Magnetic resonance imaging and pathological findings in a case of canine idiopathic eosinophilic meningoencephalitis.

A case of idiopathic eosinophilic meningoencephalitis in a six-month-old male Maremma shepherd dog is reported. The dog was referred with a four month history of progressive weakness and depression with loss of trained habits. Tendency to recumbency, disorientation, visual impairment, bilaterally decreased menace response and hindlimb conscious proprioception deficits were detected. Magnetic resonance imaging showed a diffuse hypointense signal involving the cerebral grey matter with enlargement of the cerebral sulci on T1-weighted and fast fluid-attenuated inversion recovery (FLAIR) sequences consistent with a diffuse necrosis or atrophy of the cortical grey matter. Histological examination revealed severe inflammatory infiltration mainly composed of eosinophils and macrophages in the subarachnoid space and in the superficial layer of the cerebral cortex where parenchymal rarefaction and necrosis of neurones were also evident. No parasites, cysts or fungi were detected, and an immunologically mediated disorder was suspected. Magnetic resonance imaging may represent a useful diagnostic tool to differentiate idiopathic eosinophilic meningoencephalitis from other inflammatory brain diseases of young dogs.