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. Types of GME Disseminated – This is a diffuse disease throughout the CNS. It was previously known as inflammatory reticulosis. There is an accumulation of mononuclear cells and neutrophils around the blood vessels (perivascular) of the CNS. Meningitis is seen with this form of GME and causes fever and neck pain. It has an acute progression over a few weeks. Symptoms include incoordination, nystagmus, head tilt, seizures, and depression. Focal – The disease presents as a granuloma, which mimics a tumor. It usually is found in the cerebrum or cerebellopontine angle. Symptoms may be acute or develop slowly over several months and depend on the location of the lesion. Ocular – This is an uncommon form of GME and is characterized by sudden blindness caused by optic neuritis. The disease is bilateral. Ocular GME is considered to be an extension of CNS disease. The blood vessels of the posterior segment of the eye and anterior uvea have the same infiltrates of inflammatory cells as the intracranial vessels. Uveitis, retinal detachment, and secondary glaucoma may be seen. 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