Novel Magnetic Resonance Imaging Findings of Bilaterally Symmetrical Lesions in a Dog With Concomitant Granulomatous Meningoencephalitis and Necrotizing Encephalitis.

A 3-year-old, female neutered Bichon Frise was presented with a 2-day history of behavioral changes and ataxia. The neurological examination was consistent with diffuse forebrain involvement, with left lateralization. An MRI study identified bilaterally symmetrical T2W/T2 fluid-attenuated inversion recovery (T2-FLAIR) hyperintense, T1W hypointense, non-enhancing lesions involving the basal nuclei, with restricted diffusion and hemorrhage affecting both caudate nuclei. Similar bilaterally symmetrical T2W/T2-FLAIR hyperintense lesions were noted in the hypothalamus, midbrain, and occipital lobes. Histopathological examination indicated concomitant granulomatous meningoencephalitis and necrotizing encephalitis. This case report documents previously unreported bilaterally symmetrical canine brain lesions suspected to be secondary to an autoimmune inflammatory etiology.