Wat is er al bekend over long covid en de hersenen?

Short answer

There are likely several ways in which COVID can lead to long-term symptoms. One possibility is that in people with long COVID, the immune system remains active much longer than necessary to fight off the virus. This prolonged immune response can reach the brain and cause damage to brain cells and their connections. Additionally, changes in cellular energy production might also play a role. Together, these factors may contribute to symptoms like brain fog, concentration issues, and/or fatigue.

Longer answer

Inflammation in the brain

When a virus enters the body, the immune system activates to fight off the virus as quickly as possible, triggering an inflammatory response. Various inflammatory substances are released into the bloodstream, which also affect the brain. This is why you often feel tired when sick; it helps conserve energy to fight the virus. Once the virus is defeated, the level of inflammatory substances typically drops, and we begin to feel better.

However, in the case of COVID, it seems that inflammation does not subside in everyone. This inflammation can last for weeks or even months, having a long-lasting impact on the brain. Specific immune cells in the brain, called microglia, become activated. This process requires a lot of energy and releases substances that may cause brain damage. For example, it can lead to the death of cells in the hippocampus, the brain’s memory centre, which likely contributes to memory problems.

Moreover, myelin, a substance that insulates brain connections, also breaks down. This weakens or damages the connections between brain cells. You can think of this as a damaged telephone cable: it makes it harder for brain areas to communicate with each other, leading to symptoms such as brain fog and concentration issues.

Image: Example of brain inflammation in an individual with long COVID (top two images), compared to a healthy person (bottom images). The images show cross-sections measured with PET scans. The more red and yellow the image, the greater the level of inflammation in that area.

The cell’s energy centres are damaged

The exact cause of fatigue seen in long COVID remains unclear. It may be because inflammation consumes a lot of energy, but it could also be due to disruptions in the cells’ energy processes. There is evidence suggesting that the ‘powerhouses’ of the cell, called mitochondria, do not function as well in people with chronic fatigue. These mitochondria are responsible for converting oxygen into energy, so when they are impaired, less energy is available to the body, which may lead to feelings of fatigue.

Additionally, other mechanisms may contribute to long COVID symptoms. For instance, COVID has been linked to the formation of small blood clots, which can cause mini-strokes. These mini-strokes are often so small that they may not be immediately noticeable, but they can still affect the brain’s overall functioning.

Why does it affect some people and not others?

Unfortunately, much is still unknown about the causes of long COVID. It is unclear, for example, why some individuals develop prolonged inflammation after COVID while others do not. However, evidence suggests that women, for instance, may be at higher risk. Additionally, factors such as smoking, older age, and pre-existing psychiatric conditions also seem to increase the likelihood of developing long COVID. The exact reasons for these increased risks, however, remain uncertain.

There is also some positive news. Many people eventually recover, and more than 50 studies are currently underway to find a medication that could speed up recovery from long COVID. Researchers are also looking into whether insights from other conditions associated with fatigue, such as post-cancer fatigue or Lyme disease, could help in understanding and treating long COVID. Hopefully, these efforts will lead to more clarity and effective treatment in the near future.

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