Granulomatous Meningoencephalomyelitis (GME) in Dogs

Overview of Canine Granulomatous Meningoencephalomyelitis (GME)

Granulomatous meningoencephalomyelitis (GME) is a sporadic inflammatory disease of the central nervous system (CNS) in dogs characterized by large perivascular accumulations of mononuclear cells in the parenchyma and meninges of the brain and spinal cord. It rarely occurs in cats. Previously, GME has been described as inflammatory reticulosis, granulomatous reticulosis, hestiocytic encephalitis, and neoplastic reticulosis.

The cause of GME is unknown or idiopathic. Infectious, immune, and neoplastic causes have been proposed on the basis of findings from small series of cases. However, a single cause of GME has not been demonstrated. GME may also represent early cancerous (neoplastic) transformation. However, all theories related to the cause of GME remain unproven.

It is most common in middle age dogs, although it can occur from age six months to ten years. Female dogs are slightly more affected than male dogs, and small breed and specifically poodles appear to be more commonly affected.

The location of GME may occur either in the meninges (menigo), brain (encephalo), or the spinal cord (myelitis). It may affect one, two, or all three components of the CNS.

What to Watch For

Clinical signs are variable and reflect the area of the CNS affected. If GME affects the forebrain, clinical signs could involve:

• Blindness
• Seizures
• Altered mental status
• Pacing
• Circling
• Head pressing
• Stumbling with a nearly normal gait

If GME affects the hindbrain (brainstem +/- cerebellum), clinical signs may include:

• Falling
• Rolling
• Inability to blink
• Facial paralysis
• Voice change
• Mental depression
• Tremors
• Spastic gait and broad based stance

Spinal cord involvement of GME may include such signs as:

• Fever
• Spinal pain
• Weakness or paralysis in one, two, or all four legs

If the forebrain is primarily affected, response to immunosuppressive corticosteroids may be prolonged or rarely curative. If the hindbrain or spinal cord is primarily affected, drug therapy is less successful for complete or long-lasting improvement.

The onset of GME is usually acute with a slowly, insidious progression over one to two months. Even with therapy, the usual survival of dogs with GME is less than 12 months.

Diagnosis of GME in Dogs

The diagnosis of GME requires microscopic examination of affected CNS tissue, which is rarely practical. Your veterinarian will perform a complete physical and neurologic examination and may order some additional tests, such as:

• Complete blood count or hemogram
• Serum chemistry analysis
• Urinalysis

Depending on the results of the individual tests above, other test may be required and could include:

• Neuroimaging (CT and/or MRI)
• Cerebrospinal fluid (CSF) analysis
• Electroencephalogram
• Bacterial and viral culture of CSF
• Serological testing of the blood

Treatment of GME in Dogs

The general goals of treatment are to provide supportive care and relieve symptoms. Specific treatment may include:

• Anticonvulsants such as phenobarbital to treat seizures
• Corticosteroids such as dexamethazone or prednisone to immunosuppress the body and prevent further destruction of brain parenchyma caused by the disease.
• Supportive care (rest, nutrition, fluids) to fight the inflammation. If your pet cannot tolerate medications, food, or fluids orally, some of these things can be given intravenously.

Home Care

If your pet has been diagnosed with GME, follow your veterinarian’s treatment recommendation and notify him if any symptoms worsen or emergency symptoms appear.

Keep your pet well-rested, warm, and well fed following the illness. Maintain a stress-free environment.

GME has an overall poor prognosis for long-term recovery. Treatment is aimed at prolonging an excellent quality of life.