How this virus damages the brain and nerves is still not entirely clear. But as two doctors studying the nervous system, we wanted to find some answers.
Dr. Sanjay Gupta has been a practicing neurosurgeon for the past 20 years and has always been amazed by the body’s excellent ways of protecting the brain. A hard shell of bones, a bath of clear fluid, and a blood-brain barrier that creates checkpoints before certain molecules are even allowed to enter. This is our most important organ and more impenetrable than most. And yet, this virus is still able to penetrate the central nervous system.
And Dr. Minali Nigam is a new resident doctor and decided to pursue neurology, a field that combines mind and body. It seems that small details, such as the ability to raise an eyebrow, can tell you which part of the nervous system is injured. We don̵7;t know so much about the brain, which means a huge potential for the growth of our knowledge.
Coronavirus also affects the brain and nerves
Among the most common neurological symptoms is loss of smell and taste, which may be the first clue that someone has Covid-19.
Other possible symptoms include headache, dizziness, loss of consciousness, weakness, convulsions, paralysis, stroke, and so on.
We know that the virus spreads through particles in the air, so it first enters the body through the nose and mouth. When this happens, the virus may potentially cross the cryptocurrency plate, the bone at the top of the nose, to reach the olfactory bulb, which houses the olfactory nerve and its branches. If the virus damages these nerves, a person can lose their sense of smell. If the virus also directly attacks the taste buds, it can prevent nerve fibers from transmitting signals to the brain and cause a person to lose their sense of taste.
Another hypothesis concerns a protein receptor called the angiotensin-converting enzyme – known as ACE2 – that is found in cells throughout the body in the lungs, kidneys, blood vessels, muscles, nose and mouth. In the nose and mouth, the virus is thought to bind to ACE2 receptors in sensory nerve cells and block these cells, facilitating smell and taste.
ACE2 also helps maintain blood pressure and protects the heart and brain from damage. Its role is to lower the level of a molecule called angiotensin II. If angiotensin II levels build up, blood vessels constrict and reduce blood flow to organs, potentially damaging them.
Here is the most interesting thing that we are beginning to study. Whether it’s the body or the brain, most symptoms don’t seem to come directly from the virus, but rather the body’s excessive immune response to the virus.
For example, stroke.
When the virus binds to ACE2 in blood vessels, it triggers an immune response – sometimes called a cytokine storm. Too much inflammation can impair the body’s coagulation system and form millions of small clots or several large clots. Together with higher levels of vasoconstriction angiotensin II, clots can block blood flow to the brain and lead to stroke.
Some strokes are minor and patients may not be aware that they are suffering. With age, multiple strokes can accumulate and lead to memory loss or lack of attention. Other patients who recover after Covid may show symptoms of their silent strokes, such as depression, anxiety, insomnia or cognitive decline later in life, Fotuhi reports.
Too much inflammation can also destroy the protective wall, known as the blood-brain barrier, and lead to brain swelling, seizures, or the spread of infection.
It is not clear why she developed meningitis. But we know that the meninges are a protective layer around the brain and spinal cord and are rich in blood vessels and ACE inhibitors. Theoretically, if the virus binds to ACE inhibitors in the meninges, it can lead to vascular damage and significant inflammation.
Guillain-Barré syndrome, a nervous disorder that can lead to paralysis, has also been found in some patients with the virus. Here, antibodies formed in response to the virus respond to proteins found on nerves, causing damage.
But it is important to remember that everyone reacts to the virus differently.
“There are people who have a measured reaction to the virus, and their immune system can control it without overreacting,” Fotuhi said.
“Healthy people who are asymptomatic are those who have had enough of an immune response to kill the virus without creating a cytokine storm or blood clots.”
Why it matters
How this happens comes down to two main mechanisms: direct viral invasion of the nervous system or damage from the hyperactive immune system.
Some neurological manifestations, such as confusion or weakness, may also be non-specific complications of critical illness not related to the real virus.
“Neurological involvement seems to be an important feature of this coronavirus,” said Dr. Felicia Chow, an expert on neuroinfectious diseases at the University of California, San Francisco.
Or we may see more neurological complications with Covid simply because there are many more cases of general Covid treatment compared to previous coronavirus outbreaks.
As well as what doctors see with Kovid-19 and strokes.
“What has been reported so far is not really what we usually see with at least certain types of respiratory viruses,” she said. “But it’s hard to say with the still limited information we have. To understand the true neurological strain and the consequences of this pandemic requires a much deeper dive.”
There are no large studies examining the neurological symptoms associated with Kovid, so doctors now treat these symptoms in the same way as for patients who do not have the virus.
But there were small studies with several hundred people. One consistent feature is that patients with risk factors such as high blood pressure, diabetes, and obesity who receive Covid are at greater risk of serious consequences, including neurological complications, than healthy and fit people.
That is why regular exercise, healthy eating, proper sleep and stress reduction are still important during this pandemic. By maintaining an active, healthy lifestyle, patients who end up with the infection can “improve their chances of a faster and better recovery,” Fotuhi said.
For doctors, patients with Covid may not suffer from the typical viral symptoms you expect, such as cough or fever. Some patients who show up at the emergency room show only signs of a stroke. And the symptoms of the brain may be the first and only symptoms for the patient. In certain situations, blood thinners and steroids can be just as important as antiviral drugs.
“Kovid can have many different faces,” Fotukhi said. “It’s important for people to appreciate it.”
And that’s what we’ll keep in mind when we take care of patients.
By covering the pandemic as journalists and caring for Kovid’s patients as doctors, we have learned to think openly. What we think today may change tomorrow, and that’s okay. This is part of the learning process. As our knowledge of the virus continues to grow, we are one step closer to continuing this pandemic.