Encephalitis | Symptoms & Causes

What are the symptoms of encephalitis?

Your child’s symptoms may depend on the situation — the part of the brain that is inflamed, the cause of the inflammation, the degree of inflammation, age and other medical problems. But even children in the same situation may show symptoms differently. Some of the most common symptoms of encephalitis may include:

  • fever
  • headache
  • sensitivity to light
  • neck stiffness
  • skin rashes
  • nausea/vomiting
  • loss of energy/appetite
  • changes in alertness (sleepiness)
  • confusion or hallucinations
  • difficulty talking
  • problems walking
  • seizures

Since encephalitis is often caused by a virus, you may notice symptoms appear alongside or following other symptoms of a virus, such as an upper respiratory infection (like a cold, sore throat), or a gastrointestinal problem like diarrhea, nausea, vomiting or rash.

What causes encephalitis?

Encephalitis means that the brain tissue has become inflamed, and this can be caused by different things:

  • It can be the normal (and healthy) reaction of the body to a viral or bacterial infection.
  • It can be the immune system over-reacting to an infection that might not even be still present in the body.
  • It can have an auto-immune cause (the body’s immune cells become confused and start to attack healthy tissue) and occur without an infection of any kind.

Where you live might also play a role. For example, in New England, the West Nile virus is the most common mosquito-born viral cause of encephalitis.

Viruses and other infectious agents

There are some viruses that we know can cause encephalitis:

  • Herpes simplex virus: This is a common cause of encephalitis. Most children have been exposed to this virus, and your child may be infected with it even if they do not have a cold sore or blister around their mouth, or other sign of the virus.
  • Enteroviruses: These viruses enter the body through the gastrointestinal tract and can also cause hand-foot-mouth disease
  • Measles, mumps, rubella and chickenpox viruses: Keeping your child up-to-date with their vaccinations greatly lowers the rate of encephalitis from these viruses.

Other times, we may find signs in your child’s blood or spinal fluid (such as an increased white blood cell count) that their body is battling a virus or other infection that may be causing the encephalitis, even if we don’t know which particular one it is.

Encephalitis can also occur following infection by agents carrying diseases, including ticks (Lyme disease), mosquitos (West Nile virus), and cats (Bartonella, otherwise known as cat-scratch disease) or other animal exposures, environmental exposure such as swimming in fresh-water bodies or travel to certain regions.

Non-infectious causes

In the past, physicians assumed that if we couldn’t identify the cause of a case of encephalitis, the cause must be a virus that we weren’t able to detect. But now we recognize that encephalitis can also be caused by over-activity of your child’s immune system in a way that may not have been triggered by a virus.

It’s important to remember that the severity of symptoms has nothing to do with the cause, and two people might have equally severe cases of encephalitis caused by different factors.