What Is MUE?

What Are MUE, MUO, GME, NME, NLE, and SRMA?

In simple terms meningoencephalitis of unknown etiology (MUE) is a category of fast progressive disease where the body's own immune system mistakenly attacks the brain, spinal cord, and their coverings (meningies).

Types of MUE: 

  • Granulomatous meningoencephalitis (GME)
  • Necrotizing meningoencephalitis (NME)
  • Necrotizing leukocencephalitis (NLE)
  • Steroid-responsive meningitis-arteritis (SRMA)

Regardless of the type of MUE, the inflammation in the brain can result in a range of neurological symptoms depending on the location of the inflammation and the severity of the disease.

Who Can Get MUE?

While any dog or cat of any breed or any age can be diagnosed with MUE, this is the most common profile: 
  • Small dog breeds (toy, terrier, poodles)
  • Young - middle aged dogs (average of 5 years)
  • Females

While these diseases are said to be idiopathic, meaning there is no known cause, recent studies on similar diseases may provide some important clues.

In the case of necrotizing meningoencephalitis (NME), a genetic marker has been identified which may make dogs with changes (mutations) in their DNA at higher risk for being diagnosed with NME.

Dogs or cats with this genetic mutation may be exposed to environmental triggers like vaccination, infections, or chronic inflammation which result in the onset of developing disease.

Once triggered, the immune system mistakenly attacks the body's own nervous system tissue much like what happens in human multiple sclerosis and other diseases that affects both humans, dogs, and cats.

While there is no cure for MUE, there are treatment options that, if caught early and treated aggressively, may extend your dog or cat's life.

We look forward to the day where future therapeutic options will be available keep this devastating disease in remission while minimizing the side effects from treatment.

More Information on the Types of MUE

Meningoencephalitis of Unknown Origin (MUO): Another term for MUE.

Granulomatous Meningoencephalomyelitis (GME)

Granulomatous meningoencephalomyelitis, or GME is a type of MUE where there are formations of small clumps of immune cells called granulomas. The granuloma clumps cause inflammation and damage to the nervous system tissue.

GME can appear in three different forms: ocular (least common), focal, and multifocal/disseminated (most common form). Learn about the 3 types of GME.

Pain, seizures, paralysis, and cerebellovestibular dysfunction are seen most commonly.

Necrotizing Meningoencephalitis (NME)
NME has also been described as “pug dog encephalitis,” but can affect Maltese, Pekingese, Chihuahua, and other toy breed dogs. NME has also been described in medium to large breed dogs, but much less commonly. As the name suggests, the inflammation leads to death of the brain tissue. Symptoms affect the cerebrum only and seizures are a very common clinical sign. Neck pain is also very common. Prognosis for NME is unfortunately not as good as some of the other MUE diseases.

Necrotizing Leukocencephalitis (NLE)
NLE is very similar to NME, except for the signalment and lesion location. Yorkshire terriers and French bulldogs tend to be predisposed to development of NLE. NLE affects both the cerebrum and brainstem. Patients typically show evidence of multifocal brain symptoms.

Steroid-Responsive Meningitis-Arteritis (SRMA)
SRMA is typically seen in young (less than two years old) medium to large breed dogs. Boxers, beagles, and Bernese Mountain dogs are predisposed.

It shares some clinical features with GME, such as neck pain, fever, and neurological signs.

The most common clinical signs are severe neck pain and fever. Concurrent nonerosive immune-mediated polyarthritis (IMPA) has also been commonly reported with SRMA patients.


MUE is Scary ~ Don't Lose Hope!

When Piper was diagnosed at the age of 9, her prognosis was very grim as she had advanced GME (inflammation) in every area of her brain.

Once Piper was diagnosed, we followed a strict and aggressive treatment plan, removed synthetic products from her environment, changed her food, supplements, treats, and more.

In short, we did everything we could think of to give her the best chance at remission. Read more about Piper's GME experience.

Piper lived to the age of 15.  Six years in GME remission.

There are 3 Types of GME

  • The most commonly diagnosed.
  • GME is in multiple areas of the nervous system. 
  • A rapid progression of disease, generally 2-6 months. 
  • There are often more symptoms with this type of GME as multiple areas of the brain are involved.
  • Without treatment, survival is, on average, 8-30 days.
  • With treatment, 44-75% of dogs respond well to treatment. Treatment speed and the aggressiveness of treatment is critical to survival.
It is possible to have both disseminated (or multifocal) and ocular at the same time.

Dr Karen Becker's Overview on GME

Learn More About the Meninges

The meninges in a dog's brain are the three protective layers of connective tissue that surround and encase the brain, providing support and protection. The three layers of meninges, from outermost to innermost, are:

  1. Dura mater: This is the outermost and toughest layer of the meninges. It is a thick, durable, fibrous membrane that surrounds the brain and spinal cord, providing structural support and protection.

  2. Arachnoid mater: This is the middle layer of the meninges, located between the dura mater and the pia mater. It is a delicate, web-like membrane that contains cerebrospinal fluid (CSF) in its subarachnoid space, which serves as a cushion for the brain.

  3. Pia mater: This is the innermost layer of the meninges, located closest to the surface of the brain. It is a thin, delicate membrane that directly covers the brain, following its contours closely.

These three layers of meninges work together to protect the delicate brain tissue from injury, provide support, and help maintain the appropriate environment for proper brain function in dogs, as well as in other animals with similar neuroanatomy.

Learn More About Granulomas

Granulomas are small, organized nodules or clusters of immune cells that can form in response to various inflammatory conditions.

They are typically composed of macrophages, which are a type of white blood cell, along with other immune cells such as lymphocytes.

Granulomas are formed as part of the body's defense mechanism against foreign substances or infectious agents that the immune system is unable to fully eliminate.

Granulomas can occur in various organs and tissues throughout the body, including the lungs, skin, liver, spleen, lymph nodes, and gastrointestinal tract. They are often seen in conditions such as tuberculosis, sarcoidosis, Crohn's disease, and some fungal or parasitic infections. Granulomas can also be caused by exposure to certain substances, such as foreign bodies, certain drugs, or environmental toxins.

In the case of GME, they can cause inflammation, damage to surrounding tissues, and symptoms depending on their location and underlying cause.