When blood flow in the brain is restricted

Vascular dementia is an umbrella term for diseases in which the function of the brain is impaired. The term "vascular" is derived from the Latin word "vas" for "vessel" and means "affecting the blood vessels." The common cause of these diseases is a change in the blood flow to the brain: if it is restricted, the nerve cells in the brain can no longer work as usual and suffer permanent damage, which can lead to memory loss and concentration problems, among others. While Alzheimer's dementia, for example, is initially manifested in most patients by a disturbance in spatial memory and they can, for example, no longer find their way home, the first symptoms of vascular dementias include a general slowing down, concentration problems and also an unsteady gait.

Vascular dementias can be divided into three main subcategories. First, the dementia that can occur after an acute stroke; second, the so-called cerebral microangiopathies that often build up unnoticed over decades; and third, the vascular component in other dementias such as Alzheimer's disease.

One of the most common types of vascular dementia is that which occurs after an acute stroke. Nerve cells can be damaged by the blood clot that has formed in the brain, leaving patients with permanent limitations in brain function. Such limitations occur after up to 30 percent of strokes; often weeks or even months after the stroke. With around 300,000 strokes occurring in Germany alone each year, this results in a high number of people affected. Often, treating physicians recognize this complication early on, so that occupational therapists, speech therapists and neuropsychologists can begin therapies based on further testing - from motor and speech exercises to light memory training.

Cerebral microangiopathies develop insidiously. Over years and decades, small blood vessels in the brain - often microscopic vessels - narrow, so that patients initially do not notice any limitations. The first constrictions may occur at the age of 40, but they do not show noticeable consequences until after the age of 60. At this late stage, therapy is then difficult because much damage has already occurred. In 70 to 80 percent of cases, cerebral microangiopathy is actually diagnosed at this late stage; in the remaining cases, doctors come across the incipient problems beforehand through an incidental finding - for example, when they perform a magnetic resonance imaging (MRI) scan because of persistent migraines or other complaints unrelated to dementia.

The risk of microangiopathies, which account for about 20-30 percent of all dementia cases, can be reduced through targeted prevention. The same advice applies here as for other vascular diseases: Endurance sports and a healthy diet are among the preventive tools, while obesity, smoking, diabetes and high blood pressure are among the risk factors. Even after the first symptoms appear, patients can slow down the progression of memory loss if they pay attention to a healthy lifestyle. However, it is currently not possible to cure the damage that has already occurred.

In extremely rare cases, cerebral microangiopathies also have genetic causes. In these cases, abnormalities often occur in patients between the ages of 30 and 40.

Researchers are now convinced that vascular changes - i.e. problems with blood flow to the brain - also play a role in Alzheimer's dementia. Alzheimer's patients have 20 percent less blood flow to the brain. Whether this is one of the causes of the disease or a consequence is still being investigated.

Hopes for a future therapy of vascular dementia are currently focused, among other things, on the so-called astrocytes. They are located in the brain directly next to the nerve cells and enter into a regular symbiosis with them: They supply them with everything they need. In a sense, they know how to keep nerve cells alive. It is hoped that once researchers have a better understanding of how these astrocytes work, they will be able to generate clues as to how the nerve cells can be influenced and stimulated. In addition, scientists are testing the use of already approved drugs to slow down the damage caused by circulatory disorders in the brains of patients or even to repair it in the long term.

To gain deeper insights into the mechanisms of vascular dementia, researchers at the DZNE have launched a large clinical trial, among others. It is called DEMDAS (DZNE - Mechanisms of Dementia after Stroke). 600 patients at the sites in Berlin, Bonn, Göttingen, Magdeburg and Munich are being monitored and intensively examined over several years. .