GRANULOMATOUS MENINGOENCEPHALOMYELITIS

About the Diagnosis

Granulomatous meningoencephalomyelitis (GME) is a disease of the brain and spinal cord (central nervous system) of dogs. The fundamental problem is inflammation (-itis) of the lining of the brain and spinal cord (meninges) and the brain (encephalo) and spinal cord (myel). The cause of GME is unknown, but an altered response of the body to infectious agents or an inadvertent, self-targeted attack by the body's own immune system are suspected. Regardless of specific trigger, the damage is done by the body's own system of inflammation being overly active in and around the brain, which is harmful.

Dogs with GME are most often between 1 and 9 years of age, and female dogs, small breed dogs, poodles, poodle mixes, and Airedale terriers are more likely to be affected than other dogs. Granulomatous meningoencephalomyelitis occurs in one of two forms: focal, where the signs can be localized to one area of the brain or spinal cord, or multifocal/disseminated, where multiple areas of the nervous system are affected. The word granulomatous refers to the type of chronic inflammation seen in brain tissue samples when they are examined microscopically.

This disease is confined to the central nervous system (brain and spinal cord), and a variety of symptoms can occur, depending upon the part of the brain or spinal cord involved. Possible symptoms include seizures, blindness, walking aimlessly in circles, holding the head in a tilted position, weakness or paralysis, reluctance to move, and neck pain. These symptoms appear suddenly, although in the focal form, the disease often progresses more slowly (and symptoms may appear more gradually, over a period of days or weeks) than in the disseminated form.

There are many causes of these types of symptoms, and adequate treatment depends on identifying which one is present. Basic information necessary for assessing the possibility of other, "impostor" syndromes that mimic GME but are totally different include: information from you regarding duration and type of symptoms observed; physical and neurologic examination performed by the veterinarian; routine blood and urine tests; and routine x-rays and ultrasound exams of the chest and abdomen in some cases. The primary diagnostic test for determining whether GME is present or not is examination of cerebrospinal fluid. For this test, the pet is anesthetized to prevent movement and to avoid pain. A spinal tap is performed, during which a small needle is inserted into the space around the spinal cord, either at the base of the skull or at the lower back. A small amount of spinal fluid is withdrawn and submitted for microscopic examination and laboratory testing. The spinal fluid of dogs with granulomatous meningoencephalomyelitis has characteristic abnormalities that set it apart from other types of central nervous system diseases. Imaging studies, such as myelograms, MRI, or CT scans, are also sometimes used, especially in cases of focal disease. To eliminate infectious disease as a cause of the symptoms, since both the symptoms and the spinal fluid from severe infections can be similar to those for GME, specialized blood screens for certain infections and spinal fluid bacterial or fungal cultures may be necessary. Such extensive testing is typically necessary because GME is an incurable, progressive disease. It can be treated with medications to improve/reduce symptoms, but it is preferable to find another, curable problem as the cause of symptoms instead, and this is one of the main purposes of the diagnostic medical tests listed above.

Living with the Diagnosis

The range of response to medications and outcome is extremely broad: some dogs respond to treatment and survive for months, or even years, while others die within days to weeks, despite treatment. One of the most important determinants of how a dog will do is its response to initial treatment after the diagnosis of GME has been confirmed with a spinal tap.

Treatment

Since the fundamental problem is a misdirected immune attack on the brain tissue, immunosuppressive therapy helps some dogs. High doses of corticosteroids (cortisone-like medications) are given to try to reduce the degree of immune-mediated damage. These medications can be given as tablets by mouth at home. In dogs that respond favorably, treatment is lifelong. Discontinuation of treatment can result in a relapse of the disease. If corticosteroids are not tolerated by the pet or are ineffective, other immunosuppressive drugs can be tried. In some cases, radiation therapy may be effective for dogs with the focal form of granulomatous meningoencephalomyelitis. Severely affected or unstable pets may need to be hospitalized for initial treatment, and the degree to which any pet responds to treatment is highly variable and cannot be predicted.

DOs

• Realize that GME is a serious but potentially manageable disease that almost always requires lifelong treatment.

• Be attentive to the specific needs of a pet with GME: vision loss and possible disorientation mean that certain situations should be avoided. Examples of activities or circumstances that a pet with GME should avoid include: walking beside steep drops (long flight of stairs, edge of a cliff), swimming in deep water, and any other situation where decreased vision or impaired mental function could pose a serious threat.

• Give the medication as directed, and if you notice an increase in panting, restlessness, and excessive drinking and urinating, realize that these may be medication-related, not pain or discomfort. If such symptoms appear excessive, you should notify your veterinarian, and an alternative treatment approach may be preferable.

DON'Ts

• Do not discontinue corticosteroid treatment abruptly. This is likely to cause a relapse.

When to Call Your Veterinarian

• If your pet's symptoms worsen.

Signs to Watch For

• Seizures.
• Weakness or paralysis of the limbs.
• Neck pain or reluctance to move.
• Blindness.
• Circling, head tilt, or pressing the head against walls.

Routine Follow-Up

• Dogs on immunosuppressive therapy will need periodic examinations and laboratory testing to detect possible side effects of treatment.