How the COVID-19 Virus Impacts the Brain

The world has not been the same since the COVID-19 virus surfaced in 2019. Masks have become the new normal to ensure we all remain safe from the potentially deadly symptoms. The media has made it abundantly clear that the COVID-19 is a dangerous disease impacting the lungs. However, the COVID-19 virus also impacts the brain. Keep reading for the threat COVID-19 poses on the nervous system.

COVID-19 virus impacts the brain
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What is COVID-19?

COVID-19 is a disease belonging to a group of viral illnesses known as Coronavirus. It is also recognized as Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is highly contagious. It spreads primarily through respiratory droplets when an infected person coughs, sneezes, or talks. These droplets can spread up to six feet. Healthy individuals contract the virus by inhaling the particles or touching a service the virus particles is on.

After exposure to the virus, symptoms appear 2 to 14 days later. Symptoms range from mild to life threatening because of severe acute respiratory syndrome. They consist of:

  • Fever or chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Pain or pressure in chest
  • Headache
  • Fatigue
  • Loss of smell or taste
  • Body aches
  • Sore throat
  • Congestion
  • Nausea, vomiting, or diarrhea

COVID-19 Cytokine Storm and Inflammation

The COVID-19 virus causes widespread inflammation. In severe cases that require ICU admissions, the COVID-19 induces what is called a cytokine storm. Cytokines are inflammatory proteins released by immune cells to protect the body against pathogens. The sudden influx of cytokines results in organ damage similar to inflammatory immune conditions such as hemophagocytic lymphohistiocytosis (HLH), which is rarely induced by viral illnesses like the Epstein-Barr virus (EBV). The treatment in viral induced secondary HLH is chemotherapies and immune modulators. Thus, researchers are beginning to test the response to similar treatments due to the poor mortality rate in COVID-19 with a cytokine storm.  

Does the COVID-19 Virus Invade the Brain?

The COVID-19 virus does not directly invade the brain. However, diagnostic imaging shows changes in the brain’s white matter—a large part of the brain that contains millions of nerve fibers which allow the nerves to communicate across the nervous system. In patients who previous suffered from COVID-19, yet are not actively infected with the virus, the white matter becomes necrotic and the cells die off. Experts describe this phenomenon as “diffuse white matter disease.” According to the National Institutes of Health, they are unsure if degradation of white matter stems from a lack of oxygen to the brain or if it is from the inflammatory cytokine storm.

How the COVID-19 Virus Impacts the Brain: Cognition

The “diffuse white matter disease” is related to the long-term cognitive difficulties COVID-19 patients experience. Cognitive skills are the key thinking skills involved in the process of learning, storing information, and complex thinking.

The Cleveland Clinic recently discovered the virus causes inflammation akin to Alzheimer’s dementia with the same elevated markers. Such cognitive impairment Recent studies conclude that up to 65 percent of patients with neurological symptoms present with confusion, and 69 percent with agitation. Cognitive impairment presents with and without visual changes in brain matter.

How the COVID-19 Virus Impacts the Brain: Stroke

Damage to the brain from an interruption or reduction of blood supply is known as a stroke. An ischemic stroke typically occurs when a clog in an artery disrupts blood flow. The symptoms of a stroke come on suddenly. Sudden loss of balance and coordination, slurred speech, facial drooping, one sided weakness, and poor vision. Strokes happen for many reasons, a few being obesity, smoking, high cholesterol, heart arrythmias, diabetes, and now COVID-19.  

Along with full body inflammation, COVID-19 leads to a higher risk of blood clots because the virus produces hypercoagulation of the blood. As the blood clots more easily than normal, these blood clots travel to the heart and brain to cause a stroke.

How the COVID-19 Virus Impacts the Brain: Brain Bleeding

While strokes are common with COVID-19, a subset of patients also have cerebrovascular disease leading to hemorrhaging of the brain. Based on studies conducted by the University of Minnesota, 12 percent of COVID-10 patients with neurological symptoms suffered from a stroke caused directly from an intracranial or cerebral hemorrhage.

The blood vessels in the brain are smaller than normal. With inflammation, they leak blood proteins into the brain tissue. Bleeding in the brain prevents the brain’s nerve cells from communicating functions to the body. The affected portion of the brain impedes those functions because sufficient oxygen is unable to reach the brain.

How the COVID-19 Virus Impacts the Brain: Infection

Whether or not the COVID-19 virus infects the brain is up for debate. However, there is some evidence that viral particles pass the blood-brain barrier in the nervous system. For example, the loss of the sense of smell may indicate that the virus has infiltrated the olfactory bulb. A recent study conducted with animals found virus levels in mice were 1,000 times higher than the levels in other parts of the body. Infection in the brain is dangerous, as it leaves the autonomic nervous system susceptible to malfunctioning, and the autonomic nervous system controls important organ systems (i.e., heart, lungs, etc.).

How the COVID-19 Virus Impacts the Brain: Encephalitis

Encephalitis is inflammation of the brain, which is often due to infection. COVID-19 patients with neurological symptoms like insomnia, headaches, and cognitive impairment frequently exhibit brain swelling indicative of encephalitis on MRI imaging. Like discussed above, when the virus particles enter the blood-brain barrier, macrophages—inflammatory cells—go to the brain. These cells are attempting to attack the virus, but cause greater inflammation instead. The only recourse for COVID-19 related encephalitis is attempt to reduce the inflammation.

How the COVID-19 Virus Impacts the Brain: Nerve Issues and Neuropathy   

Nerve damage and neuropathy is a consequence of COVID-19 that persists long after the virus has left the body. Peripheral nerve injury (PNI) or peripheral neuropathy is damage to the nerves outside of the brain and spinal cord. The symptoms are very painful and impact mobility, as these nerves control the limbs. Patients with COVID-19 have lost function in their hands, shoulder, or feet so profoundly that they require a brace, cane, or wheelchair. At a healthcare facility in Chicago, Illinois, 12 out of 83 COVID-19 patients had lasting nerve injuries. Experts predicted only 10 percent of the patients will make a full recovery, and the recovery that does occur takes up to a year.

How the COVID-19 Virus Impacts the Brain
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How the COVID-19 Virus Impacts the Brain: Delirium  

Delirium can be described a disturbance of mental abilities such as the awareness of one’s environment, confusion, poor memory, difficulty with speech, emotional changes, and abnormal behavior.

There are two types of delirium:

  1. Hyperactive delirium—Patients with hyperactive delirium are restless, aggressive, and suffer from delusions and hallucinations (i.e. seeing or hearing things that do not exist).
  2. Hypoactive delirium—Those with hypoactive delirium are underactive. They have delayed responses, appear drowsy, and communicate little if at all.

Up to 70 percent of critically ill, hospitalized patients with COVID-19 are affected by delirium. A lack of oxygen, an overactive immune system, and the virus attacking the brain are driving factors for delirium.

Becoming delirious is especially prevalent amongst the elderly population. Many physicians assume delirium is worse in old age, but there are younger patients too. Younger COVID-19 patients with delirium are sometimes diagnosed with a mental disorder including depression, anxiety, personality disorders, or schizophrenia. Researchers are still studying whether the mental disorder was previously existing and exacerbated by the COVID-19 virus or if the mental disorders are caused from the virus itself.

How the COVID-19 Virus Impacts the Brain: Low Oxygenation    

With COVID-19 being a respiratory illness low oxygenation, is prevalent complication even in patients who feel asymptomatic. This is called silent hypoxia because shortness of breath does not precede the low blood oxygen levels. Hypoxia is associated with an increased chance of death from the virus. Blood flows through damaged areas of lungs and is unable to retain oxygen. If the patient is experiencing blood clots, these clots can go to the lungs and prevent proper oxygenation. Low blood oxygen levels can be accompanied by increased respiration, which means someone is taking more than 23 breaths per minute.

The Three Stages of COVID-19 Neurological Complications

There is still much to learn about the COVID-19 virus and it’s affect on the nervous system, but scientists have concluded that neurological symptoms are more prevalent than one may think.

Studying COVID-19 patients in China, France, and Germany, Fotuhi and colleagues have proposed a three-stage system to classify neurological complications from the disease:

Stage 1: Nervous system damage consists only of the epithelial cells in the nose and mouth. The symptoms are loss of taste and smell.

Stage 2: Inflammation encompasses the entire body. Systemic inflammation originates in the lungs, but rapidly advances to the body’s organs through the blood vessels. The “cytokine storm” begins, which causes blood clots that leave the body susceptible to small or large strokes.

Stage 3: The cytokine storm continues to wreak havoc as it damages the blood-brain barrier. Inflammatory cells and viral particles infiltrate the brain. Seizures, an altered mental state, coma, or encephalopathy may develop.

References

Chen, L., & Quach, T. (2021). COVID-19 cytokine storm syndrome: a threshold concept. The Lancet Microbe, 2,(2). https://doi.org/10.1016/S2666-5247(20)30223-8

Cleveland Clinic. (2021, June 10). Study identifies how COVID-19 linked to Alzheimer’s disease-like cognitive impairment: Research team used artificial intelligence to uncover association between COVID-19 and brain changes. ScienceDaily. Retrieved June 13, 2021 from www.sciencedaily.com/releases/2021/06/210610162405.htm