What does COVID-19 do to your brain?

Even after the SARS CoV-2 virus has been suppressed, the immune system is restless.

This is the current theory of what is behind the bizarre, protracted, debilitating neurological symptoms of some COVID-19 patients, such as the commonly reported “brain fog.” A recent paper in the journal Science.

The virus does not cause widespread infections in the brain. Instead, the neurological effects appear to be caused by “friendly fire” — exaggerated or false immune responses, and damage to blood vessels in the brain, according to Dr. Serena Spditch and Dr. Abindranas of the Yale School of Medicine. .. National Institute of Health.

“Immune activation and inflammation within the central nervous system are the major causes of neurological disorders in acute COVID-19,” they write.

Nervous system problems are one of a series of diverse symptoms reported by people with Long COVID, an undefined syndrome that affects 7% to 18% of people after infection. Some appear at the same time as respiratory symptoms. Others appear after 2 weeks on average. However, they can last for months. Vaccinated people are less likely to have a longer COVID. According to some recent studies..

Even young and healthy people with mild early illness can develop these symptoms. These symptoms range from mild headaches in a short period of time to persistent mental fatigue, depression and even psychosis. According to another recent study, “brain fog” is one of the most common problems, affecting about two-thirds of patients in post-COVID clinics in New York. It is unclear if unexpected problems can occur years after the initial infection.

The conclusions are supported by a newly published study at the University of California, San Francisco. The study found that some patients who develop new cognitive symptoms after a mild attack of COVID have cerebrospinal fluid abnormalities similar to those found in people with other infections.

“The virus-stimulated immune system may be functioning in unintended pathological ways,” he said. UCSF Coronavirus Neurocognitive Research..

COVID-19 is not the only one: Other infections have been shown to upset the immune system. For example, multiple sclerosis can be caused by an Epstein-Barr virus infection. Cognitive symptoms have been identified with Epstein-Barr infection, HIV, hepatitis C, coronavirus SARS and MERS.

Indeed, according to Spudich and Nath, it is normal to feel tired when infected.

“Symptoms can appear because we’ve exhausted all our energy in an attempt to get rid of the organism,” said Nath, clinical director of the National Center of Neurology and Neurological Disorders at NIH. “But usually you recover from it, and that’s it.”

He said certain things could go wrong, especially if a very small amount of virus invaded the central nervous system or the brain.

The immune system can mistakenly deploy antibodies in the wrong direction that attack not only the virus, but also our own tissues and organs. Similar phenomena are seen in autoimmune disorders such as lupus.

Something else can happen: the immune system goes into an overactive “all hands on deck” mode. Frustrated if the target antibody does not get rid of the virus, the carpet bombing strategy uses cells called monocytes and macrophages. These cells, an important component of the immune system, are associated with other inflammatory diseases and can cause long-term damage. They were found in the brains of autopsy victims of COVID-19.

Inflammation is the cause behind other COVID-related medical crises. For example, a child can develop a multisystem inflammatory syndrome. In the elderly, sudden inflammation of the lungs, called a “cytokine storm,” can be fatal.

In the brain, “with a small amount of inflammation, you can recover,” Nath said. “But if the inflammation is prolonged, or if the inflammation is quite severe, it can cause permanent damage.”

Signs of inflammation and cell damage raise concerns that infection may accelerate or induce future development of neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease.

The virus can also directly damage the vascular system of the brain. For example, an infection causes a small blood clot in a damaged blood vessel, increasing the risk of stroke. It can also cause leaks, causing blood to penetrate the brain, causing inflammation and cell damage.

In addition, systemic infections can exacerbate and reveal the underlying cognitive problems.