Since the severe special infectious pneumonia (COVID-19, referred to as new coronary pneumonia) was found in China in December 2019, as of June 2022, more than 500 million people have been infected worldwide, and the death toll has reached 6.3 million. It is still ongoing diffusing[1]。
In addition to respiratory symptoms (such as cough, runny nose, nasal congestion, sore throat, etc.) and systemic symptoms (such as headache, body aches, and fatigue), infected patients also have symptoms.nervous systemsymptoms above. The study reported that regarding one-third of the patients had a sense of smell (Dysomia) or a taste disorder (Dysgeusia)[2]and some patients even developed brain fog with long-term symptoms of the new crown (Long COVID) following recovery[3]sequelae.
How exactly does severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affect our brains? What are the physical and mental effects of long-term symptoms following recovery? Are there any current treatments, and how should we respond?
How does the new crown pneumonia affect our brain nerves?
“The Art of War. It is said: “Those who know the enemy and know themselves well will not be imperiled in a hundred battles. In the face of the virus enemy, if humans want to defeat it, they must understand it.
The three elements of an infectious disease are the pathogen, the route of infection, and the host. Among them, the mode of transmission is extremely important. Because as long as we can block the way the virus enters the human body, it is equivalent to destroying the possibility of the enemy’s attack to the main business, giving us more time to prepare weapons (antibodies, vaccines) to fight the enemy (virus).
The transmission route of new coronary pneumonia is still not completely clear, but it is known that type 2 new coronavirus is mainly transmitted through direct inhalation of droplets from a patient’s cough or sneeze, or following touching a surface contaminated with droplets and then touching it. into the body through the eyes, nose or mouth of the face.
The virus then penetrates the Angiotensin-converting enzyme 2 (ACE2) receptor on the cell membrane, enters the cell and replicates in large numbers[4]. The lungs are the primary target of the virus, so patients with severe COVID-19 will develop acute respiratory distress syndrome (ARDS), and they may also have the sequelae of pulmonary fibrosis following subsequent recovery.
In addition, Nasal epithelial cells (NECs), especially the supporting cells (Sustentacular cells) that support olfactory sensing cells (Odor-sensing neurons), also have ACE2 [5].Follow-up biologist Starvros Lomvardas of Columbia University found that the nuclear structure of olfactory neurons had been destroyed by observing patients who died of new coronary pneumonia, which may also explain why most patients lose their sense of smell.[6]。
In addition to loss of smell, some patients also claim to have developedParasmia (Parosmia)Symptoms of diapers and toilet paper turned out to be pleasant.The cause of olfactory inversion is currently unknown, but it is speculated that it may be related to the dislocation of reconnection following olfactory nerve damage, or the destruction of olfactory nerve by the immune system.[7]。
Different variants of the new coronavirus seem to have different effects on the olfactory system. About 50% of patients with Alpha have lost their sense of smell and taste since the earliest beginning, Delta is 44%, and now Omicron is only 17%[8]. In the future, further research is needed to know why different variants of the virus have such large differences in the impact of smell.
Is it possible for the new coronavirus to infect nerves?
We know that Covid-19 can cause breathing difficulties, mostly because the virus infects the lungs, but another possible explanation is that the virus enters the brain area that regulates breathing.In addition, new coronary pneumonia can also cause many neurological symptoms, such as stroke, brain inflammation, symptoms of mental illness, changes in brain structure, brain fog (memory and attention loss), etc.[9]。This also makes scientists curious, whether the new coronavirus can directly infect nerves and cause the above symptoms?
from mouse experiments[10]with deceased patients[11]In the study, it has been observed that the type 2 new coronavirus does indeed cross the blood-brain barrier (BBB), infects the nerve cells in the brain, or penetrates into the brain tissue through the mucosa of the nasal cavity.[12]. Such a discovery also means that, in addition to the lung disease caused by the virus’s attack on the lungs,We also need to pay attention to the length of time and severity of the virus’s impact on the cranial nerves.
Recently, the research team of Tracy Fischer, a professor at Tulane University in the United States, conducted research on primate rhesus monkeys (Rhesus macaques, RM) and wild African green monkeys (AGMs). , found cerebral microhemorrhages (Microhemorrhages), cerebral hypoxia (Brain hypoxia), and neuritis (Neuroinflammation) consistent with hypoxic-ischemic injury (Hypoxic-ischemic injury) in virus-infected primates, neuropathy In terms of physics, evidences such as neuron degeneration and apoptosis are seen.These infected lab animals, which did not develop severe respiratory disease, also provided a link between neurological symptoms and the new crown[13]。
In addition, due to the differences in the time points of the emergence of different variants of the virus and the collection of the number of samples is not enough,It is unclear whether different variants of the virus affect the brain to varying degrees. The sequelae caused by the new crown may also become another wave of challenges that people need to face in the post-epidemic era.
How do smell and taste disorders and brain fog affect our lives?
Many reports have described the phenomenon of parasomnia in patients with COVID-19 following recovering. Clare Freer is one of the many patients suffering from paralysis due to the new crown.[14]. , food, cleaning products, alcohol, perfumes that were supposed to be nice scents turned so bad that he mightn’t even kiss his partner anymore. It also caused her quality of life and psychological state to be seriously affected.
Permanent loss of smell also makes people more vulnerable to dangerous situations because of the inability to instantly detect spoiled food and fire.Symptoms of anosmia may also lead to increased risk of dementia[15]。
In addition to the abnormal sense of smell that plagues new crown patients, many studies have also pointed out that patients still have cognitive and attention deficits in the 12th week following infection, which is commonly known as brain fog.Further research by a team from The University of Cambridge and Imperial College London found that the cognitive impairment caused by the new coronavirus is similar to that between the ages of 50 and 70, equivalent to a 10-point drop in IQ[16]。
Current possible treatment methods of Chinese and Western medicine
The COVID-19 pandemic has caused severe psychological stress to many people, and many patients have suffered from depression as a result, so the support of social peers is also very important. Chrissi Kelly founded AbScent[17] hoping to provide correct knowledge and help people with anosmia, regularly hold online meetings, update blogs, and share professional research literature.While many treatments for anosmia are still in the early clinical stages, researchers suggest that the least that can be done now is olfactory training.
Patients will be asked to smell many different strong-smelling substances and try to identify them, and the process of training will help reshape the signaling of the olfactory neural circuit. But this method is only effective in some patients with anosmia, so only regarding one-third of people with anosmia are helped.
Other possible treatments, such as the use of steroids to reduce inflammation, have been found to be less effective than expected in recent studies.A 2021 study found that patients who received both smell training and a nasal steroid (mometasone furoate) improved their sense of smell as much as those who received only smell training[18]. If there is a permanent abnormality in the sense of smell, hope may have to be pinned on an olfactory implant developed by a research team at Virginia Commonwealth University.When the implant is buried in the nose, the sensed odor molecules can send signals to the brain[19]but it is still in the early research stage.
At present, there is still no consensus in Western medicine for the treatment of brain fog, but Chinese medicine has a set of methods.
Chinese medicine believes that the treatment of brain fog must start from the heart, kidney and lung meridians. Since the brain is the home of the primordial spirit, the “Huangdi Neijing” records: “The kidney dominates the bones, generates the marrow, and communicates with the brain”, so the relationship between the brain and the kidney is inseparable. In addition, “The Yellow Emperor’s Classic of Internal Medicine. Su Wen”: “The heart is the official of the king, and the gods come out.” And “The Yellow Emperor’s Internal Classic.” Lingshu Xie Ke chapter also mentioned that “the heart is the master of the five internal organs and the spiritual home.”
This shows that Chinese medicine believes that the “heart” is the commander of the body, so strengthening the heart is especially important in the treatment of brain fog. Many patients with new crown have symptoms of lung qi deficiency, so it is also necessary to improve the lung meridian.In terms of treatment, you can use Chinese herbal medicine Chaihu Jialonggu Muli Decoction, Sini Decoction, Guizhi Decoction and Fuzi Decoction, Kong Shengzhen Zhongdan, and scalp acupuncture to stimulate the brain to unblock the meridians[20]。
keep hope, keep going
In the face of the unprecedented challenge of the epidemic and the sudden separation of life and death, the world’s economy, culture, politics, education, etc. have also been severely hit. While all life is in chaos, many patients also face the disorder of smell and taste, as well as the sequelae of brain fog. With the continuous exploration of biomedical research,We are also increasingly understanding how the new coronavirus affects the nerves of the brainThere will also be breakthroughs in treatment to continue to fight the challenges of the post-epidemic era.
references
1. COVID Live – Coronavirus Statistics – Worldometer
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3. Brain fog: Memory and attention following COVID-19
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7. Parosmia After COVID-19: What to Know
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14. Parosmia: ‘Since I had Covid, food makes me want to vomit’
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16. Cognitive impairment from severe COVID-19 equivalent to 20 years of ageing, study finds
17. Covid-19 smell and taste loss
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19. VCU researchers are developing a device to restore a person’s sense of smell
