Tiredness, coughing or pneumonia are typical symptoms of Covid 19 disease. But they are far from the only ones. While some people have little discomfort and do not even notice their illness, others experience a heart attack, the next lose their sense of smell and still others cannot breathe without help.
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Experts do not yet know exactly why. But they’re looking for answers everywhere. And because different systems interact in the human body, not only virologists and immunologists collect their patients’ data in order to learn as much as possible about the new virus. Cardiac specialists, intensive care physicians, pathologists, radiologists, pediatricians, general practitioners and ENT specialists are also in demand. And neurologists. Because the virus does not stop at our nervous system.
Odor disorders, strokes, epileptic seizures, paralysis, headaches – there are now a whole series of observations that show that infection with Sars-CoV-2 can also affect the central nervous system. In a study from China of 214 patients, 78 of them (36 percent) had different neurological complaints.
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At first, this is not particularly worrying because many infections include headache, dizziness, and nausea as a result of general weakness or circulatory problems. However, Sars-CoV-2 can sometimes go one step further: Of the 78 patients from Wuhan with neurological symptoms, 13 had impaired consciousness, five had a stroke and one had an epileptic attack. The doctors suspect that the viruses could sometimes directly affect the nerve cells.
Meningitis
A case report confirms this assumption: a 24-year-old man from Japan only felt dull and tired for over a week, had a headache and felt dizzy. Because his doctor suspected flu, he prescribed an influenza medicine that did not help. On the ninth day, the man developed an epileptic seizure and had to be taken to the hospital as an emergency. There the doctors discovered inflammation of his meninges and brain and mild viral pneumonia. The coronavirus smear in the throat, however, was negative.
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To find out which pathogen triggered the severe inflammation of the brain, doctors at the University of Yamanashi examined the nerve water that washes around the spinal cord and brain. They found both inflammatory cells and Sars-CoV-2. “We already knew from Sars and Mers that the pathogens can directly affect the spinal cord and brain,” said Peter Berlit, general secretary of the German Society for Neurology, SPIEGEL. “Now we are sure about Sars-CoV-2 too.”
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The olfactory disorder
How the pathogens make their way into the brain is still unclear. “Spread through the blood system is conceivable,” says Berlit. “Most likely, however, is that the infection occurs via the olfactory tract.” This is supported by the fact that a large number of patients complain of malodour: in a study conducted by the Belgian University of Mons with 417 people with mild Sars-CoV-2 infections, the figure was 86 percent. Not everyone had a stuffy nose, which could restrict their sense of smell. A study in Italy came to the conclusion that 64 percent of the patients with mild Covid 19 symptoms also reported having olfactory disorders.
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The olfactory tract is directly connected to the forehead, so that the viruses can spread neuron quickly here. In order to better understand how Sars-CoV-2 affects the sense of smell and taste, scientists from 42 countries have joined together in the Global Consortium for Chemosensory Research. The research community plans to publish the first results shortly.
In addition to the olfactory tract, a further entry gate could also be so-called peripheral nerves such as the vagus nerve, which among other things controls lung and heart activity. This important nerve receives its signals from the brain stem, one of the most important nodes in our nervous system, which lies between the cerebrum and spinal cord. Many vital functions are controlled in a small space: the heart rate, for example, blood pressure, reflexes – and breathing.
The respiratory failure
It is noticeably often that doctors in their Covid 19 patients observe that they suddenly become short of breath and their condition worsens massively, sometimes even without previous lung symptoms. This rapid change can only partially explain that the viruses cause severe inflammation in the lungs. “A possible cause could be a disturbance in the respiratory center due to brain stem involvement, as described in Sars,” said Berlit.
The problem with researching this theory is that here too, reliable data is still lacking. Not all of the deceased are autopsied, so that pathologists can subsequently understand the pathological processes in the brain. And in order to examine the brain functions in sick people closely, the patients would have to be examined in magnetic resonance, which in turn means a logistical hurdle in the intensive care units claimed. After all, ventilation and intensive care treatment come first, and the patient must be isolated because of the infection.
The stroke
Like many other physicians, neurologists are hoping for answers to the many unanswered questions from the newly created European registry, Leoss, in which clinical data from patients with Sars-CoV-2 infection are collected.
It is also unclear why some Covid 19 patients with violent courses also develop strokes, as the Chinese research group describes, among other things. A stroke is always the result of poor circulation or bleeding in the brain. Since the coagulation system is often activated to counteract a severe infection, Sars-CoV-2 could “promote strokes”, says Götz Thomalla from the University Medical Center Hamburg-Eppendorf.
But a direct inflammatory reaction in the arteries could also be responsible for strokes, specialists suspect. The corona virus apparently has a high affinity for a receptor called AT2, which is located in the vessel walls. “To be honest, we just don’t know where this cluster comes from,” says Peter Berlit. “Because, of course, many people with severe Covid-19 courses have pre-existing conditions such as diabetes and high blood pressure, which significantly increased the risk of a stroke. They were also all severely lung-affected and suffered from a lack of oxygen and an increased tendency to clot, which also favors a stroke certain medications. “
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The rising paralysis
Observations of an old clinical picture, which doctors from Italy and Wuhan now describe for the first time in Covid 19 patients, are brand new. In Italy, four sufferers developed leg paralysis related to Sars CoV-2 infection, and a fifth had facial muscles paralyzed. A patient from Wuhan was also initially unable to move her legs and later was unable to breathe alone.
The so-called Guillain-Barré syndrome is already known from other infectious diseases with Zika or cytomegaloviruses or bacteria such as Campylobacter. The antibodies that the immune system has formed due to the infection against the pathogen are directed against the body’s own tissue in the nerve sheaths. This usually leads to inflammation of the peripheral nerves and paralysis, which often begins on the legs and can rise to the respiratory muscles, a few weeks after the acute infection. Most of the patients slowly reverse their paralysis in reverse order.
In all six cases from Italy and Wuhan described, the doctors had detected Sars-CoV-2 in the patient’s body. It is still unclear whether the virus was the cause of Guillain-Barré syndrome or coincidentally. The patient from Wuhan received antiviral agents, the patients in Italy received infusions with antibodies, as do other Guillain-Barré syndrome patients. According to the case report, the Chinese patient is now completely healthy again, one of the Italian patients could also be discharged from the clinic, two of them still have paralysis and two others still have to be ventilated.
The conclusion
Even if we are still at the beginning of the pandemic: Because Covid-19 behaves like a chameleon, as Swiss researchers called it, general practitioners and internists have to remember that headache, dizziness or malodour disorders may also be due to an infection with coronaviruses . “And we neurologists also have to take into account serious symptoms such as meningitis,” says Berlit, “that Sars-CoV-2 could have triggered this.”
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