How is encephalitis transmitted?

Written by Zhang Hui
Neurology
Updated on September 24, 2024
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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 Zhang Hui
Neurology
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After-effects of encephalitis

Some more serious types of encephalitis may leave sequelae. For example, common ones like herpes simplex viral encephalitis and epidemic encephalitis B. A minority of patients may suffer from certain degrees of sequelae, which typically include the following aspects. Firstly, some patients may experience secondary epileptic seizures, which present with loss of consciousness, limb convulsions, incontinence, and frothing at the mouth. These symptoms might require long-term oral medication for epilepsy. Secondly, another consequence of encephalitis is cognitive impairment in patients, characterized by significant reductions in computational ability, memory, and executive function. Additionally, some forms of encephalitis might leave patients with psychiatric symptoms, such as speaking incoherently.

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Written by Zhang Hui
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Viral encephalitis and bacterial encephalitis differences

There are significant differences between viral encephalitis and bacterial encephalitis in clinical settings. Firstly, their clinical symptoms differ; the fever in viral encephalitis is generally lower than that in bacterial encephalitis, where there may be widespread chills and persistent high fever. From another perspective, laboratory tests also help differentiate the two. In viral encephalitis, a routine blood test shows no increase in white blood cells, mainly an increase in the proportion of lymphocytes. In contrast, bacterial encephalitis is characterized by a significant increase in white blood cells, which aids in distinguishing the two. Furthermore, an essential diagnostic tool is the lumbar puncture, through which cerebrospinal fluid can be tested. In viral encephalitis, the white blood cell count in the cerebrospinal fluid is slightly increased; in bacterial encephalitis, it is significantly increased. The cerebrospinal fluid in viral encephalitis has a slight increase in protein content with no significant change in chloride levels; however, in bacterial encephalitis, the protein content in the cerebrospinal fluid is notably higher, and there is a significant decrease in chloride levels.

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Neurology
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How is encephalitis diagnosed?

The diagnosis of encephalitis relies on the following aspects. First, it is based on clinical manifestations. If the patient clearly exhibits symptoms such as headache, fever, nausea, vomiting, and signs of increased intracranial pressure, and physical examination shows positive signs of meningeal irritation, then there is a high suspicion of encephalitis. Second, various auxiliary tests can be conducted. Initially non-invasive tests such as electroencephalograms (EEG) and magnetic resonance imaging (MRI) of the skull can be completed. If the MRI reveals significant abnormalities, such as abnormal signals in the frontal and temporal lobes including the hippocampus, then viral encephalitis should be highly suspected. If the EEG shows moderate abnormalities or increased slow waves, it also indicates damage to the cerebral cortex, serving as an indirect indicator of encephalitis. Third, a lumbar puncture can be performed to ascertain any abnormalities in the cerebrospinal fluid (CSF) routine and biochemical tests. If the cell count is elevated beyond ten times the normal value, an inflammatory infection is considered. There is often a minor to moderate increase in protein. The levels of glucose and chloride may decrease in bacterial and tuberculous encephalitis, while they are generally normal in viral encephalitis.

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What is checked for encephalitis?

The examination items for encephalitis mainly include, first, some basic hematological tests. These include routine blood tests, liver and kidney function tests, electrolytes, etc., to understand the status of the patient's white blood cells and whether there is any damage to liver and kidney functions. It is also necessary to test for cardiac enzymes, as some viruses can also affect the heart. Second, an EEG is required. Abnormal EEG patterns, such as increased diffuseness, can be observed in encephalitis, which is important for accurate diagnosis. Third, further examinations like lumbar puncture and cerebrospinal fluid tests are needed. The main focus in cerebrospinal fluid is to see if there is an increase in white blood cells and to check if there are any changes in protein and sugar levels in the fluid. This has great reference value for diagnosing whether it is encephalitis and what type of encephalitis it might be. Fourth, a cranial MRI can be performed to clearly identify if there are any organic lesions in the brain.

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Is encephalitis serious?

The severity of encephalitis varies greatly among individuals. Some mild cases of encephalitis, even with some degree of self-healing, do not require special treatment. For example, encephalitis caused by some enteroviruses and respiratory viruses has a very good recovery, and it is only necessary to prevent complications. However, some types of encephalitis are very dangerous and can even threaten the life of the patient. For instance, herpes simplex virus encephalitis can cause necrosis of the cerebral cortex, leading to high fever, headache, nausea, vomiting, and even epileptic seizures, psychiatric symptoms, and a significant increase in intracranial pressure, requiring urgent treatment.