Research Profile – Picturing Dementia

A 'real world' brain study leads to a new understanding of dementia and improved diagnosis.

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A long-term brain imaging project is helping clinicians make treatment decisions relating to dementia, and at the same time is changing our understanding of these brain diseases.

Since 1995, as part of the Sunnybrook Dementia Study, high quality brain scans of over 1,000 patients have been collected, along with scans of 150 healthy control brains for comparison. The patients have various types of dementia, including Alzheimer's, vascular dementia, frontal temporal dementia, Parkinson's disease and more.

The Sunnybrook population differs from that in other studies because it includes people with mixtures of different dementias, not just people with 'pure' disease – as is often required for drug trials, according to Dr. Sandra Black, the Brain Sciences program research director at Sunnybrook Research Institute.

"The approach in this study gives insight into the real world of dementia," she says.

When people come in for initial assessment, they receive a scan to help with diagnosis and disease management. These clinical scans are saved, undergo computer analysis and are used later to see how a patient's brain has changed over time. Additional scans may be done at other times.

"Studying how the brain changes over time, in combination with annual cognitive testing, is adding significant knowledge about how different types of dementias progress. We can describe disorders much more precisely," says Dr. Black.

Two types of brain scans are performed: MRI and Single-Photon Emission Computerized Tomography (SPECT). MRI scans provide 3D details that are used for measurement of the brain's grey and white matter, blood vessels and patterns of shrinkage.

In addition, Dr. Black's team developed new ways to measure blood flow to specific parts of the brain using SPECT. The research team also performs brain autopsies (so far, this has been done in 150 patients), and collects genetic data.

One area of focus for Dr. Black's team is the white matter, tissue that provides fast and efficient communication between the different brain areas. Small blood vessels throughout white matter play a more important role in dementia than previously thought.

When focusing on the role tiny arteries and veins play in removing amyloid – a toxic protein that accumulates in the brains of Alzheimer's patients – the researchers discovered that small vessel disease, which increases with age, is actually common in dementia. It appears that scarring of the vessel walls can lead to partial or complete blockages, prevent the removal of amyloid and cause leakage of fluids from the veins deep in the brain, leading to further injury.

"Managing vascular risk factors such as hypertension throughout life, along with good lifestyle choices such as not smoking, a heart-healthy diet and exercising are important strategies to delay and reduce the impact of these disabling diseases," says Dr. Black.

Thickening of vessel walls may actually underlie white matter disease and can "impair the ability to clear amyloid from the brain. That venous insufficiency may be the cause of white matter disease is an important finding – it could be one reason that aging is so strongly associated with dementia," she says.

The study, which was funded by the Canadian Institutes of Health Research, also found that a wide variety of symptoms bring Alzheimer's patients to the doctor. They may have problems such as navigating or finding words; it's not all just memory loss. The research also shows that many patients may have more than one disorder causing their dementia.

"Dementia is often due to mixed, not single diseases," says Dr. Black.

"Studying how the brain changes over time, in combination with annual cognitive testing, is adding significant knowledge about how different types of dementias progress. We can describe disorders much more precisely."
– Dr. Sandra Black, Sunnybrook Research Institute

International Collaborative Research Strategy for Alzheimer's Disease