Latest development in the medicinal treatment of dogs presumptively diagnosed with granulomatous meningoencephalitis

Abstract

Granulomatous meningoencephalitis (GME) is a non-suppurative inflammatory disease that affects the central nervous system (CNS) of dogs. It is characterized histologically by the formation of large perivascular cuffs of mononuclear cells in the parenchyma and meninges of the brain and/or spinal cord. GME can affect any breed or age, however, young to middle-aged dogs, females and small purebreds such as toy and terrier breeds and Poodles tend to be overrepresented. Clinical and neurological symptoms of GME often have an acute and rapidly progressive onset, which will be fatal if left untreated. Based on morphological and clinical neurologic abnormalities, three forms of GME have been described; disseminated/multifocal, focal and ocular/ophthalmic form. Clinical signs vary greatly because they reflect the arrangement and location of the CNS lesion. The aetiopathogenesis of the disease remains unknown, although immunemediated mechanism is suspected. GME can only be definitely diagnosed by brain biopsy or post mortem histopathological evaluation of brain tissue. It is therefore commonly referred to as meningoencephalitis of unknown aetiology (MUE), which comprises all canine CNS inflammatory diseases for which there are no histopathological confirmation and no infectious cause have been identified. High dose, long-term immunosuppression has been proven to be the key to a successful therapy. Corticosteroids (primarily prednisone) have been the mainstay of treatment, but due to significant adverse effects, high possibility of relapse and short survival times, new and more effective treatment protocols have been suggested. More recently, supplemental immunosuppressive drugs have been employed in an attempt to prolong survival times and increase the quality of life. A review of azathioprine, cyclosporine, cytosine arabinoside, lomustine, leflunomide and procarbazine as adjunctive immunomodulatory agents is provided in this thesis. Also included in this thesis are case reports of 9 dogs presumptively diagnosed with GME. Their treatment regimes are different, but a common denominator is that more than one supplemental immunomodulatory drug was used. All dogs are still alive and 8/9 dogs are without any medications and living a symptom free life. Even though the results of these case reports are inadequate to be considered as scientific data, it opens up possibilities of a more favourable long-term outcome.