Encephalіtіs, or infection in the brain, is a condition in which inflammation affects the parenchyma of the brain. The cause of encephalіtіs is a virus that has penetrated into the brain tissue, mainly the herpes virus, arbovirus, and enterovirus, as well as the measles virus and mumps virus. This is a very dangerous disease as it can lead to irreversible brain damage and even death. What are the causes and types of encephalіtіs? How to recognize its symptoms? What is the treatment?
Encephalitis occurs when inflammation affects the parenchyma of the brain. This disease is one of the inflammations of the central nervous system, along with inflammation of the spinal cord and meninges. It can have various causes (including viruses, bacteria, drugs), and its course can be acute (and lead to death within a few hours), subacute and chronic (then the inflammation can last for years). Vaccіne encephalomyelitis develops on an allergic background after vaccination (most often against rabies and smallpox). Acute Disseminated Encephalomyelitis (ADEM) is an autoimmune demyelinating disease of the brain, which means that the immune system attacks its cells (in this case, the brain cells). In addition, encephalіtіs can occur after ingestion of certain medications (e.g. methotrexate) or after poisoning with heavy metals (e.g. lead). Also distinguished is coma encephalіtіs (von Economo encephalitis), which is caused by an unknown pathogen.
A common feature of all brain inflammations is a high mortality.
The brain infection – causes, and types
Encephalіtіs is a rare but very serious inflammatory life-threatening disease. It can affect anyone, but children under the first year of life and the elderly are at particular risk. The causes are most often viruses, sometimes bacteria, but also non-infectious agents, e.g. autoimmune diseases.
The brain infection occurs at a frequency of 3.5–7.4 per 100,000 people. Unfortunately, it is not always possible to establish the exact cause. It is known, however, that the most common brain inflammation is caused by a viral infection. Bacterial infections and other non-infectious inflammations can also cause encephalіtіs.
Viral encephalіtіs is caused by viruses such as:
- Herpesviridae: herpesviruses (HHV-1, HHV-2; i.e. herpetic encephalitis), varicella virus (VZV), mononucleosis virus (Ebstein-Barr virus, EBV), cytomegalovirus (CMV), flushing erythema virus ( HHV-6);
- influenza virus, incl. AND;
- from the group of Polyomaviridae: John Cunningham virus (JCV, causing progressive multifocal leukoencephalopathy);
- rabies virus;
- from the group of Paramyxoviridae: measles, mumps;
- rubella virus;
- from the Flaviviridae group: West Nile virus, Japanese encephalitis virus, St. Louis, Powassan virus, Murray Valley encephalitis virus, tick-borne encephalitis virus (tick-borne encephalitis, TBE);
- California virus, La Crosse virus, or Equine encephalitis viruses (Eastern, Western, and Venezuelan).
Infections following childhood diseases – measles, smallpox, rubella, and influenza are believed to be infectious and not caused by the direct microbial invasion. These microorganisms are also indicated as the most common cause of encephalіtіs among children. The situation is different if it comes to adults, where HSV-1 is the most common etiological factor.
The bacteria causing bacterial encephalіtіs include, іn partіcular:
- Mycobacterium tuberculosis (tuberculous encephalitis);
- the Borrelia burgdorferi group (Lyme encephalitis);
- also, the more rare ones, such as Bartonella henselae, Mycoplasma pneumoniae, rickettsiae, or Legionella pneumoniae.
It is also worth remembering other infectious causes of encephalіtіs, such as parasites or fungi (Coccidioides immitis, Histoplasma capsulatum). In cases of parasitic infections, we mean the protozoa Naegleria fowleri (primary amoebic encephalitis), Toxoplasma gondii, or the Plasmodium group.
Brain infection can also accompany meningitis. The most common etiological factors, depending on age, include:
- among newborns – gram-negative bacilli (Klebsiella, E. coli, H. influenza);
- among children – H. influenza, Streptococcus pneumoniae (so-called pneumococci), and Neisseria meningitidis (so-called meningococci);
- among adults – Streptococcus pneumoniae and Neisseria meningitidis.
The non-infectious causes of encephalіtіs include autoimmune diseases, cancer, and vaccinations.
Encephalitis – symptoms
Encephalіtіs can be mild or severe. Treatment, depending on the severity of its course, can be spontaneous or aggressive. The prognosis also depends on the form of the disease. Unfortunately, severe neurological complications are possible.
The prodromal symptoms of infection in the brain are often the classic symptoms of a viral infection. After a few days, the symptoms of central nervous system involvement appear, often manifested by:
- changed mental state,
- considerable irritability and agitation,
- personality changes.
There are also seizures (focal or generalized), sometimes accompanied by signs of focal damage to the nervous system. The autonomic system and cranial nerves are damaged. Cerebellar syndrome, including dysarthria, ataxia, may also occur. Patients may become lethargic or even comatose and eventually die. There is memory impairment.
On physical examination, there may appear positive meningeal symptoms, such as a stiff neck. If it’s cerebral edema, the symptoms of increased intracranial pressure can appear.
Overall, there are such symptoms of brain infections as:
- headaches (accompanied by nausea and vomiting as well as photophobia, hypersensitivity to auditory stimuli, or skin hypersensitivity)
- disturbance of consciousness (which causes thinking and behavior disturbances)
Symptoms of focal brain damage:
- Focal symptoms are disorders of neurological functions related locally to specific areas of the brain. The most common focal features are motor symptoms (weakness or disability in one or more limbs), sensory symptoms (disturbances/loss of sensation in one or more limbs, visual disturbances, double vision), speech disorders (difficulty understanding speech, words), cognitive disorders (memory impairment, Spatio-temporal disorientation), balance disorders, and seizures. For example, coma encephalіtіs is characterized by impaired sleep-wake and double vision.
- There are also symptoms characteristic of infection with a specific pathogen. For example, encephalitis, caused by Borrelia burgdorferi, is accompanied by characteristic erythema (with a brightening in the center) migrating.
Is encephalіtіs curable?
Treatment of encephalіtіs requires hospitalization. If it is caused by a viral infection, it should be necessarily treated with antiviral drugs. They are administered intravenously in 3 weeks. They use anti-inflammatory corticosteroids as well. Treatment of the disease is also based on relieving the symptoms, especially preventing cerebral edema.
Encephalіtіs is severe and fatal but is curable. Early dіagnosіs and prompt treatment are crucial. Specific treatment exists only for the herpes virus. Other treatments are mainly symptomatic, relieving the manifestations of the disease: bed rest, temperature reduction, monitoring the water balance, anticonvulsant medicine. The neurologіcal symptoms of encephalitis may persist for a long time, so rehabilitation is also important. The disease can have lasting consequences in the form of neurological or mental disorders.
Is encephalіtіs curable?Treatment of encephalіtіs requires hospitalization. If it is caused by a viral infection, it should be necessarily treated with antiviral drugs. They are administered intravenously in 3 weeks. They use anti-inflammatory corticosteroids as well. Treatment of the disease is also based on relieving the symptoms, especially preventing cerebral edema. Encephalіtіs is severe and fatal but is curable. Early dіagnosіs and prompt treatment are crucial. Specific treatment exists only for the herpes virus.