How is encephalitis caused?

Written by Zhang Hui
Neurology
Updated on September 18, 2024
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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.

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Written by Tang Bo
Neurology
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How is a brain encephalitis puncture performed?

The encephalitis you mentioned is considered a central nervous system infection. In this case, a definitive diagnosis requires a lumbar puncture, which you referred to as a puncture. The lumbar puncture requires the patient to be in the lateral recumbent position, then the puncture is performed in the interspaces between L1-L3 or L4-L5 on the back to collect cerebrospinal fluid and conduct tests. This also allows for the examination of pathogens and pressure measurements. After the lumbar puncture, the patient needs to lie flat for six hours with a pillow removed to prevent headaches due to low cranial pressure.

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Written by Zhang Hui
Neurology
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How is encephalitis diagnosed?

The diagnosis of encephalitis cannot rely solely on auxiliary examinations; it must depend on the patient's medical history, clinical manifestations, and corresponding physical examination. If a patient presents with fever, headache, nausea, vomiting, and signs of nuchal rigidity upon examination, the possibility of encephalitis should be considered. Additionally, severe cases of encephalitis may exhibit seizures, cognitive changes, and personality alterations. Auxiliary examinations mainly include three types: the first type is imaging studies, primarily brain MRI, which can clearly identify the specific areas of the brain affected and determine which brain lobe is damaged. The second important examination is an electroencephalogram (EEG), which can detect diffuse slow waves, especially a significant presence of delta waves, highly indicative of encephalitis. The third important auxiliary examination is lumbar puncture for cerebrospinal fluid analysis; an increase in white blood cells and protein in the cerebrospinal fluid also suggests inflammation within the skull. Therefore, the main auxiliary examinations for encephalitis include MRI, EEG, and lumbar puncture.

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Written by Zhang Hui
Neurology
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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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Written by Zhang Hui
Neurology
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Does encephalitis require hospitalization?

The severity of encephalitis can vary greatly; it is generally caused by viral infection. Among these viruses, Herpes Simplex Virus (HSV) is particularly dangerous. Encephalitis caused by HSV can be very severe, with symptoms including high fever, headache, nausea, vomiting, and other serious manifestations. Some patients may even experience seizures, coma, cognitive decline, and changes in mood and behavior. This type of encephalitis is very severe and definitely requires hospitalization. Typically, hospitalization lasts about 2 to 3 weeks, and proper antiviral treatment is necessary. Additionally, there are other forms of encephalitis caused by different viruses that are relatively milder and may even have a certain degree of self-healing properties. Generally, resting well, drinking plenty of water, and consuming fresh vegetables and fruits can lead to recovery. Therefore, whether hospitalization is necessary for encephalitis depends on the severity of the condition and the assessment of which virus has caused the infection. It cannot be generalized.

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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.