Clinical presentation and magnetic resonance imaging findings in 11 dogs with eosinophilic meningoencephalitis of unknown aetiology.

OBJECTIVES: To describe the clinical presentation, MRI findings and outcome in dogs with eosinophilic meningoencephalitis of unknown origin.
MATERIALS AND METHODS: Dogs were included in this retrospective study if they had complete medical records, complete neurological examination, MR imaging, cerebellomedullary cerebrospinal fluid sample consistent with eosinophilic pleocytosis and negative infectious disease testing.
RESULTS: Eleven dogs were included with a median age of 22·0 months (range 7·6 to 92·0 months). Nine breeds were represented. Neurological abnormalities included obtundation (n=10), menace response deficits (n=9), proprioceptive deficits (n=7), ataxia (n=7) and seizures (n=2). Neuroanatomical localisation was multi-focal (n=4), central vestibular system (n=4), diffuse forebrain (n=2) or left trigeminal/facial nerves (n=1). Seven dogs had peripheral eosinophilia. Ten dogs had bilateral symmetrical lesions affecting the cortical grey matter, which was hyperintense on T2-weighted and fluid-attenuating inversion recovery images and iso- to hypointense on T1-weighted images with associated meningeal contrast enhancement. MRI findings were consistent with diffuse meningitis and atrophy or necrosis of cortical grey matter. One dog had increased contrast uptake in the left trigeminal nerve. Ten dogs receiving corticosteroids survived to discharge, with seven also receiving cytarabine arabinoside. Median survival time was 762 days. CLINICAL SIGNIFICANCE: Eosinophilic meningoencephalitis of unknown origin affects younger larger-breed dogs, with the majority having suspected diffuse cerebrocortical meningitis and cortical (polio)encephalitis, which can be identified on MRI. Response to immunosuppressive treatment is good in the medium to long term, although further studies are required in this area.