Encephalitis (inflammation of the brain)

Encephalitis is an inflammation of the brain. If the brain inflammation occurs in conjunction with meningitis or inflammation of the meninges (the protective lining of the brain and spinal cord), this is known as meningoencephalitis.

Encephalitis is most commonly caused by a viral infection. Herpes simplex viruses are frequently responsible.

Auto-immune responses can also play a role in the development of this condition. These are inappropriate responses of the immune system that attack and damage the body’s own tissues. This type of encephalitis is called auto-immune encephalitis.

Encephalitis may cause impaired consciousness, as well as changes to behavior and personality. Individual brain function may also fail and epileptic seizures may occur.

The condition can be mild but also may be life-threatening and cause severe, long‑term effects.

The most common symptoms of encephalitis are:

• confusion
• headache
• seizures
• impaired consciousness
• fever

Changes in behavior, hallucinations and cognitive impairment are also possible.

Different symptoms may occur depending on which virus is causing the inflammation:

• Infection with herpes simplex viruses often causes speech disorders, such as aphasia.
• Arboviruses, which are transmitted by insects, more commonly cause movement disorders.
• If a person is infected with an enterovirus with serotype EV 71, they may experience shaking, muscle twitches, impaired movement and paralysis.

Other neurological symptoms may also occur, such as paralysis of one side of the body, flaccid paralysis of individual muscle groups, or numbness.

Sometimes, the disturbance of brain functions is so mild that it is barely noticeable.

Newborn babies and infants show symptoms of encephalitis that are of a more general nature – they don’t drink well and are listless and lethargic. They may also experience fever and cramps.

Encephalitis can be caused by viruses, bacteria, fungi or parasites, such as worms or toxoplasma. Such cases of encephalitis are known as infectious encephalitis.

Alternatively, encephalitis may be auto-immune encephalitis, in which the immune system develops antibodies that attack and damage the body’s own brain cells. These antibodies are known as autoantibodies.

Approximately 70 percent of cases of encephalitis are caused by viruses. The most common of these are:

• Herpes simplex viruses, which cause oral herpes (cold sores) and genital herpes, for example
• Enteroviruses, which cause hand, foot and mouth disease, for example
• Epstein-Barr viruses, the pathogens responsible for glandular fever
• Cytomegalovirus (CMV)
• Varicella-zoster viruses, the pathogens that cause chickenpox and shingles
• Parechoviruses, which cause respiratory and gastrointestinal infections
• Influenza viruses, which cause flu
• Arboviruses, which are transmitted by ticks and mosquitoes, such as the pathogens that cause tick-borne encephalitis (TBE) or West Nile Virus.

Encephalitis is sometimes caused by infections with measles, mumps and rubella viruses or, more rarely, by a SARS-CoV-2 infection.

Auto-immune encephalitis may occur as a result of cancer. In this case, the brain is attacked by immune cells that the body has activated against tumor cells.

The prevalence of encephalitis differs depending on the cause. Every year, around 4 to 8 people in every 100,000 develop viral encephalitis. Childhood encephalitis affects about 4 to 10 children in every 100,000 and occurs most commonly during the first year of life.

There is also a seasonal variation in some types of viral encephalitis. Tick-borne encephalitis (TBE), which is widespread in Europe, occurs in early summer when ticks, which carry the disease, are especially active. The same applies to brain inflammations caused by pathogens that are spread by mosquitoes – such as West Nile virus.

In many cases, inflammation of the brain heals without any lasting effects.

Long-term effects occur in around one third of cases. The most common of these are seizures, impaired concentration, behavioral issues, and difficulties with memory or language that are difficult to treat.

Around one percent of people continue to suffer massive functional impairment of the brain with a persistent impairment of consciousness after the inflammation has healed.

Around one third of all children who develop encephalitis experience long-term limitations. Depending on the nature of the encephalitis, these can include developmental disorders, learning difficulties, or behavioral problems. Muscle movement, vision, hearing, or urination is sometimes also impaired.

Several vaccines are available that target possible causes of brain inflammation. In many cases, these vaccines are recommended by STIKO, the Standing Committee on Vaccination in Germany, as they offer protection from the serious long-term consequences of encephalitis.

For information about vaccination recommendations and how vaccines work, see our article on the topic of vaccinations. 

Some brain inflammations are caused by pathogens that can be targeted directly with medication.

For this reason, it’s important to pinpoint the precise cause. To narrow down the possibilities, doctors will ask the patient for information, for example, about:

• their general health
• any medication they require
• prior vaccinations
• recent travel

Symptoms such as skin rashes, swollen lymph nodes, memory and language impairments or certain movement disorders may point to a specific pathogen.

CT (computed tomography) or MRI scan (magnetic resonance imaging) can be used to scan sections of the brain to detect inflammation. The site of the inflammation in the brain can indicate its cause in some cases.

Doctors can also take a sample of liquor, i.e., cerebrospinal fluid, from the spinal canal in the spine if encephalitis is suspected. This is the fluid surrounding the brain and spinal cord. In the liquor, pathogens can be detected directly by means of genetic analysis or via the antibodies that target specific pathogens. Certain autoantibodies will be found in the liquor if the person has auto-immune encephalitis.

A blood sample similarly enables the detection of antibodies that are produced in response to specific pathogens. If the person is having seizures, doctors can examine the activity patterns in the brain using an electroencephalogram (EEG).

For many types of viral encephalitis, there is no specific treatment to target the precise cause. In these cases, treatment is therefore limited to measures to relieve symptoms.

One exception is encephalitis caused by herpes simplex viruses. This type of brain inflammation can have severe consequences if left untreated. Long-term effects can be avoided if the medication aciclovir is administered at an early stage. For this reason, patients are usually given aciclovir even before the exact pathogen that has caused the encephalitis has been identified.

Aciclovir and similar active agents are also used to treat brain inflammations caused by the varicella-zoster virus or cytomegalovirus.

Seizures are treated with medication. Medication may also be used on a temporary basis to treat behavioral disturbances.

Non-viral encephalitis must be treated in accordance with its cause. If it is suspected that the encephalitis is bacterial, antibiotics are used at an early stage.

People with auto-immune encephalitis are given high-dose corticosteroids, which have an anti-inflammatory effect. Doctors also have the options of using blood plasma exchange (plasmapheresis) and drugs that suppress the immune system (immunosuppressives). These are aimed at preventing further damage by antibodies.