An Overview of Meningoencephalitis

A Serious Inflammation of the Brain and Meninges

Meningoencephalitis has similar symptoms and a similar course of disease as both encephalitis and meningitis. According to a 2012 study, "It is often difficult to reliably differentiate meningitis and encephalitis clinically. Therefore, the term acute meningoencephalitis (AME) is used to denote both conditions."

Meningitis is a condition that involves inflammation, due to infection of the meninges (the protective layer of membranes that surround the brain). Encephalitis is an inflammation/infection of the brain itself. Encephalitis could occur on its own, or it can happen simultaneously with meningitis.

 When both the membranes of the brain (meninges) and the brain itself are inflamed, it’s called meningoencephalitis. It can also be referred to as encephalomeningitis.

There are several types of meningoencephalitis, classified according to the underlying cause. Meningoencephalitis can have different causes, but most commonly a diagnosis of meningoencephalitis involves the type that comes from the herpes virus.

meningoencephalitis is often viral and may be treated with acyclovir
Shidlovski / Getty Images

Types of Meningoencephalitis

There are several types of meningoencephalitis including:

  • Herpes meningoencephalitis (HME): This is the most common form of meningoencephalitis, caused by the herpes virus.
  • Fungal meningoencephalitis: Resulting from the spread of the fungus through the bloodstream, those with a suppressed immune system such as people with cancer or HIV are at an increased risk of this type of meningoencephalitis.
  • Bacterial meningoencephalitis: Sometimes referred to as pyogenic meningoencephalitis, it is a very serious life-threatening infection with an increase in the rate of mortality (death) and complications such as disability.
  • Parasitic meningoencephalitis: This is caused by a reaction to a parasite, usually transmitted by eating the flesh of infected animals or contaminated foods.
  • Secondary meningoencephalitis: This type occurs when an infection starts somewhere else in the body, then travels to the brain.
  • HIV meningoencephalitis: An infection in the brain and meninges by the human immunodeficiency virus (HIV) occurs secondary to HIV infection. It can happen within weeks or months of a diagnosis of HIV.
  • Aseptic meningoencephalitis: This occurs in those who test negative for bacteria in the fluid that surrounds the brain and spinal column, called cerebrospinal fluid (CSF).
  • Primary amebic meningoencephalitis: A very rare form of meningoencephalitis that is usually fatal, it involves an infection caused by the amoeba Naegleria fowleri. It’s usually contracted by swimming in a contaminated water source, but also has been seen in using contaminated water in a neti pot.
  • Japanese encephalitis (JE): This is the primary type of meningoencephalitis in Asia, caused by the Japanese encephalitis virus. It is preventable by vaccine.

Study

A small study, conducted in 2012 in Bangladesh, discovered that of 140 hospitalized children, a pyogenic (pus-forming) form of meningoencephalitis occurred in 18.5% of those with meningoencephalitis, a viral form was present in 10% of the cases and bacterial causes were identified in 8.5% of the children in the study.

Meningoencephalitis Symptoms

Meningoencephalitis causes a range of symptoms, depending on the severity of the condition, common symptoms include:

  • Fever
  • Light sensitivity
  • Headache
  • A stiff neck
  • Confusion
  • Difficulty thinking clearly
  • Hallucinations (seeing or hearing things that aren’t actually there)
  • Unusual behaviors
  • Personality changes
  • Fatigue or sleepiness
  • Seizures
  • Focal neural deficit (a problem with nerve function in a specific area of the body)
  • Unconsciousness

Mild symptoms (such as fever and headache) could indicate a case of meningitis. Severe symptoms such as a focal neural deficit, continual sleepiness and seizures, may likely indicate that the brain, as well as the meninges are infected and that a person has meningoencephalitis.

Symptoms in Children and Infants

Just as in adults, the symptoms of meningoencephalitis in children and newborns usually begin like symptoms of the common flu. Early symptoms in children may include:

  • Fever
  • Speech problems
  • Disorientation

 Later symptoms in children may include:

  • Headache
  • Vomiting
  • Fever
  • Drowsiness
  • Seizures
  • Unconsciousness
  • Behavioral changes
  • Purple rashes (indicative of viral meningoencephalitis)

In infants, the primary symptoms of herpes type 2 which occur from transmission at birth usually include:

  • High fever
  • Bulging of the forehead
  • Poor appetite/feeding
  • Continual sleepiness

Causes of Meningoencephalitis

There are a variety of causes of the condition.

Viral or Aseptic Causes

Although meningitis is primarily caused by bacteria, viruses can be the culprit in the cause of both encephalitis and meningitis (with an equal rate of occurrence).

Meningoencephalitis can be caused by various types of organisms (including viruses, bacteria, and protozoa) or it can occur as a secondary development caused by other types of inflammation (such as HIV).

Viral meningoencephalitis is primarily caused by herpes viruses (including herpes simplex type 1 and herpes virus type 2). Other causes of viral or aseptic meningoencephalitis may include:

The organism (germ) that causes meningoencephalitis depends on the type of the disease. Most commonly the underlying cause is the herpes simplex virus, indicating that a person has viral meningoencephalitis. There are two types of herpes viruses, including:

  • Herpes simplex virus type 1 (HSV1): The virus that causes cold sores and the most common type of herpes that causes meningoencephalitis. HSV1 is also known to be sexually transmitted to the genital area.
  • Herpes virus type 2 (HSV2): Can be spread through sexual contact or from a mother who is infected with HSV2 to her unborn child during birth. 

The herpes viruses stay in the body for a person’s entire life; it can be dormant, not causing any signs or symptoms of infection, and then it can reactivate. Sometimes meningoencephalitis is contracted during the initial herpes infection, but usually it occurs during reactivation of the virus from a previous infection.

Bacterial Causes

There are several organisms that can cause bacterial meningoencephalitis. The germs are spread differently, depending on the type. Most bacterial sources of meningoencephalitis are spread from person to person. The most common three types of bacteria that cause meningoencephalitis include:

  • Streptococcus pneumoniae: A bacteria commonly found in the nose and throat
  • Haemophilus influenzae (HIB): A type of bacteria that commonly causes respiratory infections, and which is preventable by vaccine.
  • Neisseria meningitidis: A type of bacteria that commonly lives in the back of the nose and mouth without causing any adverse symptoms, a severe infection is preventable by vaccine

Transmission

Common modes of transmission (spread of the disease) for the bacteria that can cause meningoencephalitis include:

  • Coughing or sneezing (HIB and S. pneumoniae)
  • Kissing or close contact in which saliva is shared (N. meningitidis)

Viral meningoencephalitis caused by the herpes simplex type 1 and the herpes virus type 2 is often transmitted by:

  • Droplet spread (such as from coughing or sneezing)
  • Water or food transmission
  • Sexual intercourse
  • Oral to oral contact (via sores and saliva as well as other surfaces in or around the mouth)
  • Transmission from mother to child during childbirth

Study

The 2012 Bangladesh study discovered that the primary cause of acute bacterial meningoencephalitis in the children who were hospitalized was S. pneumoniae.

Diagnosis

A physical and neurological examination is performed to evaluate for the presence of abnormalities in motor and sensory function, coordination, balance, and altered mental status. If the healthcare provider suspects meningoencephalitis, some lab tests will be performed, including:

  • Blood tests: These will evaluate the presence of an infection in the body.
  • Lumbar puncture: This procedure involves a needle aspiration of some cerebrospinal fluid (CSF), to check for substances and organisms.
  • CSF culture: After obtaining a sample via lumbar punction, the CSF is examined microscopically for bacteria, fungi, and red and white blood cells. A sample is incubated in culture media to look for an identify causative bacteria such as N. meningitidis, S. pneumoniae, and H. influenzae.
  • Electroencephalogram (EEG): To measure the brain waves, the test is performed by placing electrodes on the scalp that provides a reading on a person’s brain wave activity.

Imaging

Imaging that may be used includes:

  • Computerized tomography (CT) scan: This is an imaging test that takes many different pictures from various angles inside of the body. A dye may be given to swallow before that test to enable the brain to show up more clearly in the images.
  • Magnetic resonance imaging (MRI) scan: This imaging test uses radio waves and very strong magnetic fields to make a series of detailed images of the brain.
  • Ultrasound or sonography: This test uses sound waves to make an image of the structure and secretions from the brain. Brain changes such as swelling, lesions, or inflammation can be detected using ultrasound technology.

Treatment

The main goals of treating meningoencephalitis are to treat the underlying cause of the infection and to begin treatment as soon as possible. The treatment modality differs according to the type of meningoencephalitis you have.

In the most common form of the disease, herpes meningoencephalitis (HME), the treatment involves administration of an antiviral medication such as acyclovir. Usually the acyclovir is given via IV (intravenous) administration for up to 14 days.

Other antiviral medications may include vidarabine or famciclovir. Note, during the later stage of the infection, these antiviral medications are ineffective.

For bacterial causes of meningoencephalitis, IV antibiotics are given. The type of antibiotic depends on the causative germ/organism.

Medications

Other medications which may be given for all types of meningoencephalitis may include:

  • Medication to prevent seizures (such as dilantin or phenytoin)
  • Medications aimed at lowering the pressure and swelling in the brain (such as corticosteroids and diuretics, like prednisone, furosemide or mannitol).
  • Pain medications or sedatives

Miscellaneous Treatment

Depending on how severe the case of meningoencephalitis is, hospitalization may be ordered. Supervision, bed rest, and other measures are important to prevent recurrence of the infection.

Miscellaneous types of treatment depend on the severity of the condition. Rehabilitation, rest, balanced nutrition and modalities such as occupational therapy may be required.

Prognosis

In people with mild meningoencephalitis, recovery will usually occur within a few weeks of starting treatment; but in severe cases, nearly 50 to 70% of people will develop secondary brain damage, neurological (nerve) disorders or coma. This is the reason that prompt intervention is so important.

Prompt treatment usually begins to be effective in a day or two and people usually recover fully within four weeks. But without treatment, serious complications—including death—often occur.

n severe cases of meningoencephalitis, serious complications can occur even with proper treatment. These include:

  • Problems with memory
  • Speech/language problems
  • Changes in personality or behavior
  • Problems swallowing
  • Seizures
  • Emotional problems (such as anxiety or depression)
  • Trouble with thinking skills (such as concentration, attention, and problem solving)
  • Physical problems with balance and coordination
  • Long term fatigue

Despite the recent advancements in medical treatment and early detection technique, meningoencephalitis continues to be a serious infectious disease with a high rate of fatality (death).

Prevention

The recommended childhood vaccines will prevent several types of meningoencephalitis. These include measles mumps and rubella (MMR) vaccine, chickenpox vaccine, pneumococcal vaccine, and Hib vaccine. Meningococcal vaccine is also available to protect adolescents.

There are several important prevention measures that can be put in place to help lower your risk of getting herpes meningoencephalitis, these include:

  • Avoid having sex with partners who may be exposed to the herpes virus
  • To reduce the risk of infection, use a latex condom or dental dam during sexual contact. Condoms do always prevent herpes transmission, but they can lower the risk of getting the virus.
  • Don’t kiss a person with a cold sore blister, which is a symptom of active oral HSV infection.
  • To prevent the possibility of meningoencephalitis in newborns, discuss with your obstetrician or other healthcare provider the possibility of having a cesarean section if you have had genital herpes outbreaks.

A Word From Verywell

Meningoencephalitis is considered a medical emergency. It’s vital to get treatment for meningoencephalitis as soon as possible. If you have symptoms (such as neck stiffness, seizures, changes in consciousness or sleepiness, sensitivity to light or fever with a bad headache) that are otherwise unexplained, it’s important to seek medical consultation with a healthcare provider as soon as possible. 

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rasul CH, Muhammad F, Hossain MJ, Ahmed KU, Rahman M. Acute meningoencephalitis in hospitalised children in southern BangladeshMalays J Med Sci. 2012;19(2):67-73.

  2. Johns Hopkins Medicine. What is herpes meningoencephalitis?

  3. Bolz B, Di Muzio B. Pyogenic meningitis. Radiopaedia.

  4. Centers for Disease Control and Prevention. Parasitic meningitis. Updated August 6, 2019.

  5. Dash SK. Herpes meningoencephalitis: Causes, diagnosis, and treatment. in: Meningoencephalitis - disease which requires optimal approach in emergency manner. 2017. doi:10.5772/intechopen.68553

  6. The World Health Organization. Herpes simplex virus. Updated May 1, 2020.

  7. The Centers for Disease Control and Prevention (CDC). Primary culture and presumptive identification of Neisseria meningitidis,Streptococcus pneumoniae, and Haemophilus influenzae.

  8. National Health Service. Complications: Encephalitis. Updated December 3, 2019.