How is encephalitis caused?

Written by Tang Li Li
Neurology
Updated on September 13, 2024
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Encephalitis generally falls into two categories: one is infectious inflammation caused by pathogenic infections, and the other is immune inflammation caused by abnormalities in immune mechanisms. Among these, the infectious type is the most common, including viral encephalitis, viral meningitis, tuberculous meningoencephalitis, purulent meningitis, and cryptococcal meningitis, which are associated with infections by viruses, bacteria, Mycobacterium tuberculosis, and Cryptococcus, respectively. Additionally, abnormalities in the immune system often cause autoimmune encephalitis, as well as multiple sclerosis and neuromyelitis optica when involving the brain, and acute disseminated encephalomyelitis, all of which are types of autoimmune encephalitis. The treatment approaches for these two types of encephalitis are different. For pathogen-induced cases, treatment primarily targets the pathogens: antiviral drugs for viral encephalitis, antibiotics for bacterial encephalitis, anti-tubercular therapy involving multiple drugs for Mycobacterium tuberculosis infection, and antifungal drugs, such as amphotericin B, for cryptococcal meningitis. For immune-mediated encephalitis, treatments generally involve immunosuppressants, high-dose corticosteroids, or intravenous immunoglobulins.

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Written by Zhang Hui
Neurology
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How is encephalitis transmitted?

The commonly mentioned encephalitis is mainly caused by viral infections. There are many types of viruses that can cause encephalitis, including the more severe herpes simplex virus, varicella-zoster virus, etc. There are also some enteroviruses, like Coxsackie virus, and some adenoviruses. Typically, the transmission of encephalitis can occur via the fecal-oral route, where some enteroviruses enter the digestive tract through this route, then from the cells of the digestive tract to the bloodstream, and from there to the brain. Additionally, some viruses are transmitted through blood contact. For instance, if a patient has blisters that rupture and release a large amount of virus, and another person's blood comes into contact with these fluids, transmission can occur via blood. Generally, encephalitis is primarily transmitted through fecal-oral routes and bloodborne transmission.

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Written by Tang Li Li
Neurology
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How is encephalitis in children diagnosed?

If a child presents with fever, headache, nausea, vomiting, or even convulsions and seizures, it is necessary to be vigilant about the possibility of encephalitis. It is advised to seek medical attention in pediatrics or neurology to conduct a thorough examination. First, an MRI of the brain should be carried out to observe if there are any abnormal signals in the meninges or any damage within the brain substance. Second, cerebrospinal fluid analysis via lumbar puncture is essential for diagnosing encephalitis, as encephalitis patients often show significant abnormalities in cell count and biochemistry of the cerebrospinal fluid, allowing for the identification of different types of infections. Third, an electroencephalogram (EEG) is conducted. While EEG specificity is not high, an affected cerebral cortex in encephalitis patients will show abnormal slow waves. Fourth, routine tests such as a complete blood count should be performed; an elevated blood count can indirectly indicate a potential infection in the patient.

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Written by Zhang Hui
Neurology
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What are the symptoms of encephalitis?

The clinical manifestations of encephalitis are complex and varied, primarily caused by infections from pathogens such as viruses and bacteria. There are numerous clinical symptoms, with fever being quite common; patients generally exhibit significant fevers, which can reach up to 38 degrees Celsius or even as high as 40 degrees Celsius. Headache is also a very common clinical manifestation of encephalitis, with some patients experiencing severe headaches accompanied by pronounced nausea and vomiting. Additionally, some patients may exhibit psychiatric symptoms, which mainly include incoherent speech, hallucinations, and failing to recognize family members. Some patients may experience cognitive impairments, such as diminished memory, and significant deficits in computational and judgment abilities. In severe cases, some patients may have epileptic seizures, characterized by convulsions of the limbs. Overall, the manifestations of encephalitis are diverse and can range from simple fever and headache to severe conditions such as psychiatric symptoms, cognitive impairments, and epilepsy.

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Written by Zhang Hui
Neurology
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Encephalitis belongs to which department?

Encephalitis is primarily a neurological disorder and is an infectious disease of the central nervous system, mainly diagnosed and treated in neurology. There are many causes of encephalitis, with viral encephalitis being the most common. For example, herpes simplex encephalitis is a typical type seen clinically. Patients may experience fever, even with very high temperatures exceeding 40°C, headaches, nausea, and vomiting. If the condition worsens, seizures, coma, and cognitive impairment may occur. These clinical manifestations require further investigations like electroencephalography, cranial MRI, and lumbar puncture. Additionally, there is a specific type of epidemic, known as Japanese encephalitis, which falls under the category of infectious diseases due to its contagious nature.

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Written by Zhang Hui
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How is encephalitis caused?

Encephalitis generally occurs when pathogens invade the central nervous system of the brain, resulting in corresponding clinical manifestations. Patients may exhibit symptoms such as headache, fever, nausea, vomiting, and even paralysis of limbs and cognitive impairments. Patients become confused, with reduced computational and comprehension abilities. Some may also exhibit psychiatric symptoms and even experience seizures and other manifestations of epilepsy. Encephalitis is caused by pathogens, commonly viruses. Viral infections that lead to what is known as viral encephalitis can spread through the bloodstream to the brain and cause illness. Additionally, bacterial infections can also cause encephalitis. There are mainly two routes for bacterial infections: one is through bloodstream transmission leading to inflammation of the nervous system, and the other can occur directly, for example, from inflammation of the mastoids, tonsils, or cavernous sinus, where bacteria directly invade the brain, leading to the respective clinical manifestations. Furthermore, tuberculosis can also infect and cause tuberculous encephalitis, meningitis, and similar conditions.