Irritation and swelling, called inflammation, of the brain and the tissues around it, most often caused by infection.

Meningoencephalitis is a condition most often caused by a virus, bacteria or fungal infection. Examples include measles, mumps or pneumonia.

Symptoms depend on the cause. They may include fever, confusion, vomiting, seizures, stiff neck and headache. Untreated, meningoencephalitis can be fatal.

Treatment may include antibiotics, antivirals and supportive care. Treatment depends on the cause of the disease.