Brief overview
- What is encephalitis? An inflammation of the brain. If the meninges are also inflamed, doctors call it meningoencephalitis.
- Causes: Mostly viruses (e.g., herpes viruses, TBE viruses), less commonly bacteria, fungi, parasites or an autoimmune disease.
- Diagnosis: Initially on the basis of questioning, physical examination, magnetic resonance imaging (MRI), computer tomography (CT), electroencephalography (EEG). After analysis of blood and cerebrospinal fluid, pathogens can be clearly determined.
- Treatment: Depending on the trigger, e.g. in the case of viral encephalitis, viral drugs (virustatics) via infusion; additionally symptomatic treatment (antipyretics and painkillers).
Encephalitis: Description
Encephalitis is the medical term for inflammation of the brain. This is usually caused by viruses. However, encephalitis can also be caused by other pathogens such as bacteria, fungi or parasites. In rare cases, the patient’s own defense system attacks healthy brain tissue (autoimmune reaction).
In most cases, the inflammation is acute, meaning that the disease breaks out quickly and progresses rapidly. However, there are also chronic brain inflammations, such as subacute sclerosing panencephalitis (SSPE) and progressive rubella panencephalitis (PRP). They occur virtually only in children and adolescents and are not curable. Autoimmune encephalitis also usually develops more slowly than acute cases.
Encephalitis: symptoms
Patients often initially have general, flu-like signs of illness such as fever, headache, fatigue, muscle aches and nausea. Subsequently, the specific symptoms of encephalitis develop. Symptoms include:
- Impaired consciousness (e.g., loss of consciousness or confusion).
- Sudden impairment of concentration and memory.
- Vomiting
- Neurological deficits (e.g., disturbances of speech, language, smell and/or taste, restrictions of eye movement, paralysis of individual extremities)
- Seizures
- If the meninges are also inflamed (meningoencephalitis): painful stiffening of the neck and/or back (meningismus)
In case of warning signs such as sudden high fever with nausea, headache, and impaired consciousness, have yourself taken to the hospital immediately!
Encephalitis: Causes and risk factors.
Encephalitis is usually caused by viruses. Often, the viruses first infect another part of the body and trigger an illness such as rubella, measles, mumps, or three-day fever. Later, the viruses then enter the brain.
In Germany, encephalitis occurs mainly due to the following viruses:
- Herpes simplex viruses
- Varicella zoster viruses
- Ebstein-Barr viruses
- Measles viruses
- Mumps viruses
- Rubella viruses
- Enteroviruses
- TBE (early summer meningo encephalitis) viruses
Worldwide, there are other viruses that are possible causative agents of encephalitis:
- Lyssaviruses (rabies)
- West Nile viruses
- Arboviruses (Japanese encephalitis)
- Zika viruses
- Ebola viruses
Encephalitis – Infection
But other transmission routes are also possible: TBE viruses (the causative agent of early summer meningoencephalitis) are transmitted to humans through tick bites. Animal bites (e.g. from bats) can infect people with lyssaviruses that cause rabies. In (sub)tropical areas, mosquitoes often contribute to the spread of encephalitis-causing viruses. Infection via infected blood is also possible.
Other causes of encephalitis
- Bacteria (e.g. the pathogens of syphilis, tuberculosis or Lyme disease)
- Parasites (e.g. worms or the pathogens of toxoplasmosis)
- Fungi
- autoimmune diseases (e.g. multiple sclerosis)
Bacteria reach the brain either through the blood (for example, in the case of a previous inflammation in the head), through the skin (for example, through a skin furuncle on the head), or directly (for example, during surgery on the head).
Special case: European sleeping sickness (encephalitis lethargica)
A brain inflammation whose cause is currently still unclear is the so-called European sleeping sickness (encephalitis lethargica). It occurred mainly between the years 1917 to 1927 worldwide. Affected persons are very sleepy and suffer from movement disorders similar to Parkinson’s disease.
Note: The disease should not be confused with African sleeping sickness (tryponosomiasis). It is caused by parasites that enter the body through bites of tsetse flies. However, encephalitis is also typical of the second stage of the disease.
Risk factors for encephalitis
Encephalitis: examinations and diagnosis
To diagnose encephalitis, the physician asks about the patient’s symptoms and medical history. In doing so, he asks both the patient and his relatives (external anamnesis). This is necessary because persons with encephalitis have only limited ability to think, perceive and communicate. Among other things, the physician inquires about typical complaints such as headaches and high fever. In addition, he asks further questions, such as:
- Have you recently had a viral infection?
- Were you stung by an insect?
- Were you on a vacation trip?
- Have you had contact with people with encephalitis?
Blood and cerebrospinal fluid examinations
If the physician suspects encephalitis, he or she draws blood and cerebrospinal fluid (CSF) from the patient. The cerebrospinal fluid flows through the brain and spinal cord and may contain some of the pathogens. The physician obtains a sample of this fluid by means of a lumbar puncture. This involves inserting a needle into the patient’s spinal canal at the level of the lumbar spine.
Imaging
The doctor also performs an magnetic resonance imaging (MRI) scan of the head to rule out other brain diseases, such as a brain hemorrhage or brain abscess. Sometimes he also does a computed tomography (CT) scan. However, this usually only shows visible changes as the disease progresses.
In addition, the doctor performs an electroencephalography (EEG). This enables him to determine at an early stage whether and how the inflammation is affecting brain function. In exceptional cases, he also determines the pathogen through the EEG.
Encephalitis: Treatment
Treatment of infectious encephalitis
If an inflammation caused by bacteria cannot be ruled out at an early stage, the doctor additionally administers various antibiotics (drugs against bacteria) – also directly into the vein. Only when the cause of the brain inflammation has been clearly established does the doctor discontinue unsuitable agents and, if possible, administer drugs that specifically target the pathogen.
Treatment of autoimmune encephalitis
In some cases, this treatment is not sufficient against autoimmune encephalitis. Doctors then administer other drugs that slow down the immune system, such as rituximab or cyclophosphamide. If a cancer triggers the autoimmune reactions, the cancer therapy in question may also help.
Symptomatic treatment of encephalitis
Encephalitis: course of the disease and prognosis
The chances of recovery from encephalitis depend on the severity of the illness, the pathogen that caused it, and how quickly treatment is initiated. It is important to take warning signs such as sudden high fever with nausea, headache and impaired consciousness seriously and to have them clarified immediately in the hospital.
Germs that rarely occur in Europe are also particularly problematic. These include the pathogens of rabies, Japanese encephalitis and West Nile disease. There is no specific treatment against them. They are more often fatal (rabies almost always) or cause permanent brain damage.
With an underlying autoimmune disease, the prognosis of encephalitis is predominantly good.
Complications
Encephalitis can be complicated if, for example, a seizure persists (status epilepticus) or swelling of the brain develops (cerebral edema). These complications are potentially life-threatening.
Encephalitis: Prevention
This includes vaccination against TBE for residents of areas where TBE viruses are frequently transmitted by ticks (TBE areas). It is also advisable for travelers to Southeast Asia to be vaccinated against Japanese encephalitis if they plan to stay there for a longer period of time or travel to rural areas.
