Introduction
When there is an inflammation in the brain, different areas can be affected. If the inflammation is in the brain itself, it is called encephalitis. If the meninges surrounding the brain are affected, the inflammatory change is called meningitis.
It is also possible for both areas to fall ill together. This is called meningoencephalitis. Triggers for such a disease are bacteria, viruses, fungi and other parasites.
Causes
In most cases, bacteria or viruses are the cause of an inflammation in the brain. Infection by fungi or other parasites is less frequent, but still possible. The pathogens penetrate the body in different ways.
One can mainly distinguish between the following possibilities:
- After infection of the nasopharynx, the germs are carried via the bloodstream to the brain (haematogenic spread) and settle there;
- After a sinus, ear or eye infection, the pathogens penetrate deeper into the tissue up to the brain and establish themselves there;
- Through a head or spinal column injury, the central nervous system comes into direct contact with the disease-causing (pathogenic) germs.
Which pathogens cause the inflammation in the brain depends on various factors. The patient’s age and state of health are very important. An infestation with fungi or other parasites is more common in the group of immunocompromised persons.
Infection with Cryptococcus neoformans (yeast fungus – crytococcosis), Toxoplasma gondii (protozoan – toxoplasmosis) or Cysticercus cellulosae (tapeworm – cysticercosis) is often the cause of the disease. Causes of meningitis: The causative agents of bacterial meningitis are most easily classified according to the age of the patients. Newborns are most frequently attacked by Escherichia coli, B streptococci (usually Streptococcus agalactiae) or Listeria (Listeria monocytogenes).
In some cases, this occurs already during delivery in the birth canal, later by the mother or nursing staff or by contaminated food. Children and adolescents have an increased risk of contracting Haemophilus influenzae type B, to which adults are usually already immune. From childhood to adulthood, meningococcus (Neisseria meningitidis) and pneumococcus (Streptococcus pneumoniae) are the main causes of bacterial inflammation of the meninges.
Bacterial meningitis pathogens that cause specific clinical pictures are Treponema pallidum (neurosyphilis), Leptospira icterohaemorrhagica (Weil disease) and the tick-borne Borrellia burgdorferi (neuroborreliosis). The most common viral pathogens of meningitis are various enteroviruses, various herpes viruses, the mumps virus and the flavivirus, which is mostly transmitted by ticks and causes TBE (early summer meningoencephalitis). Causes of encephalitis: An inflammation inside the brain is mainly caused by viruses.
Bacterially caused encephalitis is usually the result of a preceding meningitis – meningoencephalitis then exists. Most encephalitides are caused by the outbreak of herpes simplex virus I in the body. More than 90% of the population carries this virus, sometimes unknowingly.
After a single infection, usually in childhood, it settles in nerve nodes (spinal ganglia) of its host and remains there until the end of its life. If the immune system is weakened, the virus can break out and cause herpes simplex encephalitis. Other relevant virus strains are the varicella zoster virus (chickenpox, shingles), the cytomegalovirus, the measles virus, the rubella virus, the influenza virus (flu), HIV and the rabies virus.
Stress alone cannot lead to an inflammation of the brain, a so-called encephalitis. However, herpes viruses that are activated by stress can lead to such an inflammation of the brain. Herpes viruses have the peculiarity that after an initial infection, such as chickenpox, they hide in certain nerve cells of the affected person and cannot be eliminated by the immune system.
However, they are inactive at this stage. If these viruses are reactivated by various triggers, such as stress, they can lead to different symptoms. These range from the development of individual herpes blisters on the lip to the rare inflammation of the brain, which is then called herpes encephalitis and can lead to death if left untreated. In most cases, however, an inflammation of the brain is not the first sign of reactivation of the viruses.In most cases, shingles and lip herpes, for example, develop before the viruses spread to the brain. Herpes encephalitis should be considered if such initial manifestations are present and neurological deficits develop.
