The current COVID-19 pandemic has everyone on the edge of their seat with new information about the virus coming constantly. Initially, COVID-19 was presented by health authorities as a severe respiratory infection of viral origin caused by a SARS-like Coronavirus dubbed SARS-CoV-2. Typical of respiratory infections, it produced symptoms such as a sore throat, coughing, fever, chills and shaking and nasal congestion. Severe forms of the disease caused pneumonia with shortness of breath, low oxygenation and respiratory failure and COVID-19-related lung function impairment with long-term damage.
Soon into the pandemic it was revealed that a growing number of people infected with the novel Coronavirus do not even exhibit symptoms or are sub-clinically symptomatic which means they symptoms are so mild they go under the radar and evade diagnosis, but can infect others nonetheless. Then we were informed about more atypical symptoms such as the loss of smell and taste which occur in the early stages of a Coronavirus infection. There is also a rash with the novel Coronavirus infection which is one of the more unusual COVID-19 symptoms since respiratory tract infections are not normally associated with skin symptoms.
In addition to blood clotting issues that predisposed to cardiovascular events such as strokes and complications such as kidney damage and liver damage, the already broad symptomatology of COVID-19 was only recently announced to further include neurological symptoms. The recent discovery shines a new light on symptoms such as headaches or migraines and dizziness reported by COVID-19 sufferers and helps paint a clearer image of what is the novel Coronavirus infection. From under the radar symptoms such as headaches and dizziness to more severe complications, read on to find out what are these common neurological symptoms of COVID-19 and how they come to be.
(1) Headaches and migraines
At this point in the COVID-19 pandemic it is a well-known fact that the novel Coronavirus SARS-CoV-2 infiltrates cells via ACE2, or the angiotensin-converting enzyme 2. This enzyme is present on the surface of many cells in the human body including some lung cells (lung type 2 cells), some intestinal cells (intestinal absorptive cells), skeletal muscle cells, endothelial cells lining the interior of blood vessels and also nervous system cells such as cells in the cerebral cortex, corpus striatum, hypothalamus and brainstem, according to an article in Molecular Pharmacology. Animal studies have also shown that SARS-CoV-1, the Coronavirus causing the 2002-2004 SARS epidemic, and close relative of the novel Coronavirus SARS-CoV-2, also targets the central nervous system (see PDF source) via the ACE2 expressed on the surface of nerve cells.
Given our current knowledge of the novel Coronavirus and other human Coronaviruses’ ability to infect the nervous system and factual data on the functions of various central nervous system components (e.g. the brainstem and pain sensitivity control), it stands to reason the infiltration of the novel Coronavirus SARS-CoV-2 in nerve cells can potentially cause neurological symptoms such as headaches and migraines. Indeed there are reports all over social media of strange or unusual symptoms associated with COVID-19, including headaches and migraines ranging in intensity from mild to severe. Headaches are currently reported as one of the early, if not earliest signs and symptoms of a Coronavirus infection.
In an April 10, 2o20 study of 214 COVID-19 patients from the Union Hospital of Huazhong University of Science and Technology in Wuhan, China, the most common symptom reported was dizziness, present in 36 patients (or 16.8%). It was closely followed by headaches and loss of taste and smell, among other neurological symptoms (see study). The neurotropic effects of the novel Coronavirus SARS-CoV-2 are the source of neurological symptoms such as dizziness. Such symptoms were reported both in the early stages of the novel Coronavirus infection and in late phases of the disease, both mild and severe forms.
As it infects nerve cells because of their ACE2 receptors, the novel Coronavirus affects parts of the nervous system responsible for maintaining consciousness, but also brain centers for balance, hence the dizziness and even vertigo symptoms. Depending on the parts of the nervous system affected by the virus, centers for respiratory control and cardiovascular system control may also be affected, potentially resulting in drops in blood pressure or changes in heart rhythm that could further lead to dizziness and also alterations of consciousness.
(3) Loss of smell and taste
Loss of taste and smell are 2 of the most unusual symptoms of COVID-19. They are unusual in the sense that they wouldn’t normally be associated with a respiratory infection, which COVID-19 is, but rather with other conditions such as seasonal allergies, which the current pandemic happens to overlap. But there is a pretty good explanation as to how COVID-19 can cause changes in smell and taste perception.
The novel Coronavirus causing the current COVID-19 pandemic, dubbed SARS-CoV-2, infects cells that have the ACE2 receptor on their surface. Cells with this receptor are found throughout the nervous system, in the brainstem, cerebral cortex, corpus striatum, hypothalamus and other regions. In some of these regions there are centers for sensory perception that process data sent to the brain by our senses. For example, the cerebral cortex, which also happens to be a point of infection by the novel Coronavirus, is responsible, among other things, for perception (taste, smell, sight, sound, touch etc.).
Since infected cells are taken over by the virus which uses them as its own replication machine, they no longer respond to stimuli correctly and the olfactive and gustatory perception is impacted. This results in lowered ability to smell and taste, distortions of the two senses (e.g. metallic taste in the mouth) and even complete loss of smell and taste. Approximately 2 out of 3 or 30% of confirmed Coronavirus cases experienced some degree of loss of smell, based on data from South Korea, China, Germany and Italy. See source. Fortunately, the symptoms are reversible, although it may take anywhere from a few days to 3 weeks or more for smell and taste perception to be recovered. Loss of smell and taste and altered olfactive and gustatory perception represent two of the earliest signs of a Coronavirus infection.
(4) Myalgia, or muscle pain
Myalgia is the fancy word for muscle pain. It includes manifestations such as tenderness, soreness and pain in muscles. Myalgia is a well-documented symptom of respiratory infections such as influenza or the flu. And now it’s known to also occur with COVID-19 along with other types of body aches and pain. Muscles in general are controlled by the nervous system – there is actually a finely-tuned play between stimuli from the environment and nervous system activity that results in our high-functioning motor skills.
The novel Coronavirus SARS-CoV-2 has been proven to infect both nerve cells and muscle cells. Infection of cells with a pathogenic agent incurs immune system involvement which implies an initial inflammatory phase. If the immune system response is strong, there is a proportional inflammatory response which leads to abnormalities in muscle function such as tenderness and pain. In the same study cited above it was revealed that skeletal muscle injury occurred in 23 of 214 COVID-19 patients, which amounted to 10.7% of cases. Limb twitching, muscle contractions and other muscular manifestations are also possible.
(5) Muscle weakness, ataxia
Muscle pain with COVID-19 is theorized to be caused primarily by immune system involvement and worsened to the point of injury by a phenomenon known as a cytokine storm (find out more about what COVID-19 does to the body). But in the case of muscle weakness and ataxia (lack of muscle coordination), it is theorized that nervous system abnormalities due nerve cell damage as a result of infection with the novel Coronavirus SARS-CoV-2 are the most likely cause.
In simple terms, the novel Coronavirus binds to nerve cells via a receptor enzyme known as ACE2 (angiotensin-converting enzyme 2) present on the surface of nerve cells throughout the nervous system, and other types of cells in the body. Infected cells are taken control over by the virus for viral replication and are longer able to perform their usual functions, resulting in abnormalities in the functioning of the nervous system. And since the nervous system coordinates muscle activity, weakness and loss of the ability to coordinate muscle movement (ataxia) may occur as a result. However, a too strong immune system response causing extensive inflammation and subsequent nervous system abnormalities cannot be ruled out as a cause either.
(6) Lethargy and confusion
Infection with the novel Coronavirus produces neurological symptoms such as an altered state of consciousness which may include sleepiness, lethargy, confusion and up to loss of consciousness. All symptoms of the kind have been reported in more advanced phases of the disease and are believed to be caused directly by the virus action on the nervous system (i.e. infection of nerve cells and subsequent damage). For example, SARS-CoV-2 can affect the centers of the brain responsible for alertness, awareness, consciousness, hence symptoms such as lethargy and confusion.
(7) Hallucinations and delirium
In more severe forms of COVID-19, symptoms such as delirium may occur. Due to fluctuating consciousness (falling in and out of consciousness), confusion, disorientation, incoherent speech and even hallucinations may occur. Delirium is accompanied by anxiety and emotional distress. It is not clear yet if such severe symptoms are a direct result of the effects of the novel Coronavirus on the nervous system, or side effects of a systemic infection.
From data collected up to this point, it has been suggested that Coronavirus infections that present with more severe neurological symptoms such as lethargy and confusion have a higher chance of progressing to seizures and even coma. Such symptoms strongly indicate extensive neurological involvement.
(9) Brain inflammation (encephalitis)
Whether a direct result of SARS-CoV-2 infection of the brain or immune system involvement, COVID-19 can cause, in severe forms, brain inflammation. Medical literature documents encephalitis as a common complication of viral infections. Symptoms such as poor muscle coordination (ataxia), incoherent speech, falling in and out of consciousness are predictive. Seizures are a telling sign of encephalitis and immediate measures must be taken to prevent more dire outcomes. Even after recovery there is a chance of long-term sequelae brought on by neuronal death.
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