October 26, 2024, 12:40 pm | Read time: 5 minutes

Loss of consciousness, loss of speech, paralysis, and even personality changes: Encephalitis can manifest itself through various warning signs – and can have many causes. FITBOOK explains.

In encephalitis, viruses, bacteria, parasites, or protozoa invade the brain and cause inflammation. For example, herpes viruses or the tick-borne encephalitis virus can trigger encephalitis. However, the immune system can – rarely – also be responsible for the inflammation. If left untreated, encephalitis can lead to long-lasting or permanent brain damage. Unfortunately, deaths still occur.

What are the causes of encephalitis?

There are many possible causes of encephalitis. The invaders that trigger inflammation of the brain can come from outside, for example, in the form of viruses, bacteria, parasites, fungi, or protozoa. Herpes viruses or the tick-borne TBE virus (abbreviation for tick-borne encephalitis) can trigger an inflammation of the brain. The number of registered cases of tick-borne encephalitis in the EU in 2022 was 3432.

In the case of TBE, infections with the viruses are asymptomatic. The risk of severe disease is significantly higher in people over 60 years of age.

Japanese encephalitis

The most prevalent form of viral encephalitis in the Asia-Pacific region is Japanese encephalitis, which is caused by the Japanese encephalitis virus (JEV). The virus is transmitted by Culex mosquitoes. The time from the bite to the onset of the disease is five to 15 days^.1 Only around one in 250 infected people develop a severe form of the disease, which can lead to death^.2

According to the German Society for Tropical Medicine, JEV is currently only endemic in Asia and the Western Pacific. Vaccination is recommended for travel to current outbreak areas; information on this is available from the Robert Koch Institute^.3 According to the Federal Foreign Office, the frequency of infection among travelers can hardly be estimated – however, in the local population, this infection is believed to be the most common cause of death among children with meningitis.

Autoimmune encephalitis

In rare cases, the cause of encephalitis is not an infection but a misdirected immune response. This is referred to as autoimmune encephalitis. “In this form of inflammatory brain disease, the body’s own defenses are activated without an intruder being at the door,” explains neurologist Prof. Dr. Frank Erbguth to FITBOOK. The body, therefore, reacts to an external enemy that is not even there. As a result, autoantibodies are formed against the body’s own nervous system. This form of encephalitis was described for the first time in 2007. The exact cause of this antibody development is still unclear in most cases.

According to the German Brain Foundation, autoimmune encephalitis occurs five to ten times per million people. In some patients, cancer is the cause. The most common form of autoimmune encephalitis is NMDA receptor encephalitis. Other forms are characterized by antibodies against LGI1, Caspr2, GABA(A) or GABA(B) receptors, AMPA receptors, mGluR5, GFAP, or IgLON5^.4 The disease can also occur after viral infections such as influenza or mononucleosis.

Symptoms – how can you recognize encephalitis?

The range of symptoms of encephalitis is broad. “For example, if there is inflammation in the speech center in the left hemisphere of the brain, you have speech disorders,” explains Erbguth. If the motor center on the right side of the brain is affected, paralysis of the left leg can occur.

According to the expert, an alarm signal for encephalitis is a change in character: Affected persons become introverted within a very short time. Psychological changes can be observed in a relatively large number of patients: Some are depressed, others hear voices or hallucinate. Changes in speech are also often a sign of encephalitis. Those affected cannot think of words.

The deeper the inflammation penetrates, the more the brain is affected. In contrast to meningitis, those affected by encephalitis have symptoms of loss of brain function, explains neurologist Prof. Frank Erbguth.

Possible signs of encephalitis at a glance:

• Confusion
• Speech disorders
• Changes in character
• Hallucinations
• Sensitivity to light
• signs of paralysis
• Headache (also meningitis)
• Fever (also meningitis)
• Stiff neck (also meningitis)

Important to differentiate: Meningitis does not cause any impairment of brain function.

Who is affected, and when should you see a doctor?

In addition to severe viral infections and cancer, seasonal and genetic factors appear to play a role. According to the German Brain Foundation, preventable risk factors, such as a connection with diet or physical activity, are not yet known^.1

Encephalitis can affect anyone. It cannot be prevented, only reacted quickly to. If you experience mental changes or signs of paralysis in combination with a fever, you should consult a doctor immediately.

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Therapy

According to neurologist Frank Erbguth, whether encephalitis caused by external triggers can be treated depends largely on the pathogen. He explains this using two examples: “If it is a herpes virus, you cannot prevent it, but you can treat the virus effectively.” The opposite is the case with TBE: here you can’t fight the virus directly, you can only alleviate the symptoms. There is a vaccination against TBE.

For autoimmune encephalitis, however, the approach is to remove antibodies from the blood and prevent the production of new antibodies through medication. In any case, a prompt response is crucial: The German Brain Foundation states that early treatment can often favor recovery. However, slight impairment of memory, concentration, or impulse control may remain.