Meningoencephalitis happens when you have inflammation and/or infection of your meninges and brain at the same time. It’s life-threatening, and early treatment is essential. Symptoms include fever, stiff neck and neurological issues, like light sensitivity, behavior changes and seizures. Treatment depends on the cause and severity.


What is meningoencephalitis?

Meningoencephalitis is a rare and life-threatening condition in which you have meningitis and encephalitis at the same time. Healthcare providers may also call it encephalomeningitis.

Meningitis is an infection or inflammation of the area surrounding your brain and spinal cord (meninges). Your meninges protect your brain and spinal cord from injury and provide support and structure. Encephalitis is inflammation in your brain tissue.

Both conditions usually develop due to an infection (like a viral or bacterial infection), but they can have other causes as well. Meningoencephalitis can affect anyone at any age, including infants.

Types of meningoencephalitis

There are different types of meningoencephalitis based on the underlying cause. But it’s most often related to an infection, like viral, bacterial, fungal and amoebic infections. Other potential causes include autoimmune diseases, like autoimmune encephalitis or meningoencephalitis, or medication-related side effects (such as from immune checkpoint inhibitor therapy).

Some common infections include:

  • Bacterial meningoencephalitis: This condition comes from a bacterial infection. Neisseria meningitides (meningococcal disease), Streptococcus pneumoniae and Haemophilus influenzae type b are the most common causes of bacterial meningoencephalitis.
  • Cryptococcal meningoencephalitis: This fungal infection happens when Cryptococcus fungi affect your brain and/or lungs.
  • Herpetic meningoencephalitis (HME): This condition can develop from an infection of the herpes virus. Most cases result from herpes simplex virus type 1 (HSV1) — the virus that causes cold sores. But it can also develop from herpes simplex virus type 2 (HSV2). Sometimes, meningoencephalitis happens during the initial infection. But it most often occurs due to the reactivation of the virus from an earlier infection.
  • Primary amebic meningoencephalitis (PAM): This condition comes from an amoeba called Naegleria fowleri. It lives throughout the world in warm and shallow bodies of fresh water, such as lakes, rivers and hot springs. It’s commonly called the “brain-eating amoeba.”


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Symptoms and Causes

What are the symptoms of meningoencephalitis?

Symptoms of meningoencephalitis include:

Other symptoms of meningoencephalitis that can affect infants include:

  • Bulging forehead.
  • Feeding issues.
  • Difficulty arousing or excessive sleepiness.

Symptoms of meningoencephalitis typically develop and progress quickly.

If you or your child have these symptoms, seek immediate medical help. Meningoencephalitis is life-threatening, and early treatment is essential.

What causes meningoencephalitis?

Infectious diseases, like viruses, bacteria, fungi and the amoeba Naegleria fowleri, are the main causes of meningoencephalitis.

These infections can spread through air, water, food or close contact with somebody else who has them. Not everyone who gets these infections develops meningoencephalitis.

In the rare cases of an autoimmune cause, the reason may not be entirely clear. Some risk factors include a personal or family history of autoimmunity, younger age and being assigned female at birth.

Is meningoencephalitis contagious?

Meningoencephalitis itself — inflammation in your brain and meninges — isn’t contagious. But some of the causes of it are. Most bacterial and viral causes of meningoencephalitis can spread from person to person, like the herpes simplex virus.

What are the risk factors for meningoencephalitis?

People with a weakened immune system (immunocompromised) are at increased risk of developing infectious meningoencephalitis.

Conditions and factors that weaken your immune system include:

If you’re immunocompromised, talk to your healthcare provider about ways to stay healthy and decrease your risk of serious infections.


Diagnosis and Tests

How is meningoencephalitis diagnosed?

If you or your child have signs of meningoencephalitis, a healthcare provider will act quickly to confirm a diagnosis. They’ll do physical and neurological exams. And they’ll ask questions about your symptoms, like when and how they developed.

Tests providers use to confirm a diagnosis of meningoencephalitis include:

  • Body fluid tests: Providers can test different body fluids like urine (pee), blood and saliva to look for signs of an infection (like white blood cell counts). These tests can also detect the specific type of infection.
  • Spinal tap (lumbar puncture): To perform a spinal tap, your provider inserts a needle into your lower back to get a cerebrospinal fluid (CSF) sample. A lab tests the fluid sample to check for the presence of bacteria, fungi or abnormal cells; protein types and levels; and white blood cell types and levels. Providers most often use CSF tests to distinguish meningoencephalitis from other conditions like blood toxicity or sepsis.
  • EEG (electroencephalogram): An EEG measures and records your brain’s electrical signals. Providers look for issues with how your brain is functioning to help diagnose or assess meningoencephalitis.
  • CT (computed tomography) scan: A CT scan is an imaging test that uses a series of X-rays (radiation) and a computer to create detailed images of inside your body. It can show issues in your brain or meninges, like clots, swelling, infection or inflammation.
  • MRI (magnetic resonance imaging): An MRI scan is an imaging test that uses a large magnet, radio waves and a computer to produce detailed images. Like a CT scan, it can show any issues with your brain or meninges. Healthcare providers prefer to use MRI for infants and children because it doesn’t use radiation, which can be harmful to children.

Management and Treatment

How is meningoencephalitis treated?

The treatment for meningoencephalitis depends on the cause and severity. Most cases require treatment in a hospital. Treatments may include:

  • Medication to treat the underlying infection: Cryptococcal meningoencephalitis, for example, requires antifungal medication. Providers use antiviral medications (like acyclovir) for herpetic meningoencephalitis.
  • Antiseizure medications: Providers use antiseizure medications, like dilantin or phenytoin, to prevent or treat seizures related to meningoencephalitis.
  • Corticosteroids and diuretics: Corticosteroids (like decadron) can help reduce swelling due to inflammation. They may also help prevent hearing loss related to meningoencephalitis.
  • CSF drainage: This can also help reduce intracranial pressure.
  • Pain relievers and/or sedatives: Providers may use these medications in cases of severe inflammation.

Your healthcare team will continue to closely monitor you as you stay in the hospital. They’ll address any issues or complications you may experience.



Can I prevent meningoencephalitis?

Not all cases of meningoencephalitis are preventable. But the best strategy for lowering your risk is to try to stay healthy and avoid bacteria, viruses and fungi that cause infections.

Strategies for protecting yourself and others against infections include:

  • Washing your hands frequently with soap and water.
  • Covering your mouth and nose when you cough or sneeze.
  • Disinfecting frequently touched surfaces.
  • Avoiding or minimizing contact with others when either of you are sick with a contagious disease.
  • Not swimming in or drinking water that could be contaminated. Use distilled or treated water for nasal irrigation.
  • Reducing your risk of sexually transmitted infections (STIs) by using condoms and regularly getting tested for STIs.
  • Reducing your risk of fungal infections by wearing a mask in dusty areas like construction sites and staying inside during dust storms. Take extra precautions if you live in areas where fungal infections are common.
  • Seeing a healthcare provider regularly, especially if you’re at increased risk of getting infections (like if you’re immunocompromised).
  • When traveling, learn how to reduce your risk of infectious diseases that are common in your destination.

Outlook / Prognosis

What is the prognosis for people with meningoencephalitis?

The prognosis (outlook) for people with meningoencephalitis depends on the cause, its severity and how quickly they receive treatment.

In survivors of cryptococcal meningoencephalitis, about 69% have cognitive and/or physical impairments 12 months after diagnosis. About 50% to 70% of people with herpetic meningoencephalitis experience permanent brain damage, neurological disorders or coma.

People who have mild cases and receive timely treatment are more likely to have fewer complications.

A note from Cleveland Clinic

Meningoencephalitis is a serious, life-threatening condition. If you or your child have symptoms, get medical help immediately. Early treatment is essential for a better outcome. If you’re at increased risk of getting infections that can lead to meningoencephalitis, talk to your healthcare provider about how to lower your risk and stay healthy.

Medically Reviewed

Last reviewed on 07/25/2023.

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