning the combination of mini strokes and Alzheimer’s, you take that all the way back to healthy eating, reducing hypertension and increasing physical exercise. These are modifiable factors. It’s really important to understand.

“York is becoming highly recognized. We bring our own expertise to the table.” – Gary Turner

Why people develop Alzheimer’s disease remains to a great extent a mystery, posing a significant challenge for developing treatment or prevention strategies. However, we do know how to help with vascular brain health to avoid or reduce the risk of these mini-strokes. We can change our behaviours, for example, better eating and exercise, throughout our lives.  That gives us an opportunity to focus on prevention.

We’ve got to promote brain health through exercise and nutrition, urges Turner

We’ve got to promote brain health through exercise and nutrition, urges Turner

Q. What does this collaboration say about York’s standing in neuroscience?

A. The GTA is now one of the leading hubs of neuroscience, a meeting centre for world-class research. We have an abundance of resources, expertise, talent and innovation.

York is playing an increasingly important role in this because we have the talent, and we now have the Vision Research Centre and the Neuroimaging Centre. At York, we’ve built up vision neuroscience, cognitive neuroscience and neurobiology to be absolute core nodes of this engine of Toronto’s world-class research; York is becoming highly recognized as a vital node in this very impressive engine of discovery here in the GTA.

Q. What can you say about the importance of funding this kind of research?

A. Funding this type of research is essential. It’s going to help people. With this new knowledge, we have a new route in. We’ve got to promote brain health through exercise, through nutrition. If you don’t look after the plumbing, then you’re going to change how the brain works… and that’s going to manifest as cognitive problems. This research has real policy implications for the overall health outcomes of Ontarians.

The article, “Pathoconnectomics of cognitive impairment in small vessel disease: A systematic review,” was published in Alzheimer’s & Dementia (2016). For more information on Turner’ work, visit his profile and the Cognitive Neuroscience & Neuro-intervention Lab website.

By Megan Mueller, manager, research communications, Office of the Vice-President Research & Innovation, York University, muellerm@yorku.ca