Granuloma Meninegoencephalitis in Dogs

Granulomatous Meningoencephalitis (GME), also known as Inflammatory Reticulosis, is an acute inflammatory disease of a dog’s central nervous system. This progressive disease can cause significant and in many cases, irreversible damage to the central nervous system. The disease occurs worldwide and dogs of most ages and breeds can be impacted, though those most likely to be affected are small breed dogs in middle age (for example Terriers and Poodles). Up to 25% of all disorders of the central nervous system in dogs in the United States are due to GME. The cause of GME is not clear; in fact, there may be several ways to develop the condition.

Granulomatous Meningoencephalitis is an acute inflammatory disease that impacts a dog’s central nervous system, often causing irreversible damage and progressing to death without treatment.

The symptoms that your dog experiences will depend on where there are lesions in his body. Common symptoms include:

• Neck pain
• Rigid stance
• Not wanting to move
• Muscle spasms along his spine
• Lost function in limbs
• Fever
• Vision loss

Symptoms are typically acute, though in the focal form you may notice neurologic deficits that slowly progress over several months.

Types 

There are three types of GME:

Ocular form

In this form, which is uncommon, your dog will have a sudden loss of vision in his eyes. Multiple parts of the eye can be affected and in this form of the disease there may be no other symptoms for months until the disease has spread to the central nervous system.

Focal form

The symptoms in this form make it appear that the disease is only affecting one or two parts of your dog’s brain. Upon examination however, lesions will be located throughout the brain. This form used to be called neoplastic reticulosis and involves granulomatous lesions that are made up of mainly reticulohistiocytic cells. Chronic and progressive, this form may partially respond to medications for a period of time.

Disseminated form

This form progresses the most rapidly and lesions will be present throughout your dog’s nervous system. The symptoms that your dog displays will depend on where his lesions are located; the most common sites affected are the lower brainstem, cervical spinal cord and meninges.

The cause of GME is not known though it is suspected that the disease is caused by an infectious agent, most likely a virus. In some dogs with GME, cancer cells are associated with the lesions, although this is not always the case. It is thought that in some cases GME will result from a fungal infection. Dogs of any breed may be affected by GME;  it is more likely in young to middle aged female, small-breed dogs, particularly Poodles.

Should you notice that something seems wrong with your dog, it is important to take him to the veterinarian. Your veterinarian will conduct a physical examination of your dog and ask you for additional information regarding his symptoms, when you first noticed them and whether they have gotten worse. The clinical signs that your dog is experiencing will be considered; signs are often variable and may point to one or more areas of dysfunction in your dog’s brain or spinal cord. For example, cervical pain and weakness that impacts all four of your dog’s extremities are the most common signs indicating spinal cord involvement.

Your dog will likely undergo an MRI and CT scan which in many cases will show one or more than one mass. A tentative diagnosis can be made by your veterinarian through an examination of your dog’s cerebral spinal fluid through a CSF tap, clinical findings, imaging and excluding other possible diseases. Confirmation of the diagnosis can only be made through a brain biopsy or examining your dog’s brain tissue after he has died.

Should your dog be suffering from GME, immunosuppressive doses of corticosteroids may be recommended by your veterinarian. Improvement is often seen with corticosteroids and other immunomodulating drugs such as:

• Cytarabine
• Cyclosporine
• Procarbazine

Treatment may involve radiation therapy or a combination of both immunosuppressive drugs and radiation therapy. Your dog may show improvement and even go into remission, however, relapse may occur. Many dogs with GME eventually become resistant to treatment. Without treatment, the disease will typically progress to death within a few months.

Should your dog be diagnosed with GME, follow up appointments will be required. Your veterinarian may try immunosuppressive drugs without radiation and depending upon the results may recommend radiation therapy as well. To ensure the best prognosis for your dog it is important to follow the recommendations of your veterinarian and attend all follow up appointments.