Micro-strokes may be associated with the development of dementia

Anna Stavina, XX2 century

A micro stroke is a type of stroke that lasts only a few minutes. A new study has found that micro-strokes are much more dangerous than is commonly believed.

Stroke is one of the main causes of disability and death in the world. A transient ischemic attack (TIA), or, as it is also called, a "micro stroke" happens when the artery supplying the brain with blood is briefly blocked by a blood clot, a blood clot. A micro stroke is practically the same as a normal stroke, the only difference is in its duration in time.

Existing studies show that approximately 25-30% of people who have suffered an ischemic stroke may develop delayed cognitive impairment of vascular genesis or vascular dementia. Micro-strokes lead to the appearance of tiny lesions 0.05-3 mm in diameter. However, an increasing number of studies indicate a link between micro-strokes and cognitive decline and dementia.

After studying the results of the available work, a group of researchers from the Medical University of South Carolina (Medical University of South Carolina) suggested that micro-strokes can affect brain function to a greater extent than it can be observed on histological preparations or magnetic resonance imaging.

The group of scientists was headed by Associate Professor of Neuroscience Andy Shih. The results of the work were published in the Journal of Cerebral Blood Flow & Metabolism (Summers et al., Functional deficiencies induced by cortical microinfarcts).

Researchers have developed a model of the disease in such a way as to be able to study the effect of individual micro-strokes on the tissues of the cerebral cortex for several weeks after circulatory disorders. Mice were used as model animals.

The scientists applied the photothrombosis method, an experimental technique developed in 1985 to simulate strokes in rats. When using photothrombosis, one arteriole (small artery) in the so-called "columnar cortex" is blocked. This part of the rodent brain is associated with vibrissae on the animal's muzzle.

During the first experiment, the researchers implanted special "cranial windows" in animals, and then began studying brain activity in the area of micro-stroke.

Scientists conducted both in-life and postmortem studies of animal brains.

Postmortem examination of animal brain tissues revealed that a micro-stroke affects a part of the brain that is 12 times larger in volume than the core of the stroke itself. In addition, it was found that the activity of neurons in the area affected by a micro-stroke decreased by 14-17 days.

The authors of the work themselves called its results "unexpected".

"I know that extensive strokes lead to the development of long-term consequences. But I was surprised when it was discovered that such minor damage can produce such a serious effect. On the MRI, the image changed, and then returned to normal, as we expected. But during the examination of the autopsy material, we found that the disease continued to develop – there were signs of brain tissue damage and inflammation in the samples. Even after three weeks, the disturbed blood flow was only partially restored. This means that a micro-stroke can "come and go", only appearing on tomograms for a short time. However, its effect on brain function can persist for a long time, perhaps for months," Shih said.

Shih explained the importance of the work carried out both for assessing the consequences of micro-strokes and for possible practical application in preventive medicine: "These heart attacks are so tiny and unpredictable that we simply do not have the tools to detect them while a person is still alive. So far, we have only had postmortem images taken at the end of a person's struggle with dementia. And also the results of measuring cognitive functions, showing that the deterioration began, perhaps decades before the patient's brain became available for study."

As a rule, micro-strokes are difficult to diagnose using conventional neuroimaging techniques. And the information received during life about the state of the patient's brain often does not coincide with the results of a post-mortem examination. All this makes it difficult to determine the relationship between micro-strokes and the gradual deterioration of cognitive functions.

A study conducted by Shih and colleagues circumvented these limitations. Scientists have created a model that allowed them to observe the consequences of individual micro-strokes for several weeks.

Shih also believes that the discoveries made during the study may change approaches to the prevention of micro-strokes in the future. If one micro-stroke can have a lasting effect on a large area of the brain, then several such events can be considered as the equivalent of a normal stroke. The author adds: "At the clinical level, drugs may begin to play a big role. Maybe the drugs that we already have at our disposal are able to reduce the overall harm from a series of micro-strokes. And maybe such funds will appear in the future."

Portal "Eternal youth" http://vechnayamolodost.ru  19.01.2017