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Mysterious Cause of Encephalitis: Why Do These Viruses Trigger Deadly Brain Inflammation?
Encephalitis is an inflammation of the brain. There are various factors that affect the cause and course of the disease, and it can strongly affect the patient's consciousness and behavior. Generally speaking, encephalitis can be mild or severe, with symptoms including reduced or altered consciousness, aphasia, headache, high fever, confusion, stiff neck, and vomiting. Some complications can cause seizures, hallucinations, speech problems, memory impairment, hearing problems, and more. Causes of encephalitis include viruses, such as herpes simplex virus and rabies virus, as well as bacteria, fungi, or parasites. Additionally, autoimmune diseases and certain medications may be the cause, and in many cases, the cause remains unknown.
In 2015, encephalitis affected an estimated 4.3 million people worldwide, resulting in 150,000 deaths.
Signs and symptoms of encephalitis
When encephalitis occurs in adults, it is usually an acute onset of high fever, headache, confusion, and sometimes seizures. Young children or infants may show irritability, loss of appetite, and high fever. Neurological examination usually reveals a lethargic or confused condition, and a stiff neck due to meningeal irritation suggests the possibility of meningitis or meningoencephalitis.
Limbic encephalitis
Limbic encephalitis refers to an inflammatory disease limited to the limbic system of the brain. Clinical manifestations often include disorientation, loss of inhibition, memory loss, seizures, and behavioral abnormalities. MRI imaging shows T2 high signal intensity in medial temporal lobe structures, and sometimes other limbic structures are also affected.
Encephalitis lethargy
Identifying features of encephalitis lethargica include high fever, headache, delayed body reactions, and drowsiness. Individuals may experience upper body weakness, muscle pain, and tremors, although the specific cause of encephalitis lethargica is currently unknown. Between 1917 and 1928, a global epidemic of encephalitis lethargica occurred.
Causes of encephalitis
The cause of approximately 30% to 40% of encephalitis cases is unknown. Viral infection is the most common cause of infectious encephalitis, which may be a direct consequence of acute infection or a sequelae of latent infection. The cause of most viral encephalitis is unknown, but an identifiable cause is usually an infection from the herpes simplex virus. Other causes of acute viral encephalitis include rabies virus, poliovirus, and measles virus.
Various possible viral causes include West Nile virus, La Crosse virus, lymphocytic chorioencephalitis virus, and others.
Bacterial encephalitis
Bacterial encephalitis may be caused by a bacterial infection, such as bacterial meningitis, or may be a complication of another infectious disease, such as syphilis. Other pathogens, such as mycoplasma and the bacteria that cause rickettsial disease, can also cause meningitis and, subsequently, encephalitis.
Other infectious causes
Certain parasitic or protozoan infections, such as Toxoplasma gondii and malaria, may also cause encephalitis in people with weakened immune systems. Some rare but often fatal forms of encephalitis, such as primary amoebic meningoencephalitis and granular amoebic encephalitis, are caused by free-living amoeba.
Autoimmune encephalitis
Possible symptoms of autoimmune encephalitis include psychomotor disorders, psychosis, abnormal movements, and dysautonomia. Anti-N-methyl-D-aspartate receptor encephalitis and Rasmussen's encephalitis are examples of autoimmune encephalitis. Anti-NMDA receptor encephalitis is the most common form of autoimmune disease and is associated with ovarian teratomas in 58% of women aged 18 to 45 years.
Diagnosis and testing
For the diagnosis of encephalitis, the patient is required to show decreased or altered consciousness, lethargy, or personality changes for at least 24 hours without other explainable reasons. Encephalitis is usually diagnosed using a variety of tests, including brain scans (MRI), electroencephalograms (EEG), and spinal fluid analysis.
Prevention and treatment
Some types of encephalitis can be prevented with vaccines, especially those caused by viruses. In addition, treatment usually focuses on antiviral drugs, antiepileptic drugs, and corticosteroids, usually in a hospital setting. In some cases, patients may need artificial respiration. When the acute problem is controlled, rehabilitation may be needed.
The prognosis of encephalitis depends on a variety of factors, including cerebral edema, status epilepticus, and thrombocytopenia, among other poor prognostic factors. In early diagnosis, a normal EEG predicts a higher survival rate.
Epidemiology
In Western countries, the new incidence rate of acute encephalitis is approximately 7.4 cases per 100,000 people per year. In tropical countries, the figure is 6.34 cases per 100,000 people. From 2005 to 2015, reported cases of encephalitis in the United States remained approximately stable, with approximately 250,000 cases per year.
As humans gradually deepen their understanding of the causes of encephalitis, have you also thought about how to more effectively prevent these fatal brain inflammations?
