Affects: Cats, Dogs
Granulomatous meningoencephalitis (GME) is an inflammatory disease of the central nervous system (CNS) of dogs and, rarely, cats. It is a form of meningoencephalitis. GME is likely second only to encephalitis caused by canine distemper virus as the most common cause of inflammatory disease of the canine CNS. The disease is more common in female dogs of young and middle age. It has a rapid onset. The lesions of GME exist mainly in the white matter of the cerebrum, brainstem, cerebellum, and spinal cord. The cause is only known to be noninfectious and is considered at this time to be idiopathic. Because lesions resemble those seen in allergic meningoencephalitis, GME is thought to have an immune-mediated cause, but it is also thought that the disease may be based on an abnormal response to an infectious agent. One study searched for viral DNA from canine herpesvirus, canine adenovirus, and canine parvovirus in brain tissue from dogs with GME, necrotizing meningoencephalitis, and necrotizing leukoencephalitis (see below for the latter two conditions), but failed to find any.
Diagnosis And Treatment: Cerebrospinal fluid (CSF) analysis shows a large number of white blood cells. Typically small mature lymphocytes are the majority of cells seen, with monocytes and neutrophils making up the rest. Definitive diagnosis is based on histopathology, either a brain biopsy or post-mortem evaluation (necropsy). A CT scan or MRI will show patchy, diffuse, or multifocal lesions. For a number of years, the basic treatment was some type of corticosteroid in combination with one or more immunosuppressive drugs, typically cytosine arabinoside and/or cyclosporine or other medications such as azathioprine, cyclophosphamide, or procarbazine, of which were usually added one at a time to the corticosteroid until a successful combination was found. There is evidence that treatment with radiation therapy for focal GME provides the longest periods of remission.