Meningoencephalitis of unknown origin following a diagnosis of idiopathic generalised tremor syndrome in a dog

Abstract A 3‐year‐old, female, neutered Podenco Canario presented with neurological deterioration following 6 months of treatment for idiopathic generalised tremor syndrome. The dog was initially presented with hypermetric, ataxia, generalised tremors and opsoclonus. Magnetic resonance imaging of the head was normal, and cerebrospinal fluid analysis showed mild pleocytosis. Idiopathic generalised tremor syndrome was diagnosed. Immunosuppressive treatment with a tapering scheme of prednisolone was initiated, and later, cyclosporine was added. After 6 months, during immunosuppressive treatment, neurological deterioration was noticed. New signs included aggressive behaviour, leftward drifting and oromandibular dystonia/dysphagia. Follow‐up magnetic resonance imaging revealed multifocal intra‐axial lesions affecting mainly white matter in the frontal and parietal lobes, thalamus and brainstem, suggestive of meningoencephalitis of unknown origin. Cerebrospinal fluid re‐examination indicated mild mononuclear pleocytosis. Immunosuppressive dosage was increased with a satisfactory long‐term outcome. In both idiopathic generalised tremor syndrome and meningoencephalitis of unknown origin, an immune‐mediated cause is suspected. The progression from idiopathic generalised tremor syndrome to meningoencephalitis of unknown origin has not been previously reported.