Dr. Sandra El Hajj - MSc, N-MD, DHSc
All over the world, one virus is occupying the minds of populations and doctors: A new type ofzoonotic disease that found its way to infect human beings. COVID-19 began its spread a few months ago leading to global distress everywhere and at many levels. Morbidity and mortality rates were through the roof. We are talking about a viral infection that is capable of causing distress on your brain.
The brain is an organ made up of a large mass of nerve tissue that’s protected within the skull. It plays a role in just about every major body system. Some of its main functions include the processing of sensory information, regulation of blood pressure and breathing, as well as the regulation of hormonal release. The functions of the brain are highly dependent on its physiological parts, such as the cerebrum, cerebellum, diencephalon and brain stems.
The cerebrum is the largest part of the brain(1). It’s divided into two halves, called hemispheres. Each hemisphere of the cerebrum is divided into broad regions called lobes. Each lobe is associated with different functions. The frontal lobes coordinate high-level behaviors, such as motor skills, problem-solving, judgment, planning and attention. The frontal lobes also manage emotions and impulse control. The parietal lobes are involved in organizing and interpreting sensory information from other parts of the brain. The temporal lobes coordinate specific functions, including visual memory, verbal memory, and interpreting the emotions and reactions of others. The occipital lobes control the ability to read and recognize printed words, along with other aspects of vision.
The cerebellum is located in the back of the brain, just below the occipital lobes. It’s involved with fine motor skills, which refer to the coordination of smaller, or finer, movements, especially those involving hands and feet. It also helps the body maintain its posture, equilibrium, and balance.
The diencephalon (also known as the interbrain) is located at the base of the brain where the thalamus, epithalamus and hypothalamus are found. The thalamus is involved in consciousness, sleep and memory. The epithalamus is involved with emotion, long-term memory and behavior. The hypothalamus helps maintain homeostasis (i.e. stability/consistency).
The brain stem is located in front of the cerebellum and connects to the spinal cord. It consists of three major parts namely midbrain, pons and medulla oblongata.
Aside from causing respiratory damage, COVID-19 can also affect brain functions(2). Neurologic symptoms such as dizziness, headaches, weakness and fatigue, muscle pain, loss of taste and smell, and impaired thinking were reported by at least one-third of infected individuals.
In addition, there are psychiatric symptoms that are not directly related to the virus, but to the consequences of the pandemic itself such as post-traumatic stress disorder (mainly among frontline healthcare professionals), anxiety disorders and depression. Other effects include substance use disorders as a consequence of psychosocial stress, ongoing fear, social isolation, bereavement, job loss, financial insecurity and loss of purpose.
Some psychiatric drugs are being studied for their potential to diminish some of the acute harm caused by the virus (3). For example, the antidepressant fluvoxamine has anti-inflammatory properties which might help prevent some COVID-19 complications from a surge in inflammatory chemicals.
Disruption of brain functions may lead to the development of strokes, seizures and slower cognitive functions affecting perception, memory, learning ability, attention, decision making and language abilities. A study in JAMA Neurology(3) found that more than 36 percent of 214 patients in Wuhan, China, experienced neurologic symptoms during the course of their COVID-19 illness. The associated symptoms were dizziness, headache, stroke and loss of taste and smell.
Unfortunately, there is a lack of data pointing to how the virus specifically affects the brain. One theory circulating in the scientific and medical communities is that the virus may enter the nervous system through theolfactory bulb. This will help it gain access to the brain through the nasal cavity allowing it to transmit information from the nose to the brain.
Such a theory can explain why many people with COVID-19 report a loss of smell or taste as part of the list of symptoms. Another theory is that the body's reaction to the infection is what causes some sort of nervous system damage in some people with COVID-19. When the body fights the virus, an immune response can trigger dizziness and headaches. Also, because difficulty breathing is common among people with moderate to severe cases of COVID-19, there is a possibility that a primary infection could take place in the brain stem primarily.
This can affect the respiratory centers that are in control of breathing. An infection in this part of the brain could worsen the respiratory failure of the patient. Currently, there is no clear data that proves whether we are dealing with a direct brain infection by the virus, or if it's secondary to the systemic inflammation causing a disturbance in brain functions.
Experts say that injury to the brain and nervous system could also be due to a loss of oxygen from damaged lungs that may lead to multisystem organ failure. Another complication is when a patient develops a stroke caused by the formation of blood clots. These are likely triggered by COVID-19's effects on the body's clotting system or may be the result of a severe illness. The blood clots formed can lead to life-threatening conditions in people with COVID-19, including stroke.
It's unclear whether COVID-19's impact on the nervous system has any long-term effects on the brain’s health, but it's something researchers hope to better understand. What the body of research has revealed so far is that some complications seem to be “more transient” than others, such as loss of smell(4). Other neurological events, including stroke, can leave more permanent damage.
Acute necrotizing encephalopathy (ANE) is a rare disease characterized by respiratory or intestinal infection as a complication of influenza and other viral infections, particularly affecting adults. It is often fatal. Recently, a patient who tested positive for COVID-19 presented with a three-day history of cough, fever and altered mental status was suspected to have developed ANE as a result of the infection. An MRI scan revealed that the patient had lesions in the brain with internal hemorrhages affecting consciousness, sensation and memory functions. Doctors must be careful to detect symptoms of ANE among patients positive for COVID-19 since it can cause serious complications.
COVID-19 is a new virus that yet needs to be fully understood. Such enlightenment will be brought by the manifestations happening in patients, all over the world. Still taking its course, more connections will be made clearer. Every day is bringing new findings to the etiology of the virus, its imparted damages on the human body and the many possible beneficial treatments. Studies are still ongoing and no clear statement is being adopted as far the progress of the disease in our organs.