Most people know about stroke a medical emergency which occurs when a major blood vessel in the brain is blocked or breaks, causing massive brain damage. This type of stroke produces obvious or overt symptoms such as paralysis or weakness of limbs, loss of vision or speech. Far less well known and far more common are covert strokes, tiny strokes which unlike overt stroke do not cause obvious impairments.
Covert stroke occurs when small blood vessels in the brain become blocked, depriving the brain of vital oxygen and nutrients and killing nearby brain tissue. One major study of the elderly found about 28 percent of participants had experienced covert strokes. Accumulated damage from covert strokes can eventually cause serious loss of function, especially cognition (i.e. memory, planning and reasoning)
Identifying covert stroke survivors
Covert strokes do not cause obvious motor or sensory symptoms so how do we know who has had one? Thanks to advances in neuroimaging, we can now see accumulated damage from covert stroke using a neuroimaging technique known as magnetic resonance imaging (MRI). We can also detect problems with memory and planning often seen in covert stroke using sensitive cognitive tests.
Damage from a related disorder known as white matter disease, can also been seen using MRI imaging. In white matter disease, the small veins that channel blood back from the brain to the body start to age and narrow. Eventually this damages nearby brain tissue. White matter disease is associated with an increase in the risk of covert stroke and dementia. It also seems to slow down information processing and interfere with the transfer of information within the brain.
Is there a relationship between covert stroke and Alzheimer’s disease?
Our researchers are using advanced imaging techniques to look at the brains of healthy elderly people as well as those of individuals with white matter disease, covert stroke or Alzheimer’s disease. Their goal is to link disorders seen with brain imaging to cognitive problems in individuals. This research will help us to understand more about the complex relationships between these diseases and dementia.
CSR researchers are also studying an intervention called Goal Management Training (GMT) which is designed to help covert stroke survivors and people with white matter disease retake control of their lives by improving their ability to plan and concentrate. A CSR research team led by Dr. Brian Levine and his colleagues is studying behavioral changes which take place during GMT. The team is also studying the effects of GMT on participants’ brain activity.
At present, there is no treatment for either covert stroke or white matter disease. However, both are caused by the unhealthy condition of small blood vessels in the brain. This underlines the importance of controlling blood pressure, cholesterol and diabetes. Our research also shows exercise can reduce the risk of these disorders by increasing brain health, and can accelerate recovery. The take away message: in addition to all its other benefits, an active, healthy lifestyle can help protect against covert stroke and dementia