Table of Contents
Introduction
The coronavirus disease 2019 (COVID-19) epidemic first surfaced in Wuhan, China, in December 2019, drawing attention worldwide. Acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is particularly severe. According to a recent study, 36.4 percent of COVID-19 patients also experience neurological symptoms, such as headache, altered consciousness, paresthesia (prickling sensation in different parts of the body), and systemic and respiratory symptoms. Those with severe disease are more likely to experience neurological symptoms than those with mild or moderate illnesses.
Edema in the brain tissue of deceased patients has been documented in postmortem reports. Additionally, some hospitals announced a case of viral encephalitis (inflammation of the brain) on March 4, 2020, which was brought on by a brand-new coronavirus (CoV) that was attacking the central nervous system (CNS) for the first time. By genome sequencing, the researchers verified the presence of SARS-CoV-2 in the cerebral fluid. Furthermore, it demonstrated the potential for COVID-19 to harm the neurological system. Therefore, it is crucial to educate practitioners about the effects different CoV infections have on the CNS in light of the current COVID-19 pandemic.
How Do COVID-19 Infections Affect the Central Nervous System?
Numerous viral infections, including those that affect the central nervous system (CNS) and can result in severe encephalitis, toxic encephalopathy (a condition in which toxins hamper the function of the brain), and painful acute demyelinating lesions (a condition that causes damage to the protective covering surrounding the nerve fibers in the brain), can seriously harm the structure and function of the nervous system. Some viruses can enter neural tissues and infect immune-active macrophages (a large cell at the site of the infection), microglia (cells that function as scavengers in the CNS), or astrocytes (cells) in the central nervous system (CNS).
CoV is spherical or oval and has an average diameter of 100 nm. These negatively stained virus particles include huge spikes of viral membrane glycoproteins on the surface and have the typical crown-like structure when viewed under an electron microscope. CoV is a positive-sense single-stranded RNA (ribonucleic acid) virus with a genomic length of around 26 to 32 kb. It is the largest known RNA virus.The novel CoV 2019 (SARS-CoV-2), the seventh known CoV that can infect humans, is the current novel pneumonia outbreak's pathogen. The other six CoVs are HCoV-229E, HCoV-OC43, HCoV-NL63, HCoV-HKU1, SARS-CoV, and MERS-CoV.
Which Are the Important Types of Coronavirus (CoV) Infections With Potential Nervous System Damage?
The most common and important types of CoV are:
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SARS-CoV: SARS-CoV is a zoonotic respiratory disease that originated in Asia and has now spread worldwide. It concerns human health because of its acute onset and potent infectiousness. The primary clinical signs of SARS include fever, chills, a dry cough, and breathing problems. Respiratory failure and death could happen in severe circumstances. SARS-CoV can also cause neurological conditions such as encephalitis and aortic ischemic stroke (a clot blocks the blood supply to brain parts). Studies on autopsies showed that most SARS cases exhibit indications of cerebral edema (swelling of the brain). Additionally, SARS-CoV virus particles and genome sequences, monocyte and lymphocyte infiltration in the artery wall, ischemia changes of neurons, demyelination of nerve fibers, and ischemic alterations of neurons could all be found in the brain.
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MERS-CoV: The camel is the intermediate host for the MERS-CoV virus, which causes middle east respiratory syndrome (MERS). Patients with MERS-CoV infection frequently exhibit signs of pneumonia, including fever, myalgia (pain in muscle), coughing, and dyspnea. Acute respiratory distress syndrome (ARDS), septic shock, multiple organ failure, and death can result from severe cases. A retrospective investigation indicated that 25.7 percent of MERS patients could become insane, and 8.6 percent had convulsions. MERS-CoV is known to be potentially brain invasive. Additionally, during the illness, nearly a fifth of MERS-CoV patients experience neurological symptoms, such as paralysis, ischemic stroke, other forms of poisoning, or infectious neuropathy, among others. It is interesting to note that their neurological issues arrive two to three weeks later without respiratory symptoms.
- SARS-CoV-2: SARS-CoV-2 and SARS-CoV share 79.5 perecnt of their genetic makeup, whereas SARS-CoV and bat coronavirus share 96 percent. With a mortality rate of two to four percent, patients infected with SARS-CoV-2 exhibit a range of symptoms, from fever or a moderate cough to pneumonia and significant involvement of several organ functions. According to current clinical evidence, some COVID-19 patients experience symptoms like headache, epilepsy, and altered consciousness comparable to those of intracranial infections (caused by bacteria or viruses, which are life-threatening). Additionally, many COVID-19 patients mention a sudden loss of taste or smell. Therefore, it is conceivable that COVID-19 patients may experience anosmia (loss of smell). In some cases, neurologic symptoms come on first before COVID-19-related symptoms.
What Are the Nervous System Diseases Related to CoV Infections?
Some of the diseases are mentioned below:
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Viral Encephalitis: Encephalitis is the term used to describe inflammatory lesions in the brain parenchyma (functional tissue of the brain making up two cells of the brain) brought on by infections, including lesions to the nerve tissue and damage to neurons. It has an abrupt onset, and typical symptoms include headache, fever (often a high fever), vomiting, convulsions, and problems with consciousness. It is crucial to identify viral encephalitis early. The treatment staff at some hospitals identified SARS-CoV-2 through genome sequencing in the cerebrospinal fluid of COVID-19 patients, proving clinically that viral encephalitis was present in the continuing pneumonia pandemic. This gave strong support to the idea that CoV can cause encephalitis.
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Infectious Toxic Encephalopathy: Acute toxic encephalitis, often called contagious, poisonous encephalopathy, is a form of reversible brain dysfunction condition brought on by systemic toxicity, metabolic abnormalities, and hypoxia throughout acute infection. Cerebral edema is one of the primary clinical alterations in this illness, and an examination of the cerebrospinal fluid (CSF) revealed no signs of inflammation. Clinical signs of it are numerous and complex. Patients with the condition in a milder stage may experience headaches, mental illness, and delirium (disturbed state of mind). Severely afflicted patients may experience confusion, unconsciousness, coma, and paralysis. A respiratory infection brought on by CoV is an example of how acute viral infection is also a significant contributor to this illness. The extreme hypoxia (deficiency of oxygen in tissues) and viremia (presence of viruses in the blood) that COVID-19 patients frequently experience have the potential to result in toxic encephalopathy. In addition, over 40 percent of COVID-19 patients have headaches, altered awareness, and other indications of brain dysfunction, and autopsy research revealed that edema had been found in the brain tissue of COVID-19 patients. The results show that COVID-19 may induce infectious, toxic encephalopathy, while further research is urgently needed.
Conclusion
The nervous system can be affected by CoV infections, and it is currently thought that CoV, along with host immune systems, may cause these infections to become persistent infections that may result in neurological disorders. Therefore, neurological symptoms like headache, consciousness problems, paresthesia, and other pathological indications should be assessed in patients with CoV infections as soon as possible. In addition, the prognosis of critically ill patients can be improved by timely cerebrospinal fluid investigation.
