CORONAVIRUUS
AND
THE NERVOUS SYSTEM
By
Søren Nielsen
2021
What is SARS-CoV-2 and COVID-19?
Coronaviruses are common causes of usually mild to moderate upper respiratory tract illnesses like the common cold, with symptoms that may include runny nose, fever, sore throat, cough, or a general feeling of being ill.
However, a new coronavirus called Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) emerged and spread to cause the COVID-19 pandemic.
COVID-19, which means Coronavirus disease 2019, is an infectious disease that can affect people of all ages in many ways.
It is most dangerous when the virus spreads from the upper respiratory tract into the lungs to cause viral pneumonia and lung damage leading to Acute Respiratory Distress Syndrome (ARDS).
When severe, this impairs the body’s ability to maintain critical levels of oxygen in the blood stream—which can cause multiple body systems to fail and can be fatal.
What do we know about the effects of SARS-CoV-2 and COVID-19 on the nervous system?
Much of the research to date has focused on the acute infection and saving lives.
These strategies have included preventing infection with vaccines, treating COVID-19 symptoms with medicines or antibodies, and reducing complications in infected individuals.
Research shows the many neurological symptoms of COVID-19 are likely a result of the body’s widespread immune response to infection rather than the virus directly infecting the brain or nervous system.
In some people, the SARS-CoV-2 infection causes an overreactive response of the immune system which can also damage body systems.
Changes in the immune system have been seen in studies of the cerebrospinal fluid, which bathes the brain, in people who have been infected by SARS-CoV-2.
This includes the presence of antibodies—proteins made by the immune system to fight the virus—that may also react with the nervous system.
Although still under intense investigation, there is no evidence of widespread viral infection in the brain.
Scientists are still learning how the virus affects the brain and other organs in the long-term.
Research is just beginning to focus on the role of autoimmune reactions and other changes that cause the set of symptoms that some people experience after their initial recovery.
It is unknown if injury to the nervous system or other body organs cause lingering effects that will resolve over time, or whether COVID-19 infection sets up a more persistent or even chronic disorder.
What are the immediate (acute) effects of SARS-CoV-2 and COVID-19 on the brain?
Most people infected with SARS-CoV-2 virus will have no or mild to moderate symptoms associated with the brain or nervous system.
However, most hospitalized patients do have symptoms related to the brain or nervous system, most commonly including muscle aches, headaches, dizziness, and altered taste and smell.
Some people with COVID-19 either initially have, or develop in the hospital, a dramatic state of confusion called delirium.
Although rare, COVID-19 can cause seizures or major strokes.
Muscular weakness, nerve injury, and pain syndromes are common in people who require intensive care during infections.
There are also very rare reports of conditions that develop after SARS-CoV-2 infection, as they sometimes do with other types of infections.
These disorders of inflammation in the nervous system include Guillain-Barré syndrome (which affects nerves), transverse myelitis (which affects the spinal cord), and acute necrotizing leukoencephalopathy (which affects the brain).
Bleeding in the brain, weakened blood vessels, and blood clots in acute infection.
The SARS-CoV-2 virus attaches to a specific molecule (called a receptor) on the surface of cells in the body.
This molecule is concentrated in the lung cells but is also present on certain cells that line blood vessels in the body.
The infection causes some arteries and veins – including those in the brain – to become thin, weaken, and leak.
Breaks in small blood vessels have caused bleeding in the brain (so-called microbleeds) in some people with COVID-19 infection.
Studies in people who have died due to COVID-19 infection show leaky blood vessels in different areas of the brain that allow water and a host of other molecules as well as blood cells that are normally excluded from the brain to move from the blood stream into the brain.
This leak, as well as the resulting inflammation around blood vessels, can cause multiple small areas of damage.
COVID-19 also causes blood cells to clump and form clots in arteries and veins throughout the body.
These blockages reduce or block the flow of blood, oxygen, and nutrients that cells need to function and can lead to a stroke or heart attack.
A stroke is a sudden interruption of continuous blood flow to the brain.
A stroke occurs either when a blood vessel in the brain becomes blocked or narrowed or when a blood vessel bursts and spills blood into the brain.
Strokes can damage brain cells and cause permanent disability.
The blood clots and vascular (relating to the veins, capillaries, and arteries in the body) damage from COVID-19 can cause strokes even in young healthy adults who do not have the common risk factors for stroke.
COVID-19 can cause blood clots in other parts of the body, too.
A blood clot in or near the heart can cause a heart attack.
A heart attack or Inflammation in the heart, called myocarditis, can cause heart failure, and reduce the flow of blood to other parts of the body.
A blood clot in the lungs can impair breathing and cause pain.
Blood clots also can damage the kidneys and other organs.
Low levels of oxygen in the body (called hypoxia) can permanently damage the brain and other vital organs in the body.
Some hospitalized individuals require artificial ventilation on respirators.
To avoid chest movements that oppose use of the ventilator it may be necessary to temporarily "paralyze" the patient and use anesthetic drugs to put the individual to sleep.
Some individuals with severe hypoxia require artificial means of bringing oxygen into their blood stream, a technique called extra corporeal membrane oxygenation (ECMO).
Hypoxia combined with these intensive care unit measure generally cause cognitive disorders that show slow recovery.
Diagnostic imaging of some people who have had COVID-19 show changes in the brain’s white matter that contains the long nerve fibers, or "wires," over which information flows from one brain region to another.
These changes may be due to a lack of oxygen in the brain, the inflammatory immune system response to the virus, injury to blood vessels, or leaky blood vessels.
This "diffuse white matter disease" might contribute to cognitive difficulties in people with COVID-19.
Diffuse white matter disease is not uncommon in individuals requiring intensive hospital care but it not clear if it also occurs in those with mild to moderate severity of COVID-19 illness.
What is the typical recovery from COVID-19?
Fortunately, people who have mild to moderate symptoms typically recover in a few days or weeks.
However, some people who have had only mild or moderate symptoms of COVID-19 continue to experience dysfunction of body systems—particularly in the lungs but also possibly affecting the liver, kidneys, heart, skin, and brain and nervous system—months after their infection.
In rare cases, some individuals may develop new symptoms (called sequelae) that stem from but were not present at the time of initial infection.
People who require intensive care for Acute Respiratory Distress Syndrome, regardless of the cause, usually have a long period of recovery.
Individuals with long-term effects, whether following mild or more severe COVID-19, have in some cases self-identified as having "long COVID" or "long haul COVID".
These long-term symptoms are included in the scientific term, Post Acute Sequelae of SARS-CoV-2 Infection (PASC).
What are possible long-term neurological complications of COVID-19?
Researchers are following some known acute effects of the virus to determine their relationship to the post-acute complications of COVID-19 infection.
These post-acute effects usually include fatigue in combination with a series of other symptoms.
These may include trouble with concentration and memory, sleep disorders, fluctuating heart rate and alternating sense of feeling hot or cold, cough, shortness of breath, problems with sleep, inability to exercise to previous normal levels, feeling sick for a day or two after exercising (post-exertional malaise), and pain in muscle, joints, and chest.
It is not yet known how the infection leads to these persistent symptoms and why in some individuals and not others.
How do the long-term effects of SARS-CoV-2 infection/COVID-19 relate to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)?
Some of the symptom clusters reported by people still suffering months after their COVID-19 infection overlap with symptoms described by individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
People with a diagnosis of ME/CFS have wide-ranging and debilitating effects including fatigue, PEM, unrefreshing sleep, cognitive difficulties, postural orthostatic tachycardia, and joint and muscle pain.
Unfortunately, many people with ME/CFS do not return to pre-disease levels of activity.
The cause of ME/CFS is unknown but many people report its onset after an infectious-like illness.
Rest, conserving energy, and pacing activities are important to feeling better but don’t cure the disease.
Although the long-term symptoms of COVID-19 may share features with it, ME/CFS is defined by symptom-based criteria and there are no tests that confirm an ME/CFS diagnosis.
ME/CFS is not diagnosed until the key features, especially severe fatigue, post-exertional malaise, and unrefreshing sleep, are present for greater than six months.
It is now becoming more apparent that following infection with SARS-CoV-2/COVID-19, some individuals may continue to exhibit these symptoms beyond six months and qualify for an ME/CFS diagnosis.
It is unknown how many people will develop ME/CFS after SARS-CoV-2 infection.
It is possible that many individuals with ME/CFS, and other disorders impacting the nervous system, may benefit greatly if research on the long-term effects of COVID-19 uncovers the cause of debilitating symptoms including intense fatigue, problems with memory and concentration, and pain.
Am I at a higher risk if I currently have a neurological disorder?
Much is still unknown about the coronavirus but people having one of several underlying medical conditions may have an increased risk of illness.
However, not everyone with an underlying condition will be at risk of developing severe illness.
People who have a neurological disorder may want to discuss their concerns with their doctors.
Because COVID-19 is a new virus, there is little information on the risk of getting the infection in people who have a neurological disorder.
People with any of these conditions might be at increased risk of severe illness from COVID-19:
1 : Cerebrovascular disease.
2 : Stroke.
3 : Obesity.
4 : Dementia.
5 : Diabetes.
6 : High blood pressure.
There is evidence that COVID-19 seems to disproportionately affect some racial and ethnic populations, perhaps because of higher rates of pre-existing conditions such as heart disease, diabetes, and lung disease.
Social determinants of health (such as access to health care, poverty, education, ability to remain socially distant, and where people live and work) also contribute to increased health risk and outcomes.
Does the COVID-19 vaccine cause neurological problems?
Almost everyone should get the COVID-19 vaccination.
It will help protect you from getting COVID-19.
The vaccines are safe and effective and cannot give you the disease.
Most side effects of the vaccine may feel like flu and are temporary and go away within a day or two.
In early vaccine development, there were extremely rare reports of unexplained neurological illness following COVID-19 vaccination, but regulators found no evidence the vaccines caused the illness.
The U.S. Food and Drug Administration (FDA) continues to investigate any report of adverse consequences of the vaccine and none have appeared as of yet.
Consult your primary care doctor or specialist if you have concerns regarding any pre-existing known allergic or other severe reactions and vaccine safety.
Scientists are studying the risk to benefit ratio of the vaccine in someone who previously developed Guillain Barré syndrome after a vaccination.
The general sense is the COVID-19 vaccine is safe in individuals whose Guillain-Barré syndrome was not associated with a previous vaccination.
