Granulomatous Meningoencephalitis (GME) in Dogs

What Is Granulomatous Meningoencephalitis (GME) in Dogs?

If your dog is experiencing a progressive disease affecting their brain, your veterinarian may mention an uncommon condition called granulomatous meningoencephalitis (GME). This condition affects the brain and spinal cord (central nervous system or CNS) in dogs.

The term meningoencephalitis refers to inflammation of the brain, spinal cord, and the membranes around the brain and spinal cord (meninges). GME refers to granulomatous inflammation, which describes the specific types of white blood cells involved (macrophages, lymphocytes, and plasma cells).

When a dog has GME, these white blood cells form cuffs around the brain’s blood vessels and the spinal cord, which form nodules when joined.

The three main types of GME include focal, disseminated or multifocal, and ocular.

Focal GME is limited to one area within the central nervous system and has a slower progression of three to six months. The disseminated form, which is the most common form, affects multiple areas of the CNS and has a rapid progression over two to six weeks. The ocular form only affects the eyes. A dog can have more than one type of GME.

Although dogs of any age or breed can develop GME, the disease is most common in middle-aged toy and terrier breeds. Dogs normally develop GME from age 4 to 8.

Symptoms of Granulomatous Meningoencephalitis in Dogs

Clinical signs depend on which part of the central nervous system is impacted. Common symptoms with the focal and disseminated forms include:

• Seizures

• Neck pain

• Wobbly gait

• Knuckling or dragging feet when walking

• Walking in circles

• Blindness

• Lack of engagement in surroundings

• Tilted head

• Facial abnormalities (such as paralysis in part of the face)

• Weakness

The ocular form typically presents with sudden blindness in one or both eyes without other neurologic signs.

Causes of Granulomatous Meningoencephalitis (GME) in Dogs

There is no known specific cause of granulomatous meningoencephalitis. However, the condition is most common in middle-aged, small-breed dogs. Predisposed breeds include:

• Chihuahuas

• Dachshunds

• Maltese

• Miniature Poodles

• Rat Terriers

• Toy Poodles

• West Highland White Terriers

• Yorkshire Terriers

While genetic predisposition likely plays a role in the development of GME, an excessive immune response (autoimmune condition) may be a contributing factor.

How Veterinarians Diagnose Granulomatous Meningoencephalitis (GME) in Dogs

Since many inflammatory conditions of the central nervous system are difficult to definitively diagnose, veterinarians often diagnose GME and other similar conditions as meningoencephalomyelitis of unknown origin (MUO).

The veterinarian will perform a neurological exam, which includes testing reflexes and watching your dog walk. This exam helps the veterinarian determine which part of the central nerve system may be affected.

A dog with neurologic signs will most likely have their blood drawn and a urinalysis to check overall body function and look for signs of infection, such as a high white blood cell count.

Additional testing can include:

• Magnetic resonance imaging (MRI), which allows the veterinarian to examine cross-sectional images of the brain and spinal cord.

• Cerebrospinal fluid (CSF) analysis, which involves collecting a sample of the fluid that surrounds the brain and spinal cord. This procedure requires anesthesia to keep the dog from moving or feeling pain.

• Infectious disease testing to rule out causes like distemper virus, fungal infections, or tick-borne infections that cause neurological signs.

GME can only be definitively diagnosed by examining brain tissue under a microscope, which is normally done as part of a necropsy.

Treatment of Granulomatous Meningoencephalitis (GME) in Dogs

GME is believed to have an autoimmune component, so suppressing the immune system is the primary goal of treatment. GME cannot be cured, so treatment aims to manage the symptoms and preserve quality of life.

Most dogs start on steroids, often prednisolone, to reduce inflammation and suppress their immune system. In the long term, other immunosuppressive drugs like cytosine arabinoside (a chemotherapy agent) or cyclosporine (an immunomodulator) may be added to the treatment protocol.

Dogs with ocular GME will usually also be given oral steroids, but some veterinarians may recommend steroids applied directly in the eye. If the dog develops glaucoma (high pressure within their eye), this condition also need to be managed. Medications for glaucoma, such as dorzolamide and timolol, are aimed at decreasing fluid production and promoting fluid drainage from the eye.

Radiation therapy may be an option for focal lesions. Dogs undergoing radiation must be anesthetized. Importantly, radiation to the head can result in other issues, such as seizures or cataracts. Options for controlling seizures due to GME include standard seizure medications.

Treatment cannot be stopped, or signs will recur. The goal of treatment is to find the lowest dose required to control disease. Despite this, relapses are common.

Recovery and Management of Granulomatous Meningoencephalitis (GME) in Dogs

Granulomatous meningoencephalitis is not curable and lifelong management is required. While it’s possible to keep your dog comfortable for some time and improve quality of life, most dogs with focal or disseminated GME who show worsening clinical signs will eventually be euthanized.

Younger dogs may have increased survival times, but dogs that have seizures or mental activity changes typically have shorter ones. Early diagnosis and treatment within the first seven days of clinical signs may also improve survival time. While around 15% to 25% of dogs with GME die of the disease or are euthanized within the first week of diagnosis, dogs that survive the first month have a decent chance of living for months, possibly more than a year.

While ocular GME typically causes sudden, permanent blindness, it’s not life-threatening unless other forms of GME exist concurrently.

Your dog’s coordination is likely to be affected, so placing nonslip mats on hard floors can help your dog get around. Consider using ramps or small steps onto furniture so your dog doesn’t have to jump. Keep food and water bowls easily accessible. If your dog is having seizures, consider placing a bell on their collar, which may alert you if he is having a seizure in another room.