Encephalitis

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Encephalitis is inflammation (swelling) of the brain tissue. It is caused either by infection, usually viral, or by an autoimmune disease. An autoimmune disease is when your immune system tries to fight off an infection but by mistake, attacks parts of your body at the same time.

Some people who have encephalitis are left with permanent brain damage. The type and degree of brain injury can vary.

In most cases, a viral infection does not lead to encephalitis; only extremely rarely does a virus directly attack the brain and cause Infectious Encephalitis.

Viruses may also directly attack the linings of the brain (meninges) and cause meningitis. Encephalitis is more serious than meningitis, because it affects the brain itself. If the meninges are inflamed as well as the brain, the condition is called meningoencephalitis.

Encephalitis can affect anyone in any part of the world, at any age but it is extremely rare, with approximately 4 in every 100,000 affected in the UK each year.

Encephalitis can happen suddenly and cause serious problems to the nervous system and the brain. Some viruses have the ability to affect nerves and damage the central nervous system. The central nervous system is made up of the brain, spinal cord and nerves within the skull and spine. The peripheral nervous system is a group of nerves that connects the brain and spinal cord to the rest of the body.

Some types of encephalitis can be mild and cause almost no symptoms, other than feeling ill with a fever, but other cases can be very serious and life threatening.

The viruses that cause encephalitis are often common viruses and can be contracted through insect and animal bites, food, or direct infection.

Although viruses infecting the brain are a major cause of encephalitis, the bodyâ€™s reaction to infection itself can occasionally lead to encephalitis. This can happen if your immune system tries to fight off the infection and by mistake, attacks the nerves in the brain at the same time. This condition is called Post Infectious or Autoimmune Encephalitis.

If the meninges are inflamed as well as the brain, the condition is called meningoencephalitis.

If the spinal cord is inflamed as well as the brain, the condition is called encephalomyelitis.