An Overview of Meningoencephalitis

A Serious Inflammation of the Brain and Meninges

Meningoencephalitis has similarities with 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 often used to denote both conditions."

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

When both the meninges and the brain are inflamed, it’s considered meningoencephalitis. It can also be referred to as encephalomeningitis.

Meningoencephalitis can have different causes, and herpes virus infection is the most common cause.

meningoencephalitis is often viral and may be treated with acyclovir
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Types of Meningoencephalitis

There are several types of meningoencephalitis, classified according to the underlying cause. Several organisms (germs) can cause this condition.

Types of meningoencephalitis include:

  • 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, it tends to affect people who have a suppressed immune system due to medication, cancer, or HIV.
  • Bacterial meningoencephalitis: Sometimes referred to as pyogenic meningoencephalitis, it is a very serious life-threatening infection with a high risk of mortality (death) and complications, such as disability.
  • Parasitic meningoencephalitis: This is caused by a reaction to a parasite, usually transmitted by eating contaminated food.
  • Secondary meningoencephalitis: This type occurs when an infection starts somewhere else in the body, then travels to the brain.
  • HIV meningoencephalitis: The human immunodeficiency virus (HIV) can infect the brain and meninges within weeks or months of HIV diagnosis.
  • Aseptic meningoencephalitis: This describes viral and non-infectious causes, and it is usually diagnosed when the cerebrospinal fluid (CSF) that surrounds the brain and spinal column tests negative for bacteria.
  • Primary amebic meningoencephalitis: This rare form of meningoencephalitis that is usually fatal, involves an infection caused by the amoeba Naegleria fowleri. It’s usually contracted by swimming in contaminated water, and also has occurred from 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

In a small study conducted in 2012 in Bangladesh that involved 140 hospitalized children, a pyogenic (pus-forming) form of meningoencephalitis was found in 18.5% of those with meningoencephalitis, a viral form 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) can be early signs of meningitis. Severe symptoms such as a focal neural deficit, continual sleepiness, and seizures, may indicate 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
  • Headaches
  • Speech problems
  • Purple rashes (indicative of viral meningoencephalitis)
  • Disorientation

 Later symptoms in children may include:

  • Vomiting
  • Drowsiness
  • Seizures
  • Behavioral changes
  • Unconsciousness

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

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

Causes of Meningoencephalitis

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 or Aseptic Causes

Viral meningoencephalitis is primarily caused by herpes simplex viruses, including herpes simplex type 1 and herpes virus type 2.

There are two types of herpes simplex virus:

  • 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. They can be dormant, not causing any signs or symptoms of infection, and then can reactivate. Sometimes meningoencephalitis is contracted during the initial herpes infection, but it usually occurs during reactivation of the virus from a previous infection.

Other causes of viral or aseptic meningoencephalitis may include:

Bacterial Causes

There are several organisms that can cause bacterial meningoencephalitis. Most bacterial sources of meningoencephalitis are spread from person to person, and they are spread differently, depending on the type.

The most common causes of bacterial 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. 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

Diagnosis

A physical and neurological examination is performed to evaluate for 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 needle aspiration of a sample of cerebrospinal fluid (CSF), to check for inflammatory cells, proteins, and organisms.
  • CSF culture: The CSF sample is examined microscopically for bacteria, fungi, and red and white blood cells. A sample is incubated in culture media to identify whether there's growth of causative bacteria such as N. meningitidis, S. pneumoniae, and H. influenzae.
  • Electroencephalogram (EEG): The test is performed by placing electrodes on the scalp that provide a reading on a person’s brain wave activity to identify certain brain function disturbances.

Imaging

Brain 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. An injected dye may help delineate the images.
  • Magnetic resonance imaging (MRI) scan: This imaging test uses radio waves and very strong magnetic fields to create a series of detailed images of the brain.
  • Ultrasound or sonography: This test uses sound waves to make an image of the structure and fluid flow in the brain. Brain changes such as swelling, lesions, or inflammation can sometimes be detected using ultrasound technology.

Treatment

The main goals of treating meningoencephalitis are to treat the symptoms and the cause of inflammation. 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 the administration of an intravenous antiviral medication such as acyclovir, for up to 14 days.

Other antiviral medications may include vidarabine or famciclovir. During the later stage of the infection, these antiviral medications are less effective.

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

Medications

Other medications that may be given for managing all types of meningoencephalitis 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).
  • Pain medications or sedatives

Miscellaneous Treatment

Supervision, bed rest, and other measures are important to prevent worsening symptoms.

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

With mild meningoencephalitis, recovery usually occurs 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 take effect in a day or two and full recovery can take about four weeks. Without treatment, serious complications—including death—often occur.

In 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
  • 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 techniques, meningoencephalitis continues to be a serious infectious disease with a high rate of fatality (death).

Prevention

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

Several important preventative measures can 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 not 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 reduce the risk of newborn meningoencephalitis, talk to your obstetrician about the risks and benefits of having a cesarean section if you've had genital herpes outbreaks.

A Word From Verywell

Meningoencephalitis is 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, sensitivity to light, or fever with a bad headache) that are otherwise unexplained, it’s important that you seek medical attention as soon as possible. 

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