Eosinophilic Cerebrospinal Fluid Pleocytosis in A Dog With Hypertrophic Pachymeningitis and Generalized Eosinophilic Disease

An 8-year-old Whippet crossbreed was presented with a month's history of collapsing episodes and altered mentation. Clinical improvement was noted upon administration of prednisolone prior to referral. Neurologic examination was compatible with a multifocal intracranial disease. Magnetic resonance imaging revealed thickening of the dura mater around the left parietal and temporal cerebral cortex, left piriform lobe, and cerebellar hemispheres. Cerebrospinal fluid (CSF) analysis revealed marked eosinophilic pleocytosis with increased protein concentration. Infectious diseases were ruled out. Thoracic and abdominal imaging did not reveal any significant abnormalities. The dog was euthanized 4 days after diagnosis. Post-mortem examination revealed diffuse, severe, subacute to chronic eosinophilic pachymeningitis and generalized eosinophilic disease. Eosinophilic CSF pleocytosis has been reported in a number of inflammatory (sterile and infectious) and neoplastic canine encephalopathies. To the best of our knowledge, eosinophilic pleocytosis has not been reported in cases of hypertrophic pachymeningitis in dogs.