Introduction
Encephalopathy is a general term for disorders affecting the brain’s structure and function. If infections are a cause of brain function disruption, it is called infectious encephalopathy. There are 20,000 new cases of infectious encephalopathy reported in the United States each year. A brief review of infectious encephalopathy has been mentioned in the article.
What Is Infectious Encephalopathy?
Infectious encephalopathy refers to the damage and inflammation in the brain induced by infections. The infectious pathogens directly invade the brain tissue or cause an inflammatory response affecting the brain.
What Causes Infectious Encephalopathy?
Viruses and bacteria are the predominant cause of infectious encephalopathy. Infectious encephalopathy is commonly caused by viruses, including those transmitted by mosquitoes and ticks. These agents directly infect the brain. The specific cause could vary depending on immune system status. Rarely, infectious encephalitis is caused by bacteria, fungi, or parasites.
People with underlying medical conditions are more prone to develop this infection. Additionally, individuals with mosquito, tick bites, or weak immune systems are at greater risk for developing the condition.
Some individuals with infectious diseases develop disturbances in brain function, which causes encephalopathy even though the infectious agent does not directly invade the central nervous system. It is known as infectious-disease-associated encephalopathy. Infectious encephalopathy can develop in one area or affect broader regions. Some infectious encephalopathy are found in specific parts of the world.
Viral Causes:
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Herpes Simplex Virus (HSV): HSV type 1 causes cold sores and blisters, and HSV type 2 causes genital herpes and encephalitis. However, infectious encephalitis caused by HSV type 1 is rare and results in significant brain damage and death.
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Herpes Virus: Another herpes virus, like the Epstein-Barr virus, causes infectious mononucleosis, and the varicella-zoster virus causes chickenpox and shingles.
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Enterovirus: Poliovirus and coxsackie virus cause flu-like symptoms with associated eye inflammation and abdominal pain.
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Mosquito-Borne Virus: It causes St Louis, West Nile, La Crosse, and western and eastern equine encephalitis. Symptoms of encephalitis develop within a few days to weeks of exposure.
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Tick-Borne Virus: Ticks carry the Powassan virus, which causes encephalitis. Symptoms develop a week after being infected.
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Rabies Virus: It is transmitted through a bite from an infected animal. Once infected, there is rapid progression to encephalitis.
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Influenza Virus: Severe flu cases can progress into infectious encephalopathy.
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Measles Virus: The virus causes a rare but severe complication known as measles encephalitis.
Bacterial Causes:
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Bacterial Meningitis: Meningitis is brought on by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae, and when it worsens, encephalopathy results.
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Lyme Disease: Bacterium Borrelia burgdorferi is transmitted by ticks and causes Lyme disease. In some, neurological complications like encephalopathy develop.
Fungal and Parasitic Causes:
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Fungal infections like cryptococcal meningitis cause encephalopathy.
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Toxoplasma gondii or Trypanosoma brucei can cause encephalopathy sometimes.
Systemic Infections: Rarely, infections in other body parts spread to the brain, causing secondary encephalopathy.
Immune Responses: The body’s immune response to infections sometimes induces inflammation and damages the brain, causing encephalopathy.
What Is the Pathophysiology for Developing Infectious Encephalopathy?
Different infectious agents have unique pathophysiologies. Some viruses have a preference towards specific cell types within the brain, while bacteria produce toxins that damage the neuronal tissue.
Some infectious microorganisms enter the central nervous system through direct infection or along the nerve pathway. The blood-brain barrier helps protect the brain from infection, but there is a risk for some microorganisms to breach the barrier. The immune system identifies the presence of infection in the central nervous system and initiates an immune response. It activates the immune cells like microglia, which release inflammatory mediators. Inflammatory mediators are responsible for causing inflammation in the brain tissue. When the inflammatory response becomes uncontrollable, it causes damage to the brain tissue. Chemokines, cytokines, and inflammatory cells have an active role in inducing tissue damage.
The immune response and inflammation also contribute to neuronal dysfunction and damage. Immune cells, oxidative stress, and disruption of neuronal function cause neuronal damage. Additionally, infectious encephalopathy disrupts neurotransmission, resulting in symptoms of seizures, altered consciousness, and cognitive impairment.
Immune response and inflammation cause fluid accumulation in brain tissue, leading to intracranial pressure. Elevated pressure within the skull further exacerbates neurological symptoms and complications.
Some infectious microorganisms affect blood vessels within the brain and cause vascular changes. The development of vasculitis, thrombosis, and hemorrhage further contributes to tissue damage and neuronal dysfunction.
What Are the Symptoms of Infectious Encephalitis?
Symptoms depend on the infectious organism causing the infection. Commonly developing symptoms are seizures, problems with movement, altered mental status, vision, balance, thinking, mood, or behavioral changes. Some symptoms persist for the long term, even if the condition has been adequately treated. Some individuals rarely develop brain infections as a response to the original infection. Severe cases of infectious encephalitis lead to coma and death.
How Is Infectious Encephalitis Diagnosed?
Doctors will perform physical exams to look for brain damage or signs of skin rash. Blood and spinal fluid tests help identify causative organisms of the infection and the body’s response to treatment. CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) scans help detect affected brain parts. An Electroencephalogram (EEG) is done to determine the risk of seizure.
How Is Infectious Encephalitis Treated?
Early recognition and treatment are vital for managing infectious encephalopathy. Antibacterial and antivirals are the most prescribed medications. Medications help eliminate infections and are used for overcoming associated problems like fatigue, memory disruption, and depression. To enable recovery, the patients require a multidisciplinary approach, which includes physical, occupational, and speech therapy. During rehabilitation, the patient may need assistance from physical or assistive devices for some activities.
Infectious encephalopathy has long-term implications for the patient's health. Therefore, families must help such patients by assisting. Children affected by this condition require assistance and changes at home and school. Working adults who develop infectious encephalopathy require changes at work.
Preventive measures such as vaccines against specific bacteria and viruses can reduce the risk of developing infectious encephalitis. Additionally, follow suitable hygiene measures, avoid contact with infectious surfaces, and take precautions in endemic areas of infection.
Conclusion
Infectious encephalopathy is a brain tissue inflammation caused by an infectious agent. Several microorganisms, such as viruses, bacteria, fungi, or parasites, cause infectious encephalopathy. Infection with viral agents is more common. Treatment depends on the infectious cause of the disease.
