Your Guide to Granulomatous Meningoencephalitis in Dogs

Granulomatous Meningoencephalitis (GME) is an inflammatory disease of the central nervous system. Occurring most commonly in young to middle-aged small breed dogs, including pugs, various terrier breeds, Maltese, Chihuahuas, and poodles, GME can cause unique symptoms depending on the form of GME and the brain region that’s affected.

Since GME can cause nearly any neurological symptom, including everything from seizures to blindness, it can be challenging to diagnose without fairly extensive testing; and once a diagnosis is made, treatment can be incredibly costly.

Although the prognosis is typically poor, in some cases, dogs can recover. However, this requires swift treatment; which is why it’s critical that dog owners understand the associated symptoms and possible complications.

Types of Granulomatous Meningoencephalitis and Associated Symptoms

Three core types of granulomatous meningoencephalitis exist, including:

Disseminated – The most common form, disseminated GME, tends to manifest suddenly and progress rapidly. Being a multifocal neurological disease, clinical signs indicate lesions in numerous brain regions.
Focal – Characterized by single-region lesions, focal GME often impacts the brainstem and cerebrum. Onset is generally slower, yet chronic and progressive in nature.
Ocular – Being the most uncommon form, ocular GME is generally characterized by sudden onset of blindness. Dogs with this form generally display evidence of optic neuritis — an inflammatory disease that targets the optic nerve.

Depending on the neurological region impacted, clinical signs will vary. In the forebrain, for example, dog owners may notice abnormal movements such as wandering and circling; behavioral changes, including increased aggression or hyper-excitability; seizures; tremors, etc. In comparison, when the midbrain is affected, mental depression may result, as well as hyperventilation, postural deficits, etc.

When dogs suffer from the disseminated form of GME, they may display dysfunction in two or more brain regions, including the cerebellum, brainstem, cerebrum, optic nerves, meninges, or spinal cord. This form accounts for approximately 50% of all cases.

GME, specifically, can be difficult to distinguish from other forms of meningoencephalitis (which is essentially inflammation of the brain). However, researchers believe that GME may represent up to 25% of all canine central nervous system disease.

GME Prognosis

When it comes to GME, time is of the essence. Being an acute and highly progressive disease, most dogs affected do not live long, particularly those who do not receive aggressive treatment.

The average survival period for all dogs with GME is approximately 14 days and those with multifocal signs typically live an average of 8 days. However, those showcasing signs in the forebrain live an average of more than 359 days. Upon receiving radiation therapy, on average, dogs with focal signs can survive more than 404 days.

Cause of GME and Breeds Most Commonly Affected

Based on patient data and the associated research, certain breeds are more susceptible to GME than others. Classically, GME develops in small breed dogs. However, any breed can get GME, including Great Danes, Pointers, German shepherds, etc.

Age is also a factor, as GME typically presents itself in young to middle-aged dogs. While there is a high degree of variability, affecting dogs between 5 months and 12 years, the average age of onset is approximately 5 years. In terms of sex, GME occurs in both sexes but tends to be more common in females.

At this time, there is no specific causation in terms of breed predisposition. Being an idiopathic inflammatory disease, the cause of GME is still unknown. Some researchers believe it is caused by viral infections while others believe that GME is simply a variant of CNS neoplastic reticulosis, which is associated with the abnormal growth of cells.

The most recent research suggests that GME is an immune-mediated disease that initiates an inappropriate response, likely impacting brain blood vessel circulation, initiating an immune response that increases inflammation.

How Is a Diagnoses Made and Can GME Be Treated?

The truth is, the majority of pet owners have never heard of GME. That is until their dog develops this brain disease and either rapidly or gradually worsens.

When a dog showcases brain-related symptoms, their general health history will be reviewed before performing blood work, a physical examination, and urinalysis. This can help determine what other systems may be involved.

In order to better understand a more specific cause, a spinal tap or MRI will be required. An MRI will help you identify whether or not visible lesions are present. A spinal tap will allow a veterinarian to evaluate cells in the cerebrospinal fluid. In this case, cancer cells, infectious organisms, or inflammatory cells may be found. Although inflammatory cells can represent a range of potential causes, these cells are typical of GME.

Unfortunately, the only way to truly confirm GME 100% is by biopsy. An MRI and/or spinal tap can be incredibly telling. However, confirmation is most frequently post-mortem.

Treatment Options Are Available But Costly

Medications and surgical treatment options are currently available and are recommended on a case-to-case basis. Currently, the most common therapy for GME is immune-suppression, using corticosteroids. However, a number of medications are available and will be prescribed based on each dog’s unique circumstances.

Studies have shown that outcomes are highly variable. However, immunosuppressive treatment is known to improve prognosis in comparison to no treatment. Treated dogs showcase median survival ranging from 1-3 years.

If the GME is focal, radiotherapy can be helpful. Although there are risks involved, many cases of focal GME result in complete resolution. This option is particularly successful when combined with corticosteroids, such as prednisolone.

The cost of this treatment is typically categorized into three phases — pre-diagnosis, diagnosis, and treatment. Each of these stages can cost hundreds if not thousands of dollars, with the treatment phase being the most expensive. Depending on the severity of a dog’s condition, radiotherapy can cost $5000+ alone.

Cost to Treat: $6,000 to $7,000

The treatment of GME can be incredibly costly, quickly adding up to thousands of dollars. To avoid making incredibly tough decisions, it’s important to take a proactive approach and protect your dog.

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