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What is encephalitis (brain inflammation)?

Encephalitis, also called brain inflammation, is inflammation of brain tissue that can be caused by viruses, bacteria, fungi or the body's own immune system. This inflammation can affect different parts of the brain and lead to neurological or cognitive disorders, which may present as changes in behaviour or thinking.

The blood–brain barrier usually protects the brain from pathogens, but some organisms can cross this barrier and cause encephalitis. In severe cases the brain tissue may swell, resulting in permanent damage or even brain haemorrhages.

A particular form is meningoencephalitis, where the protective membranes around the brain (the meninges) are inflamed in addition to the brain itself.

What are the symptoms of encephalitis?

Symptoms of brain inflammation vary widely depending on the cause, severity, the brain region affected and the person's overall condition. General symptoms often appear first and may develop into more specific neurological signs.

Early on there are typically non-specific symptoms such as headache, high fever and flu-like symptoms like fatigue, nausea and exhaustion.

As the condition progresses, confusion and disturbances of consciousness often occur, ranging from drowsiness to coma, as well as concentration problems and short-term memory impairment. Behavioural or personality changes are common, and in some cases hallucinations may occur. Neurological deficits such as weakness or speech problems, epileptic seizures and coordination difficulties are also frequently seen.

Certain pathogens can target different brain areas and cause specific symptoms. Herpes simplex encephalitis leads to speech disturbances and seizures; arbovirus infections (viruses transmitted by insects) often cause movement disorders, and enteroviruses can trigger muscle twitches and tremors.

In autoimmune encephalitis neurological and cognitive symptoms are often prominent. Behaviour changes, concentration difficulties and movement disorders are frequent. A sudden fever spike is more suggestive of an infection than an autoimmune reaction.

Children and infants often show non-specific signs with encephalitis, such as irritability and lethargy, poor feeding, neck stiffness and fever, as well as seizures and muscle twitching.

If such symptoms occur, especially in combination, an immediate medical assessment is necessary, as early treatment is crucial for the course and prognosis of encephalitis.

What causes encephalitis?

Encephalitis is triggered by invasion of pathogens or by a misdirected immune response. The most common causes are viruses – for example the herpes simplex virus, the West Nile virus (transmitted by mosquitoes) or the TBE (FSME) virus. The latter is usually spread by ticks and can cause inflammation of the brain, meninges and/or spinal cord (tick-borne meningoencephalitis, abbreviated TBE or FSME). Influenza viruses can also rarely cause encephalitis.

There is a distinction between infectious and autoimmune encephalitis. In infectious encephalitis the trigger is an infection by viruses, bacteria or fungi. Immunocompromised or elderly people and children are particularly at risk. Vaccinations are available for many pathogens. In autoimmune encephalitis, by contrast, the immune system mistakenly attacks the brain's nerve cells, causing inflammation. Examples include anti-NMDA receptor encephalitis, where specific antibodies target nerve cells. Such autoimmune processes can be triggered by infections, cancers or, more rarely, vaccines.

Although encephalitis has many possible causes, it remains a significant health risk especially for immunocompromised people and children. Prompt treatment can, however, positively influence the course of the disease.

What is the difference between meningitis and encephalitis?

The difference between meningitis and encephalitis lies in the part of the brain affected by the inflammation. In meningitis the meninges, the protective coverings of the brain, are inflamed, whereas in encephalitis the brain tissue itself is affected, particularly the cerebral cortex.

Sometimes both areas are inflamed at the same time; this is called meningoencephalitis. This mixed form can cause both the typical symptoms of meningitis, such as neck stiffness, and the neurological symptoms of encephalitis. Meningitis can sometimes progress to encephalitis and vice versa.

What is the prognosis and what are the consequences of encephalitis?

The prognosis of encephalitis strongly depends on the course of the disease, the causative agent, the brain region involved and the patient's overall health. While a mild encephalitis often heals completely without long-term consequences, a severe encephalitis can lead to permanent damage and typically requires hospitalisation.

In about one third of cases long-term consequences remain after encephalitis, such as concentration or speech problems or even epileptic seizures, because nerve cells have been destroyed. Children may experience developmental delays and, less commonly, hydrocephalus, an abnormal accumulation of cerebrospinal fluid.

Outcomes are pathogen-dependent: while tick-borne meningoencephalitis (TBE/FSME) often does not lead to severe long-term effects, the risk of complications is higher with herpes simplex encephalitis. Untreated, the latter has a fatality rate of around 70%; however, timely antiviral treatment saves most patients.

A rare and particularly dangerous consequence is subacute sclerosing panencephalitis (SSPE), which can occur after measles infection and is almost always fatal. Overall: early treatment can substantially improve the prognosis and increase the chance of full recovery.

Can encephalitis be prevented?

One of the most important measures is protection against specific pathogens that can cause brain inflammation. There are effective vaccines for many viruses that may cause encephalitis, for example measles, mumps, rubella, chickenpox (varicella/zoster), polio, TBE (FSME) and influenza. Your doctor can advise you individually.

Before travelling it is also wise to check recommended vaccinations for the destination to minimise the risk of encephalitis from exotic viruses such as Japanese encephalitis virus or West Nile virus.

Encephalitis: when is vaccination recommended?

Vaccination against tick-borne encephalitis (TBE/FSME) is recommended for people who live in or visit risk areas, because tick bites in those regions can transmit the TBE virus. People who spend a lot of time outdoors – hikers, cyclists, campers, forestry and agricultural workers – especially benefit from vaccination. These parasites can also be present in urban parks and gardens, so protection may be advisable there too.

Primary immunisation consists of three doses: the first two doses 2–4 weeks apart provide initial protection for the current season; the third dose 5–12 months later ensures long-term protection of over 95% for at least 10 years. Booster vaccinations are recommended every 10 years.

Ideally the vaccination series starts in winter to be protected for the tick season in spring. For short-term protection, e.g. for travel to risk areas, an accelerated schedule can be used that provides immunity after a few weeks. The TBE vaccine is well tolerated; mild side effects such as redness at the injection site or fatigue occasionally occur, while severe reactions are extremely rare.

Tips: how is encephalitis treated?

• Early treatment is crucial to avoid complications and long-term damage. The sooner therapy is started, the better the chances of full recovery.
• Encephalitis always requires inpatient treatment, preferably in a specialised hospital with neurological or intensive care. Severe cases may need treatment in an intensive care unit.
• If viral encephalitis is suspected, especially due to herpes simplex or varicella-zoster viruses, treatment with aciclovir is often started immediately, even before the pathogen is confirmed. This is important because untreated herpes simplex encephalitis can be life‑threatening.
• If encephalitis is caused by bacteria, antibiotics are used; for fungal causes, antifungal agents (antimycotics) are administered.
• In autoimmune encephalitis the immune system is suppressed with high‑dose glucocorticoids (cortisone) or immunosuppressants. Immunoglobulins may be given or plasmapheresis (blood washing) performed to remove harmful antibodies from the body.
• For encephalitis forms without a specific antiviral therapy (such as TBE), treatment focuses on symptom relief, for example with painkillers and fever reduction.
• Epileptic seizures are treated with antiepileptic medications. For behavioural disturbances or psychiatric changes, antipsychotics may be prescribed temporarily to control symptoms.
• Strict bed rest and adequate fluid intake are essential for recovery. In severe cases fluids may be given intravenously to support the body.
• After the acute phase, physiotherapy, occupational therapy and speech therapy can help to improve neurological functions such as speech, motor skills or memory.
• After hospital discharge, regular follow-up is important to detect and treat late effects such as cognitive impairment or epileptic seizures early.

Encephalitis is a serious condition that can put the brain into a potentially life‑threatening state of emergency. Timely diagnosis and treatment are therefore as important as preventive measures such as vaccination and protection against tick bites. While the disease remains severe, modern medicine and early intervention mean many patients can expect a positive outcome.